Plants and insect eggs: how do they affect each other?

Influence of Bemisia tabaci-Induced Plant Volatiles on the Host-Choice Behavior of Tuta absoluta

Plants respond to attacks by insects by releasing herbivore-induced plant volatiles (HIPVs), which are known to influence the behavior of natural enemies, conspecific and heterospecific insects. However, little is known about how HIPVs induced by one insect species influence the behavior of an allospecific insect species, particularly if these insects belong to different feeding guilds. Here, using the interaction of two co-occurring insects with different feeding guilds - Bemisia tabaci (a sap sucking insect) and Tuta absoluta (a leaf mining insect) - on potato plants, we report that T. absoluta significantly preferred potato plants infested by B. tabaci. This preference is attributed to the B. tabaci-induced potato plant volatiles. Gas chromatography coupled with mass spectroscopy (GC-MS) analysis further revealed notable alterations in volatile composition between B. tabaci-infested and uninfested plants. Additionally, gas chromatography coupled with electroantennogram detector (GC-EAD) analysis identified four compounds - undecane, β-caryophyllene, β-farnesene and germacrene D - in B. tabaci-induced potato plant volatiles that elicited responses from T. absoluta antennae. Our findings emphasize how B. tabaci infestation alters potato plant volatile composition, making them attractive to T. absoluta. Understanding the chemical ecology interactions between allospecific insects with different feeding guilds is crucial for understanding how different insect groups affect the host location of one another through HIPVs. This knowledge can contribute to the development of more effective pest management strategies against these economically important pests.

Structural characterization and proteomic profiling of oviposition secretions across three rice planthopper species

Insect oviposition secretions play crucial roles during the reproductive process, yet systematic studies on their structural characterization and protein compositions remain limited. This study investigated the oviposition secretions of three major rice pests: the brown planthopper (Nilaparvata lugens, BPH), small brown planthopper (Laodelphax striatella, SBPH), and white-backed planthopper (Sogatella furcifera, WBPH). Ultrastructural observation revealed differences in the oviposition secretions of them. The eggs of BPH and SBPH were adhered to rice tissue by abundant secretions, while WBPH eggs were embedded deeper within the leaf sheath with less secretions. Proteomic analysis identified 111, 98, and 66 oviposition secretion proteins (OSPs) in BPH, SBPH, and WBPH, respectively. 4 common protein subgroups were shared among them, along with varying numbers of shared subgroups between species pairs. Notably, the majority of OSPs were exclusively found in one species, indicating the existence of both similar and specialized functions unique to each planthopper species. The functions of 4 uncharacterized OSPs (Nl.chr07.0363, Nl.chr12.078, Nl.chr11.716, Nl.scaffold.0714) that were uniquely identified in the BPH were studied by maternal RNAi. Downregulation of each of these 4 protein-coding genes led to a significant decrease in egg production and hatchability. Moreover, knockdown of Nl.chr12.078 or Nl.chr07.0363 also disrupt the secretory function of the lateral oviduct. In conclusion, this study provides insights into the structural characteristics and protein components of the oviposition secretions of BPH, SBPH, and WBPH, which could serve as potential targets for RNAi-based pest control and lay a foundation for future studies on insect-plant interactions mediated by oviposition secretions.

Anatomical and Metabolome Features of Haloxylon aphyllum and Haloxylon persicum Elucidate the Resilience against Gall-Forming Insects

Globally, gall-forming insects significantly contribute to the degradation of desert ecosystems. Recent studies have demonstrated that Haloxylon persicum suffers less damage from gall-formers compared to Haloxylon aphyllum. However, the mechanisms driving the long-term metabolic responses of these species to gall-forming biotic stress in their natural environment remain unclear. The current study comparatively analyzes the anatomical features and metabolomic changes in H. aphyllum and H. persicum damaged by gall-forming insects. This research aimed to uncover potential metabolic tolerance mechanisms through GC-MS analysis. The study findings indicate that gall-forming insects cause a reduction in nearly all the anatomical structures of Haloxylon shoots, with the effects being less severe in H. persicum than in H. aphyllum. Thus, the metabolic pathways responsible for the biosynthesis of biologically active substances that enhance resistance to gall inducers were different, specifically in H. aphyllum-the biosynthesis of fatty acids (+their derivatives) and γ-tocopherol (vitamin E) and H. persicum-the biosynthesis of fatty acids (+their derivatives), dialkyl ethers, carbohydrates (+their derivatives), aromatic acid derivatives, phytosterols, γ-tocopherol (vitamin E), phenols, and terpenoids. The results suggest that the modulation of metabolic pathways under biotic stress plays a crucial role in the enhanced survival and growth of H. persicum.

Plant defensive responses to insect eggs are inducible by general egg-associated elicitors

Egg deposition by herbivorous insects is well known to elicit defensive plant responses. Our study aimed to elucidate the insect and plant species specificity of these responses. To study the insect species specificity, we treated Arabidopsis thaliana with egg extracts and egg-associated secretions of a sawfly (Diprion pini), a beetle (Xanthogaleruca luteola) and a butterfly (Pieris brassicae). All egg extracts elicited salicylic acid (SA) accumulation in the plant, and all secretions induced expression of plant genes known to be responsive to the butterfly eggs, among them Pathogenesis-Related (PR) genes. All secretions contained phosphatidylcholine derivatives, known elicitors of SA accumulation and PR gene expression in Arabidopsis. The sawfly egg extract did not induce plant camalexin levels, while the other extracts did. Our studies on the plant species specificity revealed that Solanum dulcamara and Ulmus minor responded with SA accumulation and cell death to P. brassicae eggs, i.e. responses also known for A. thaliana. However, the butterfly eggs induced neoplasms only in S. dulcamara. Our results provide evidence for general, phosphatidylcholine-based, egg-associated elicitors of plant responses and for conserved plant core responses to eggs, but also point to plant and insect species-specific traits in plant-insect egg interactions.

Temperature alters the toxicological impacts of plant terpenoids on the polyphagous model herbivore Vanessa cardui

Terpenes are a major class of secondary metabolites present in all plants, and long hypothesized to have diversified in response to specific plant-herbivore interactions. Herbivory is a major biotic interaction that plays out across broad temporal and spatial scales that vary dramatically in temperature regimes, both due to climatic variation across geographic locations as well as the effect of seasonality. In addition, there is an emerging understanding that global climate change will continue to alter the temperature regimes of nearly every habitat on Earth over the coming centuries. Regardless of source, variation in temperature may influence herbivory, in particular via changes in the efficacy and impacts of plant defensive chemistry. This study aims to characterize temperature-driven variation in toxicological effects across several structural classes of terpenes in the model herbivore Vanessa cardui, the painted lady butterfly. We observed a general increase in monoterpene toxicity to larvae, pupa, and adults at higher temperatures, as well as an increase in development time as terpene concentration increased. Results obtained from this study yield insights into possible drivers of seasonal variation in plant terpene production as well as inform effects of rising global temperatures on plant-insect interactions. In the context of other known effects of climate change on plant-herbivore interactions like carbon fertilization and compensatory feeding, temperature-driven changes in plant chemical defense efficacy may further complicate the prediction of climate change impacts on the fundamental ecological process of herbivory.

Defense Strategies of Rice in Response to the Attack of the Herbivorous Insect, Chilo suppressalis

Chilo suppressalis is a notorious pest that attacks rice, feeding throughout the entire growth period of rice and posing a serious threat to rice production worldwide. Due to the boring behavior and overlapping generations of C. suppressalis, the pest is difficult to control. Moreover, no rice variety with high resistance to the striped stem borer (SSB) has been found in the available rice germplasm, which also poses a challenge to controlling the SSB. At present, chemical control is widely used in agricultural production to manage the problem, but its effect is limited and it also pollutes the environment. Therefore, developing genetic resistance is the only way to avoid the use of chemical insecticides. This article primarily focuses on the research status of the induced defense of rice against the SSB from the perspective of immunity, in which plant hormones (such as jasmonic acid and ethylene) and mitogen-activated protein kinases (MAPKs) play an important role in the immune response of rice to the SSB. The article also reviews progress in using transgenic technology to study the relationship between rice and the SSB as well as exploring the resistance genes. Lastly, the article discusses prospects for future research on rice's resistance to the SSB.

Cradle for the newborn Monochamus saltuarius: Microbial associates to ward off entomopathogens and disarm plant defense

The Japanese pine sawyer, Monochamus saltuarius, as a beetle vector of Bursaphelenchus xylophilus (pine wood nematode), is an economically important forest pest in Eurasia. To feed on the phloem and xylem of conifers, M. saltuarius needs to overcome various stress factors, including coping with entomopathogenic bacteria and also various plant secondary compounds (PSCs). As an important adaptation strategy to colonize host trees, M. saltuarius deposit eggs in oviposition pits to shield their progeny. These pits harbor bacterial communities that are involved in the host adaptation of M. saltuarius to the conifers. However, the composition, origin, and functions of these oviposition pit bacteria are rarely understood. In this study, we investigated the bacterial community associated with M. saltuarius oviposition pits and their ability to degrade PSCs. Results showed that the bacterial community structure of M. saltuarius oviposition pits significantly differed from that of uninfected phloem. Also, the oviposition pit bacteria were predicted to be enriched in PSC degradation pathways. The microbial community also harbored a lethal strain of Serratia, which was significantly inhibited. Meanwhile, metatranscriptome analysis indicated that genes involved in PSCs degradation were expressed complementarily among the microbial communities of oviposition pits and secretions. In vitro degradation showed that bacteria cultured from oviposition pits degraded more monoterpenes and flavonoids than bacteria cultured from uninfected phloem isolates. Disinfection of oviposition pits increased the mortality of newly hatched larvae and resulted in a significant decrease in body weight in the early stages. Overall, our results reveal that M. saltuarius construct oviposition pits that harbor a diverse microbial community, with stronger PSCs degradation abilities and a low abundance of entomopathogenic bacteria, resulting in the increased fitness of newly hatched larvae.

Morphology of the Antennal Sensilla of the Nymphal Instars and Adults in Notobitus meleagris (Hemiptera: Heteroptera: Coreidae)

The bamboo bug Notobitus meleagris (Fabricius, 1787) is a serious pest of bamboo shoots in China, India, Myanmar, Vietnam, and Singapore. The antennae of the nymphal instars and adults of N.meleagris are involved in communication among individuals and finding the host plants. In order to understand the morphology of antennal sensilla, their types, and the distribution of sensilla on the antennae of nymphal instars and adults in N. meleagris, we studied the morphology of antennal sensilla with a scanning electron microscope. The antennae of the nymphs and adults comprised the scape, pedicel, and two flagellomeres. Four types and eight subtypes of sensilla were identified in the nymphal instars (sensilla trichodea [St].1, St.2, St.3, sensilla basiconica [Sb].1, Sb.2, sensilla chaetica [Sc].1, Sc.2, sensilla coeloconica [Sco].1), whereas those of the adults had five types and eleven subtypes of sensilla (St.1, St.2, St.3, Sb.1, Sb.2, Sb.3, Sc.1, Sc.2, Sco.1, Sco.2, and sensilla campaniformia [Sca]). There are significant differences in the number, type, and size of the sensilla in different nymphal instars, which increases with the increase in nymphal instars. There was no sexual dimorphism observed in the adult sensilla; however, the length and diameter of St.3, Sb.2, and Sb.3 were sexually dimorphic. The potential functions of each sensillum were discussed based on the morphology and distribution of the antennal sensilla and were compared with similar published studies. Our results provide primary data for further research on the behavioral mechanism, green prevention, and control of N. meleagris.

Sawfly egg deposition extends the insect life cycle and alters hormone and volatile emission profiles

Introduction

Insect oviposition can enhance plant defenses and decrease plant quality in response to future feeding damage by hatched larvae. Induced resistance triggered by egg deposition and its negative effect on insect herbivore performance is known for several annual plants but has been much less studied in woody perennials, such as species of the Salicaceae. Here we studied the response of the willow Salix babylonica to oviposition by the specialist willow sawfly Nematus oligospilus and its impact on insect performance.

Methods

We measured the effect of oviposition on larval feeding and pupa formation and evaluated its influence on plant phytohormones and volatile emission profile.

Results

We showed that oviposition reduced neonate larval growth and increased the proportion of prepupae that delayed their transition to pupae, thus extending the length of the sawfly cocoon phase. Oviposited willows increased jasmonic acid levels and changed their volatile profile through enhanced concentrations of the terpenoids, (E/E)-α-farnesene, (Z)- and (E)-β-ocimene. Volatile profiles were characteristic for each type of insect damage (oviposition vs. feeding), but no priming effect was found.

Discussion

We demonstrated that willows could perceive sawfly oviposition per se as a primary factor activating defense signaling via the jasmonic acid pathway. This induced response ultimately determined changes in pupation dynamics that may affect the whole insect population cycle.

Assessment of the Molecular Responses of an Ancient Angiosperm against Atypical Insect Oviposition: The Case of Hass Avocados and the Tephritid Fly Anastrepha ludens

Anastrepha spp. (Diptera: Tephritidae) infestations cause significant economic losses in commercial fruit production worldwide. However, some plants quickly counteract the insertion of eggs by females by generating neoplasia and hindering eclosion, as is the case for Persea americana Mill., cv. Hass (Hass avocados). We followed a combined transcriptomics/metabolomics approach to identify the molecular mechanisms triggered by Hass avocados to detect and react to the oviposition of the pestiferous Anastrepha ludens (Loew). We evaluated two conditions: fruit damaged using a sterile pin (pin) and fruit oviposited by A. ludens females (ovi). We evaluated both of the conditions in a time course experiment covering five sampling points: without treatment (day 0), 20 min after the treatment (day 1), and days 3, 6, and 9 after the treatment. We identified 288 differentially expressed genes related to the treatments. Oviposition (and possibly bacteria on the eggs' surface) induces a plant hypersensitive response (HR), triggering a chitin receptor, producing an oxidative burst, and synthesizing phytoalexins. We also observed a process of cell wall modification and polyphenols biosynthesis, which could lead to polymerization in the neoplastic tissue surrounding the eggs.

Ultrastructure Characteristics and Sexual Dimorphism of Antennal Sensilla in Tirathaba rufivena (Lepidoptera: Pyralidae)

Tirathaba rufivena Walker, a major insect pest of Areca catechu L., has severely threatened areca nut cultivation in Hainan, China. To improve our understanding of the communication mechanism in host plant seeking and mate-finding for T. rufivena, we described and further characterized the external morphology and internal sensilla structures using scanning electron microscopy and transmission electron microscopy in this study. The antennal morphology was similar between males and females, and there was no significant difference in length between the two sexes. In total, nine sensilla types were identified: sensilla trichodea (Str), sensilla chaetica (Sch), sensilla basiconica (Sba), sensilla auricillica (Sau), sensilla coeloconica (Sco), sensilla styloconica (Sst), Böhm sensilla (Bs), uniporous peg sensilla (Ups) and sensilla squamiformia (Ssq). Sexual dimorphism mainly occurs in variation in the length of Sba, Sch, Sco1 and Bs, and the abundance of Sba, Sau1 and Sau2. The Sba had larger size and numbers on female antennae than that on males, suggesting that these sensilla might have important roles in locating host plants. Both Sau1 and Sau2 were significantly more abundant in females and were probably associated with the detection of mates and host plant for oviposition. These data were important for ongoing studies on host plant seeking and mate-finding behavior in T. rufivena and provided a theoretical foundation to further studies of semiochemical control for this pest.

Pollen beetle offspring is more parasitized under moderate nitrogen fertilization of oilseed rape due to more attractive volatile signal

Biocontrol providing parasitoids can orientate according to volatile organic compounds (VOCs) of their host's plants, the emission of which is potentially dependent on the availability of soil nitrogen (N). This paper aimed at finding the optimal N fertilization rate for oilseed rape (Brassica napus L.) to favor parasitism of pollen beetles (Brassicogethes aeneus Fab. syn. Meligethes aeneus Fab.) in a controlled environment. Pollen beetles preferred to oviposit into buds of plants growing under higher N fertilization, whereas their parasitoids favored moderate N fertilization. As a part of induced defense, the proportion of volatile products of glucosinolate pathway in the total oilseed rape VOC emission blend was increased. Our results suggest that the natural biological control of pollen beetle herbivory is best supported by moderate N fertilization rates.

Oviposition by a Specialist Herbivore Increases Susceptibility of Canola to Herbivory by a Generalist Herbivore

Oviposition by specialist herbivores can alter the suitability of the host plant to subsequent infestation by other herbivores. In this study, we tested the effect of previous oviposition on canola, Brassica napus L., by a Brassica specialist, the diamondback moth (DBM), Plutella xylostella (L.) (Lepidoptera: Plutellidae), on subsequent herbivory by the generalist feeder, the bertha armyworm (BAW), Mamestra configurata Walker (Lepidoptera: Noctuidae). The effect of DBM oviposition on subsequent BAW oviposition and larval feeding was tested in no-choice and choice experiments. Oviposition of BAW was not altered by DBM eggs on canola plants, however, BAW had increased larval feeding on plants with DBM eggs. These results suggest that oviposition by a specialist herbivore increased the susceptibility of the host plant to generalist herbivory. In a preliminary experiment, salicylic acid, jasmonic acid, and its conjugates were not altered by DBM oviposition on canola, however, further experimentation is needed to determine if oviposition affects expression of plant defense pathways and other plant traits.

Phytochemical-based nanodrug delivery in cancer therapy

There are estimated to be 13.1 million cancer deaths by 2030, with 7.6 million deaths occurring each year. Phytochemicals have long been used in traditional medicine to cure cancer. However, conventional therapy for metastatic illness may fail if cancer cells become resistant to multiple anticancer drugs. Phytochemicals encapsulated in nano-based medication delivery devices were studied for their cancer- and chemo-preventive properties. Nanocarriers containing phytoconstituents have been studied in terms of loading efficiency, nanocarrier size, the release profile of the drug, and cell inhibition and treatment tests.

A comprehensive review on the documented characteristics of four Reticulitermes termites (Rhinotermitidae, Blattodea) of China

Termites are known as social insects worldwide. Presently in China 473 species, 44 genera and 4 families of termites have been reported. Of them, 111 Reticulitermes species are widely spread in different zones of China. The dispersion flight season of these Chinese Reticulitermes species are usually started from February to June, but in some regions different species are distributed, sharing their boundaries and having overlapping flight seasons. These reasons become important sources of hybridization between two different heterospecific populations of termites. It was confirmed that the fertilized eggs and unfertilized eggs of some Reticulitermes termites have the capacity of cleavage. While the unfertilized eggs of R. aculabialis, R. chinensis and R. labralis cleaved normally and the only R. aculabialis unfertilized eggs develop in embryos. While, the R. flaviceps and R. chinensis were observed with their abnormal embryonic development, and not hatching of eggs parthenogenetically. They were reported more threatening to Chinese resources as they propagate with parthenogenesis, hybridization and sexual reproduction. Eggshell and macrophiles of eggs play important roles in species identification and control. Although, they are severe pests and cause a wide range of damages to wooden structures and products in homes, buildings, building materials, trees, crops, and forests in China's Mainland.

The Resistance of Seven Host Plants to Tetranychus merganser Boudreaux (Acari: Tetranychidae)

Simple Summary

The red spider mite, Tetranychus merganser is one of the most economically important pests in papaya and prickle pear cactus cultivars, causing major damage to fruit and defoliation. In recent years, T. merganser has increased the number of its host plants. The mechanisms of resistance of a plant to herbivorous arthropod include antixenosis and antibiosis. Antixenosis refers to the plant mechanism to affect feeding and oviposition of arthropods; antibiosis refers to the plant capacity to affect the biology of the arthropod. The aim of this research is to assess antibiosis and antixenosis as resistance mechanisms in seven host plants (Thevetia ahouai, Carica papaya, Phaseolus vulgaris, Moringa oleifera, Pittosporum tobira, Helietta parvifolia, Capsicum annuum var. glabriusculum) to red spider mites. Oviposition and damage by feeding of T. merganser were greater on C. papaya than on the other host plants. The population growth of the spider mite was lower in P. tobira and T. ahouai than in the other host plants. Results based on the analysis of demographic parameters, food intake, survival and oviposition of T. merganser females suggest that P. tobira and T. ahouai were the most resistant to red spider mites, whereas C. papaya was the most susceptible of the seven host plants. The resistant plants can be studied as alternatives in the management of red spider mites.

Abstract

Red spider mites, Tetranychus merganser Boudreaux (Acari: Tetranychidae), is an agricultural pest that causes economic losses in papaya and nopal crops in Mexico. The aim of this research was to assess antibiosis and antixenosis as resistance mechanisms in seven host plants (Thevetia ahouai, Carica papaya, Phaseolus vulgaris, Moringa oleifera, Pittosporum tobira, Helietta parvifolia, Capsicum annuum var. glabriusculum) to red spider mites. Antixenosis was evaluated by non-preference for oviposition and feeding, antibiosis by infinitesimal rate of increase, finite rate of increase and doubling time, and the percentage of spider mites mortality. Oviposition and damage by feeding of T. merganser were significantly greater on C. papaya than on the other host plants. The growth rate of the spider mite was significantly lower in P. tobira and T. ahouai than in the other host plants. The percentage of hatched eggs of T. merganser was significantly higher in P. vulgaris than in the other plant species. Based on the demographic parameters, survival, food intake, and oviposition, these results indicated that compared with C. papaya, P. tobira and T. ahouai were more resistant. These results may be due to the fact that they were plants species of different families. The resistant plants can be studied as alternatives in the management of T. merganser.

Transcriptomic Landscape of Herbivore Oviposition in Arabidopsis: A Systematic Review

Herbivore oviposition produces all sorts of responses in plants, involving wide and complex genetic rearrangements. Many transcriptomic studies have been performed to understand this interaction, producing a bulk of transcriptomic data. However, the use of many transcriptomic techniques across the years, the lack of comparable transcriptomic context at the time of publication, and the use of outdated databases are limitations to understand this biological process. The current analysis intends to retrieve oviposition studies and process them with up-to-date techniques and updated databases. To reduce heterogeneities, the same processing techniques were applied, and Arabidopsis was selected to avoid divergencies on plant taxa stress response strategies. By doing so, we intended to understand the major mechanisms and regulatory processes linked to oviposition response. Differentially expressed gene (DEG) identification and co-expression network-based analyses were the main tools to achieve this goal. Two microarray studies and three RNA-seq analyses passed the screening criteria. The collected data pertained to the lepidopteran Pieris brassicae and the mite Tetranychus urticae, and covered a timeline from 3 to 144 h. Among the 18, 221 DEGs found, 15, 406 were exclusive of P. brassicae (72 h) and 801 were exclusive for the rest of the experiments. Excluding P. brassicae (72 h), shared genes on the rest of the experiments were twice the unique genes, indicating common response mechanisms were predominant. Enrichment analyses indicated that shared processes were circumscribed to earlier time points, and after 24 h, the divergences escalated. The response was characterized by patterns of time-dependent waves of unique processes. P. brassicae oviposition induced a rich response that shared functions across time points, while T. urticae eggs triggered less but more diverse time-dependent functions. The main processes altered were associated with hormonal cascades [e.g., salicilic acid (SA) and jasmonic acid (JA)], defense [reactive oxygen species (ROS) and glucosinolates], cell wall rearrangements, abiotic stress responses, and energy metabolism. Key gene drivers of the identified processes were also identified and presented. The current results enrich and clarify the information regarding the molecular behavior of the plant in response to oviposition by herbivores. This information is valuable for multiple stress response engineering tools, among other applications.

Spider mite egg extract modifies Arabidopsis response to future infestations

Transcriptional plant responses are an important aspect of herbivore oviposition studies. However, most of our current knowledge is derived from studies using Lepidopteran models, where egg-laying and feeding are separate events in time. Little is known regarding plant response to pests where females feed and oviposit simultaneously. The present study characterized oviposition-induced transcriptomic response of Arabidopsis to Tetranychus urticae egg extracts. Transcriptional evidence indicates that early events in plant response to the egg extract involve responses typical to biotic stresses, which include the alteration in the levels of Ca²⁺ and ROS, the modification of pathways regulated by the phytohormones jasmonic acid and ethylene, and the production of volatiles and glucosinolates as defence mechanisms. These molecular changes affect female fertility, which was significantly reduced when mites fed on plants pre-exposed to the egg extract. However, longer periods of plant exposure to egg extract cause changes in the transcriptional response of the plant reveal a trend to a decrease in the activation of the defensive response. This alteration correlated with a shift at 72 h of exposition in the effect of the mite feeding. At that point, plants become more susceptible and suffer higher damage when challenged by the mite.

Supplementing Blood Diet With Plant Nectar Enhances Egg Fertility in Stomoxys calcitrans

Stomoxys calcitrans (stable fly) is a cosmopolitan biting fly of both medical and veterinary importance. Unlike blood-feeding-related behavior of stable fly, its plant feeding, the fitness value, and the S. calcitrans-plant interaction are less understood. Here we show based on two chloroplast DNA genes, ribulose bisphosphate carboxylase large chain (rbcL) and the intergenic spacer gene trnH-psbA, that field-collected male and female stable flies fed on various plant species. We investigated the fitness cost of plant feeding using Parthenium hysterophorus, one of the plant species identified to have been fed on by the field-collected flies. Supplementation of blood feeding with a flowering P. hysterophorus plant as nectar source enhanced egg hatchability significantly as compared to blood alone, showing the fitness value of nectar supplementation. However, nectar supplementation did not affect the number of eggs laid or longevity of S. calcitrans as compared to flies that fed on blood alone. S. calcitrans maintained on sugar alone failed to lay eggs. The various plants stable flies fed on demonstrated chemodiversity with their own signature scent. The behavioral response of S. calcitrans to these signature compounds varied from strong attraction (γ-terpinene) to neutral (linalool oxide and myrcene) to repellency (butanoic acid). Our study demonstrated that stable flies feed on nectar, and plant nectar supplementation of blood feeding enhanced larval emergence. Thus, our result has implication in stable fly reproduction, survival, disease transmission, boosting laboratory colony, and the possibility of using plant-derived odors for mass trapping of stable fly, for instance, using γ-terpinene.

Host plants alter their volatiles to help a solitary egg parasitoid distinguish habitats with parasitized hosts from those without

When attacked by herbivores, plants emit volatiles to attract parasitoids and predators of herbivores. However, our understanding of the effect of plant volatiles on the subsequent behaviour of conspecific parasitoids when herbivores on plants are parasitized is limited. In this study, rice plants were infested with gravid females of the brown planthopper (BPH) Nilaparvata lugens for 24 hr followed by another 24 hr in which the BPH eggs on plants were permitted to be parasitized by their egg parasitoid, Anagrus nilaparvatae; volatiles from rice plants that underwent such treatment were less attractive to subsequent conspecific parasitoids compared to the volatiles from plants infested with gravid BPH females alone. Chemical analysis revealed that levels of JA and JA-Ile as well as of four volatile compounds-linalool, MeSA, α-zingiberene and an unknown compound-from plants infested with BPH and parasitized by wasps were significantly higher than levels of these compounds from BPH-infested plants. Laboratory and field bioassays revealed that one of the four increased chemicals-α-zingiberene-reduced the plant's attractiveness to the parasitoid. These results suggest that host plants can fine-tune their volatiles to help egg parasitoids distinguish host habitats with parasitized hosts from those without.

Chemical Cues Induced from Fly-Oviposition Mediate the Host-Seeking Behaviour of Fopius arisanus (Hymenoptera: Braconidae), an Effective Egg Parasitoid of Bactrocera dorsalis (Diptera: Tephritidae), within a Tritrophic Context

Fopius arisanus is a solitary endoparasitoid that parasitizes a variety of tephritid species. Native to the Indo-Australian region, it is currently exploited worldwide as a biological control agent due to its exceptional efficiency in reducing pest populations. The efficiency of any biological control program is affected by the host location ability of the parasitoids. The present study used a Y-tube olfactometer to test the behavioural responses of female F. arisanus to four fruit species which had undergone different types of damages: undamaged, damaged through Bactrocera dorsalis ovipositioning (i.e., infested), or different levels of mechanical damage. Our results suggest that F. arisanus females were significantly attracted to mangoes and pears (vs. purified air), regardless of their condition; however, whilst infested mangoes did not attract more female parasitoids compared to healthy or mechanically damaged fruits, infested pears attracted significantly more. For citrus fruits and peaches, oviposition damage caused them to be more attractive to parasitoid females. In terms of the longevity of the effects, infested mango fruits remained attractive for up to 5 days after infestation, whereas for infested peaches, pears, and citrus fruits, the attractiveness tended to decrease as time passed. Regarding mechanical damage, mango fruits that had undergone any intensity of damage were equally attractive to parasitoid females; however, peach and citrus fruits with high levels of mechanical damage were more attractive, and pears were found to be most attractive with slight mechanical damage. Additional to the above, we also tested the effect of insecticides on behavioural responses using mangoes. We found that the treatment of infested fruits with lambda-cyhalothrin and cypermethrin remained attractive to F. arisanus females, albeit to different extents, which is in contrast to spinosad, cyantraniliprole, and acetamiprid. Finally, we suggest that the host-searching behaviour of F. arisanus females is mainly mediated by oviposition-induced volatiles, either emitted from the fruit or left by the fruit fly.

Plant-mediated effects of ozone on herbivores depend on exposure duration and temperature

Abiotic stress by elevated tropospheric ozone and temperature can alter plants’ metabolism, growth, and nutritional value and modify the life cycle of their herbivores. We investigated how the duration of exposure of Sinapis arvensis plants to high ozone and temperature levels affect the life cycle of the large cabbage white, Pieris brassicae. Plants were exposed to ozone-clean (control) or ozone-enriched conditions (120 ppb) for either 1 or 5 days and were afterwards kept in a greenhouse with variable temperature conditions. When given the choice, P. brassicae butterflies laid 49% fewer eggs on ozone-exposed than on control plants when the exposure lasted for 5 days, but showed no preference when exposure lasted for 1 day. The caterpillars took longer to hatch on ozone-exposed plants and at lower ambient temperatures. The ozone treatment had a positive effect on the survival of the eggs. Ozone decreased the growth of caterpillars reared at higher temperatures on plants exposed for 5 days, but not on plants exposed for 1 day. Overall, longer exposure of the plants to ozone and higher temperatures affected the life cycle of the herbivore more strongly. With global warming, the indirect impacts of ozone on herbivores are likely to become more common.

Egg parasitoid exploitation of plant volatiles induced by single or concurrent attack of a zoophytophagous predator and an invasive phytophagous pest

Zoophytophagous insect predators can induce physiological responses in plants by activating defence signalling pathways, but whether plants can respond to facultative phytophagy by recruiting natural enemies remains to be investigated. In Y-tube olfactometer bioassays, using a system including a Vicia faba plant, the zoophytophagous predator Podisus maculiventris and the egg parasitoid Telenomus podisi, we first demonstrated that T. podisi females are attracted by broad bean plants damaged by feeding activity of P. maculiventris and on which host egg masses had been laid, while they are not attracted by undamaged plants or plants damaged by feeding activity alone. In a second experiment, we evaluated the impact of the invasive phytophagous pest Halyomorpha halys on this plant volatile-mediated tritrophic communication. Results showed that the invasive herbivorous adults do not induce plants to recruit the native egg parasitoid, but they can disrupt the local infochemical network. In fact, T. podisi females are not attracted by volatiles emitted by plants damaged by H. halys feeding alone or combined with oviposition activity, nor are they attracted by plants concurrently infested by P. maculiventris and H. halys, indicating the specificity in the parasitoid response and the ability of the invasive herbivore in interrupting the semiochemical communication between plants and native egg parasitoids. To the best of our knowledge, this is the first study showing that zoophytophagous predator attacks induce indirect plant defences similarly to those defence strategies adopted by plants as a consequence of single or concurrent infestations of herbivorous insects.

Tuta absoluta (Lepidoptera: Gelechiidae) Success on Common Solanaceous Species from California Tomato Production Areas

Tuta absoluta (Meyrick) is a devastating pest of tomato that has invaded many regions of the world. To date, it has not been detected in North America, but the pest reached Costa Rica in 2014 and seriously threatens the southern, southwestern, and western United States including California. Although the primary host of T. absoluta is tomato, several other species of Solanaceae may serve as alternative hosts. In our study, we aimed to assess the potential risk that other solanaceous crops and wild species that are often present in and around California tomato fields could serve as hosts. To accomplish this, we conducted greenhouse and laboratory studies to determine whether two common cultivars of fresh market tomato, two common cultivars of tomatillo, and the wild plants, Solanum nigrum L., Solanum sarrachoides (Sendtner), and Datura stramonium L., are suitable hosts for reproduction and development of the pest. According to our results, D. stramonium and tomatillo were unable to sustain T. absoluta larval development in either greenhouse studies or laboratory studies, and therefore, they are not likely to contribute to T. absoluta establishment during an invasion. On the contrary, the two other solanaceous weeds, S. nigrum and S. sarrachoides, share a similar potential as tomato to be reproductive and developmental hosts of T. absoluta, and might play an important role in the establishment of the pest in California.

Effect of oviposition by Bactrocera dorsalis on the antioxidant activity of orange juice

Among fruits and fruit products, oranges and orange juice are the most widely consumed worldwide. However, the effects of pest infestation of oranges on the quality of orange juice are not yet known. To evaluate the effect of the oriental fruit fly Bactrocera dorsalis on the antioxidant activity of orange juice, we measured changes in the vitamin C (Vc) concentration, total phenol content, and antioxidant activity of orange juice after the introduction of fruit fly eggs. Ten days after the eggs were introduced (larvae removed), the concentration of Vc in orange juice was 18.65 µg/mL, which was 9.16 µg/mL lower than that measured in healthy orange juice. In addition, the total phenol content decreased by 46.519 mg Gallic Acid Equivalents (GAE)/g to 9.748 mg GAE/g. Furthermore, the free-radical scavenging activity decreased from 22.297% to 5.393%. Correlation analysis indicated significant correlations between Vc concentration, total phenol content, and antioxidant activity of orange juice after B. dorsalis infestation. The decrease in Vc concentration, total phenol content and free-radical scavenging activity indicated that B. dorsalis changed the quality of orange juice by affecting the antioxidant activity of the juice after the oranges were infested.

Anthonomus grandis aggregation pheromone induces cotton indirect defence and attracts the parasitic wasp Bracon vulgaris

Insect-derived volatiles seem to provide reliable chemical cues that plants could employ to defend themselves. Here we investigated the effect of pheromone emission from a closely associated (Anthonomus grandis; boll weevil) and an unassociated (Tibraca limbativentris) herbivore on cotton volatile emission. Exposure to A. grandis aggregation pheromone induced cotton defence response by enhancing the emission of volatiles attractive to the natural enemy of A. grandis, the parasitic wasp Bracon vulgaris, but only when the pheromonal blend was complete (all four components). Individual components of A. grandis aggregation pheromone were not able to induce cotton plants to increase the release of volatiles. On the other hand, T. limbativentris sex pheromone did not induce any change in the cotton constitutive volatile profile. Our results support the hypothesis that plants are able to detect pheromones of tightly co-evolved herbivores. Moreover, A. grandis pheromone exposure induced similar volatile compounds to herbivore-induced cotton, such as linalool, (E)-ocimene, (E)-4,8-dimethylnona-1,3,7-triene (DMNT), and (E,E)-4,8,12-trimethyltrideca-1,3,7,11-tetraene (TMTT). We also showed that the larval ectoparasitoid B. vulgaris relies on boll weevil's aggregation pheromone and pheromone-induced plant volatiles as kairomones to locate suitable hosts.

Insect egg deposition renders plant defence against hatching larvae more effective in a salicylic acid-dependent manner

Plants can improve their antiherbivore defence by taking insect egg deposition as cue of impending feeding damage. Previous studies showed that Pieris brassicae larvae feeding upon egg-deposited Brassicaceae perform worse and gain less weight than larvae on egg-free plants. We investigated how P. brassicae oviposition on Arabidopsis thaliana affects the plant's molecular and chemical responses to larvae. A transcriptome comparison of feeding-damaged leaves without and with prior oviposition revealed about 200 differently expressed genes, including enhanced expression of PR5, which is involved in salicylic acid (SA)-signalling. SA levels were induced by larval feeding to a slightly greater extent in egg-deposited than egg-free plants. The adverse effect of egg-deposited wild-type (WT) plants on larval weight was absent in an egg-deposited PR5-deficient mutant or other mutants impaired in SA-mediated signalling, that is, sid2/ics1, ald1, and pad4. In contrast, the adverse effect of egg-deposited WT plants on larvae was retained in egg-deposited npr1 and wrky70 mutants impaired further downstream in SA-signalling. Oviposition induced accumulation of flavonols in WT plants with and without feeding damage, but not in the PR5-deficient mutant. We demonstrated that egg-mediated improvement of A. thaliana's antiherbivore defence involves SA-signalling in an NPR1-independent manner and is associated with accumulation of flavonols.

The natural history of oviposition on a ginkgophyte fruit from the Middle Jurassic of northeastern China

A distinctive pattern of oviposition lesions occurs on a ginkgoalean seed, Yimaia capituliformis, which likely was inflicted by a kalligrammatid lacewing with a long, sword-like, plant-piercing ovipositor. This newly recorded oviposition type, DT272, occurs in the 165 million-year-old Jiulongshan Formation, of Middle Jurassic age, in Northeastern China. DT272 consists from three to seven, approximately equally spaced lesions with surrounding callus tissue, the fabricator of which targeted fleshy outer and inner tissues of a ginkgophyte fruit. This distinctive damage also is known from the fleshy attachment pad surfaces of basal bennettitalean bracts. Examination of the life history of this probable ginkgoalean-kalligrammatid oviposition interaction indicates that the spacing of the eggs in substrate tissues disfavored inter-larval contact, but little can be said of defense and counterdefense strategies between the plant host and the newly hatched immatures.

Approaches for the isolation and identification of hydrophilic, light-sensitive, volatile and minor natural products

Water-soluble, volatile, minor and photosensitive natural products are yet poorly known, and this review discusses the literature reporting the isolation strategies for some of these metabolites.

Toxicity to, oviposition and population growth impairments of Callosobruchus maculatus exposed to clove and cinnamon essential oils

The use of plant essential oils has been shown to efficiently control insect pests of stored beans, significantly reducing the threats associated with synthetic insecticides. Here, we evaluated the potential of applications of essential oils of clove, Syzygium aromaticum L., and cinnamon, Cinnamomum zeylanicum L., to control Callosobruchus maculatus, considered as one of the most cosmopolitan pests of stored beans. Using four combinations of couples (i.e., unexposed couples, exposed females, exposed males, and exposed couples), we also evaluated how sublethal exposure to these essential oils impacted C. maculatus oviposition. Bioassays results revealed that both essential oils exhibited insecticidal activities similar to the synthetic pyrethroid insecticide deltamethrin. Furthermore, oil dosage increments proportionately decreased the growth rate and reduced the losses in bean weight caused by cowpea weevils, and offspring emergence was almost abolished when parents were exposed to the LD₂₀ of each essential oil. Finally, significant oviposition impairments were perceived only in couples where females were exposed (i.e., females exposed and exposed couples) to the LD₂₀ of cinnamon and clove essential oils. Thus, by exhibiting similar insecticidal activities as synthetic insecticides and by significantly affecting the oviposition of sublethally exposed C. maculatus females, the cinnamon and clove essential oils represent valuable tools with potential of integration into the management of C. maculatus infestations.

Insectivorous Birds Are Attracted by Plant Traits Induced by Insect Egg Deposition

Insectivorous birds feed upon all developmental stages of herbivorous insects, including insect eggs if larvae and adults are unavailable. Insect egg deposition on plants can induce plant traits that are subsequently exploited by egg parasitoids searching for hosts. However, it is unknown whether avian predators can also use egg-induced plant changes for prey localization. Here, we studied whether great tits (Parus major) and blue tits (Cyanistes caeruleus) are attracted by traits of the Scots pine (Pinus sylvestris) induced by pine sawfly (Diprion pini) egg deposition. We chose this plant - insect system because sawfly egg deposition on pine needles is known to locally and systemically induce a change in pine volatile organic compounds (VOCs), and tits are known to prey upon sawfly eggs. In dual choice laboratory experiments, we simultaneously offered the birds an egg-free control branch and a systemically egg-induced branch. Significantly more birds visited the egg-induced branch first. We confirmed by GC-MS analyses that systemically egg-induced branches released more (E)-β-farnesene compared to control branches. Spectrophotometric analyses showed that control branches reflected more light than egg-induced branches throughout the avian visual range. Although a discrimination threshold model for blue tits suggests that the birds are poor at discriminating this visual difference, the role of visual stimuli in attracting the birds to egg-induced pines cannot be discounted. Our study shows, for the first time, that egg-induced odorous and/or visual plant traits can help birds to locate insect eggs without smelling or seeing those eggs.

Nonsensical choices? Fall armyworm moths choose seemingly best or worst hosts for their larvae, but neonate larvae make their own choices

Selecting optimal host plants is critical for herbivorous insects, such as fall armyworm (Spodoptera frugiperda), an important maize pest in the Americas and Africa. Fall armyworm larvae are presumed to have limited mobility, hence female moths are presumed to be largely responsible for selecting hosts. We addressed host selection by fall armyworm moths and neonate and older (3^rd-instar) larvae, as mediated by resistance and herbivory in maize plants. Thus, we compared discrimination among three maize cultivars with varying degrees of resistance to fall armyworm, and between plants subjected or not to two types of herbivory. The cultivars were: (i) susceptible, and deficient in jasmonic acid (JA) production and green leaf volatiles (GLV) emissions (inbred line B73-lox10); (ii) modestly resistant (B73), and; (iii) highly resistant (Mp708). The herbivory types were: (i) ongoing (= fall armyworm larvae present), and; (ii) future (= fall armyworm eggs present). In choice tests, moths laid more eggs on the highly resistant cultivar, and least on the susceptible cultivar, though on those cultivars larvae performed poorest and best, respectively. In the context of herbivory, moths laid more eggs: (i) on plants subject to versus free of future herbivory, regardless of whether plants were deficient or not in JA and GLV production; (ii) on plants subject versus free of ongoing herbivory, and; (iii) on plants not deficient in compared to deficient in JA and GLV production. Neonate larvae dispersed aerially from host plants (i.e. ballooned), and most larvae colonized the modestly resistant cultivar, and fewest the highly resistant cultivar, suggesting quasi-directional, directed aerial descent. Finally, dispersing older larvae did not discriminate among the three maize cultivars, nor between maize plants and (plastic) model maize plants, suggesting random, visually-oriented dispersal. Our results were used to assemble a model of host selection by fall armyworm moths and larvae, including recommendations for future research.

Plant Secondary Metabolites Modulate Insect Behavior-Steps Toward Addiction?

Plants produce a diversity of secondary metabolites (PSMs) that serve as defense compounds against herbivores and microorganisms. In addition, some PSMs attract animals for pollination and seed dispersal. In case of pollinating insects, PSMs with colors or terpenoids with fragrant odors attract pollinators in the first place, but when they arrive at a flower, they are rewarded with nectar, so that the pollinators do not feed on flowers. In order to be effective as defense chemicals, PSMs evolved as bioactive substances, that can interfere with a large number of molecular targets in cells, tissues and organs of animals or of microbes. The known functions of PSMs are summarized in this review. A number of PSMs evolved as agonists or antagonists of neuronal signal transduction. Many of these PSMs are alkaloids. Several of them share structural similarities to neurotransmitters. Evidence for neuroactive and psychoactive PSMs in animals will be reviewed. Some of the neuroactive PSMs can cause addiction in humans and other vertrebrates. Why should a defense compound be addictive and thus attract more herbivores? Some insects are food specialists that can feed on plants that are normally toxic to other herbivores. These specialists can tolerate the toxins and many are stored in the insect body as acquired defense chemicals against predators. A special case are pyrrolizidine alkaloids (PAs) that are neurotoxic and mutagenic in vertebrates. PAs are actively sequestered by moths of the family Arctiidae and a few other groups of arthropods. In arctiids, PAs are not only used for defense, but also serve as morphogens for the induction of male coremata and as precursors for male pheromones. Caterpillars even feed on filter paper impregnated with pure PAs (that modulate serotonin receptors in vertebrates and maybe even in insects) and thus show of behavior with has similarities to addiction in vertebrates. Not only PA specialists, but also many monophagous herbivores select their host plants according to chemical cues i.e., PSMs) and crave for plants with a particular PSMs, again a similarity to addiction in vertebrates.

Undetected Infection by Maize Bushy Stunt Phytoplasma Enhances Host-Plant Preference to Dalbulus maidis (Hemiptera: Cicadellidae)

Vector-borne plant pathogenic bacteria can induce changes in infected plants favoring the insect vector behavior and biology. The study aimed to determine the effect of maize bushy stunt phytoplasma (MBSP) postinoculation period on the host plant preference and transmission efficiency by the corn leafhopper, Dalbulus maidis DeLong & Wolcott, 1923 (Hemiptera: Cicadellidae). In a series of choice tests, D. maidis preference was measured as settling and oviposition on healthy maize plants versus infected maize plants showing early disease symptoms, advanced symptoms, or no symptoms. Finally, transmission efficiency of D. maidis was measured when the vector previously acquired the phytoplasma from asymptomatic source plants at different postinoculation periods. D. maidis adults preferred to settle and to oviposit on healthy than on symptomatic infected plants with advanced disease symptoms, and preferred asymptomatic plants over symptomatic ones. MBSP transmission by D. maidis was positively correlated with the postinoculation period of the source plant. Results suggest an MBSP modulation for D. maidis preference on asymptomatic infected maize plants in the early stages of the crop, allowing the pathogen an undetected transmission.

A Bird in the Hand Versus Two in the Bush? The Specialist Leafhopper Dalbulus maidis (Hemiptera: Cicadellidae) Does Not Discriminate Against Sub-optimal Host Plants (Zea spp.)

The corn leafhopper [Dalbulus maidis (DeLong & Wolcott)] is a specialist on Zea (Poaceae) that coevolved with maize (Zea mays mays) and its teosinte (Zea spp.) relatives. This study tested the hypothesis that host acceptance by females varies among Zea hosts, and is correlated with variation in defensive levels across those hosts. Prior studies revealed differences in plant defenses among Zea hosts and corresponding differences in corn leafhopper performance. Thus, host acceptance was expected to be correlated with defensive levels and offspring performance across Zea hosts, following the hypothesis that offspring performance mediates host preference. In parallel, host acceptance was expected to be correlated with transitions in life history strategy (perennial to annual life cycle), domestication status (wild to domesticated), and breeding intensity (landrace to hybrid variety) in Zea because variation in defensive levels and corn leafhopper performance were shown in prior studies to be correlated with those transitions. The study's hypotheses were tested by comparing, under no-choice conditions, host acceptance by corn leafhopper of a suite of Zea hosts encompassing those transitions: perennial teosinte (Zea diploperennis), Balsas teosinte (Zea mays parviglumis), and landrace and commercial hybrid maize. The results did not show differences in host acceptance for oviposition or feeding among the hosts. Thus, under no-choice conditions, all Zea hosts may be similarly acceptable for feeding and oviposition, despite marked ovipositional preferences under choice conditions and poorer offspring performance on teosintes relative to maize shown previously. The results suggested also that oviposition frequency per plant by females was not correlated with their offspring's performance.

Evolutionary dynamics of interactions between plants and their enemies: comparison of herbivorous insects and pathogens

Plants colonized land over 400 million years ago. Shortly thereafter, organisms began to consume terrestrial plant tissue as a nutritional resource. Most plant enemies are plant pathogens or herbivores, and they impose natural selection for plants to evolve defenses. These traits generate selection pressures on enemies. Coevolution between terrestrial plants and their enemies is an important element of the evolutionary history of both groups. However, coevolutionary studies of plant-pathogen interactions have tended to focus on different research topics than plant-herbivore interactions. Specifically, studies of plant-pathogen interactions often adopt a "gene-for-gene" conceptual framework. In contrast, studies of plants and herbivores often investigate escalation or elaboration of plant defense and herbivore adaptations to overcome it. The main exceptions to the general pattern are studies that focus on small, sessile herbivores that share many features with plant pathogens, studies that incorporate both herbivores and pathogens into a single investigation, and studies that test aspects of Thompson's geographic mosaic theory for coevolution. We discuss the implications of these findings for future research.

Forest litter crickets prefer higher substrate moisture for oviposition: Evidence from field and lab experiments

For insects, choosing a favorable oviposition site is a type of parental care, as far as it increases the fitness of its offspring. Niche theory predicts that crickets should show a bell-shaped oviposition response to substrate moisture. However, lab experiments with mole crickets showed a linear oviposition response to substrate moisture. Studies with the house cricket Acheta domesticus also showed a linear juvenile body growth response to water availability, thus adult ovipositing females should respond positively to substrate moisture. We used a field experiment to evaluate the relationship between oviposition preference and substrate moisture in forest litter-dwelling cricket species. We also evaluated oviposition responses to substrate moisture level in Ubiquepuella telytokous, the most abundant litter cricket species in our study area, using a laboratory study. We offered cotton substrate for oviposition which varied in substrate moisture level from zero (i.e., dry) to maximum water absorption capacity. We used two complementary metrics to evaluate oviposition preference: (i) presence or absence of eggs in each sampling unit as binary response variable, and (ii) number of eggs oviposited per sampling unit as count response variable. To test for non-linear responses, we adjusted generalized additive models (GAMM) with mixed effects. We found that both cricket oviposition probability and effort (i.e., number of eggs laid) increased linearly with substrate moisture in the field experiment, and for U. telytokous in the lab experiment. We discarded any non-linear responses. Our results demonstrate the importance of substrate moisture as an ecological niche dimension for litter crickets. This work bolsters knowledge of litter cricket life history association with moisture, and suggests that litter crickets may be particularly threatened by changes in climate that favor habitat drying.

Plant response to butterfly eggs: inducibility, severity and success of egg-killing leaf necrosis depends on plant genotype and egg clustering

Plants employ various defences killing the insect attacker in an early stage. Oviposition by cabbage white butterflies (Pieris spp.) on brassicaceous plants, including Brassica nigra, induces a hypersensitive response (HR) - like leaf necrosis promoting desiccation of eggs. To gain a deeper insight into the arms race between butterflies and plants, we conducted field and greenhouse experiments using different B. nigra genotypes. We investigated variation in HR and consequent survival of P. brassicae egg clusters. Impact of egg density, distribution type and humidity on HR formation and egg survival was tested. HR differed among plant genotypes as well as plant individuals. Egg density per plant did not affect HR formation. Remarkably, egg survival did not depend on the formation of HR, unless butterflies were forced to lay single eggs. Larval hatching success from single eggs was lower on plants expressing HR. This may be due to increased vulnerability of single eggs to low humidity conditions at necrotic leaf sites. We conclude that effectiveness of HR-like necrosis in B. nigra varies with plant genotype, plant individual and the type of egg laying behaviour (singly or clustered). By clustering eggs, cabbage white butterflies can escape the egg-killing, direct plant defence trait.

Floral Volatiles from Vigna unguiculata Are Olfactory and Gustatory Stimulants for Oviposition by the Bean Pod Borer Moth Maruca vitrata

We investigated the role of floral odors from cowpea, Vigna unguiculata (L.), in mediating oviposition of the bean pod borer moth, Maruca vitrata, a serious pest of grain legumes that flies to host plants at the flowering stage and oviposits onto flowers and buds. The flower of the host plant V. unguiculata was a stimulus for egg-laying by M. vitrata in an oviposition bioassay. Commercial longifolene, β-caryophyllene, linalool, geraniol, and (Z)-3-hexenyl acetate were used as stimulus. Each one elicited dose-dependent electroantennogram responses in female M. vitrata, and all but longifolene stimulated oviposition, when presented singly. Beta-caryophyllene was the most active stimulant, similar to that of the flower of V. unguiculata, and eliciting a dose-dependent oviposition response. Either olfaction or gustation was sufficient to mediate an oviposition response to V. unguiculata floral volatiles: intact M. vitrata responded to β-caryophyllene whether or not they could contact the source of the volatiles, and females with amputated antennae responded if allowed to contact the source. We believe this is the first demonstration in a moth where β-caryophyllene from the host plant was able to mediate an oviposition response. As β-caryophyllene is widely expressed by non-host plants, we suggest that its role in stimulating oviposition could be exploited as part of a push–pull strategy for pest management in which β-caryophyllene-expressing non-host plants provide a population sink for M. vitrata.

Foraging behaviour of an egg parasitoid exploiting plant volatiles induced by pentatomids: the role of adaxial and abaxial leaf surfaces

Several phases of herbivorous insect attack including feeding and oviposition are known to induce plant defenses. Plants emit volatiles induced by herbivores to recruit insect parasitoids as an indirect defense strategy. So far, volatiles induced by herbivore walking and their putative role in the foraging behavior of egg parasitoids have not been investigated. In this paper we studied the response of the egg parasitoid Trissolcus basalis toward volatiles emitted by Vicia faba plants as consequence of the walking activity of the host Nezara viridula. Olfactometer bioassays were carried out to evaluate wasp responses to plants in which the abaxial or the adaxial surfaces were subjected to walking or/and oviposition. Results showed that host female walking on the abaxial but not on the adaxial surface caused a repellence effect in T. basalis 24 h after plant treatment. The emission of active volatiles also occurred when the leaf was turned upside-down, indicating a specificity of stress localization. This specificity was supported by the results, which showed that oviposition combined with feeding elicit the induction of plant volatiles, attracting the parasitoid, when the attack occurred on the abaxial surface. Analyses of plant volatile blends showed significant differences between the treatments.

Natal origin affects host preference and larval performance relationships in a tritrophic system

Many insects face the challenge to select oviposition sites in heterogeneous environments where biotic and abiotic factors can change over time. One way to deal with this complexity is to use sensory experiences made during developmental stages to locate similar habitats or hosts in which larval development can be maximized. While various studies have investigated oviposition preference and larval performance relationships in insects, they have largely overlooked that sensory experiences made during the larval stage can affect such relationships. We addressed this issue by determining the role of natal experience on oviposition preference and larval performance relationships in a tritrophic system consisting of Galerucella sagittariae, feeding on the two host plants Potentilla palustris and Lysimachia thyrsiflora, and its larval parasitoid Asecodes lucens. We firstly determined whether differences in host‐derived olfactory information could lead to divergent host selection, and secondly, whether host preference could result in higher larval performance based on the natal origin of the insects. Our results showed that the natal origin and the quality of the current host are both important aspects in oviposition preference and larval performance relationships. While we found a positive relationship between preference and performance for natal Lysimachia beetles, natal Potentilla larvae showed no such relationship and developed better on L. thyrsiflora. Additionally, the host selection by the parasitoid was mainly affected by the natal origin, while its performance was higher on Lysimachia larvae. With this study, we showed that the relationship between oviposition preference and larval performance depends on the interplay between the natal origin of the female and the quality of the current host. However, without incorporating the full tritrophic context of these interactions, their implication in insect fitness and potential adaptation cannot be fully understood.

Herbivore Damage and Prior Egg Deposition on Host Plants Influence the Oviposition of the Generalist Moth Trichoplusia ni (Lepidoptera: Noctuidae)

Female insects have the difficult task of locating host plants that maximize the survival and success of their offspring. In this study, the oviposition preferences of the cabbage looper moth, Trichoplusia ni (Hübner), for soybean plants, Glycine max (L.), under various treatments-undamaged, mechanically damaged, damaged by T. ni or Spodoptera frugiperda (Smith) larvae or by Bemisia tabaci (Gennadius) adults, egg-free plants, and plants previously oviposited by conspecific or heterospecific females (S. frugiperda)-were investigated using two-choice tests. Additionally, the volatile compounds emitted by the plants under the different treatments were identified by gas chromatography-mass spectrometry. Our results showed that females showed no preferences for undamaged or mechanically damaged plants. However, they oviposited more often on undamaged plants than on those previously damaged by T. ni, S. frugiperda, or B. tabaci. In contrast, females preferred to oviposit on plants previously oviposited by conspecific and heterospecific females than on egg-free plants. Plants damaged by conspecific or heterospecific larvae emitted methyl salicylate, indole, and octyl butyrate, compounds not released by undamaged or mechanically damaged plants. Whitefly damage induced the release of higher quantities of Z(3)-hexenyl acetate, (R)-(+)-limonene, and (E)-β-ocimene compared to plants damaged by larvae and suppressed the emission of linalool. Egg deposition by conspecific and heterospecific moths induced the emission of (R)-(+)-limonene, octyl butyrate, and geranyl acetone but suppressed the release of linalool. This study showed that a generalist moth species can discriminate between plants of different quality, and suggests that females use volatile compounds as cues during this process.

The influence of volatile semiochemicals from stink bug eggs and oviposition-damaged plants on the foraging behaviour of the egg parasitoid Telenomus podisi

During host selection, physical and chemical stimuli provide important cues that modify search behaviours of natural enemies. We evaluated the influence of volatiles released by eggs and egg extracts of the stink bug Euschistus heros and by soybean plants treated with the eggs and egg extracts on Telenomus podisi foraging behaviour. Responses to volatiles were evaluated in Y-tube olfactometers after exposure to (1) one egg cluster for 24 h; (2) plants with eggs laid by the stink bug, tested at 24, 48, and 72 h after treatment; (3) plants with eggs laid artificially, tested at 24, 48, and 72 h after treatment; and (4) plants treated with acetone or hexane extracts of eggs. Telenomus podisi was attracted to volatiles emitted by one egg cluster and to acetone extracts of one egg cluster, but not to air or acetone controls. There were no responses to odours of plants treated with eggs or egg extracts. Analysis of acetone extracts of egg clusters by gas chromatography revealed the major components were saturated and unsaturated fatty acids, including hexadecanoic acid, linoleic acid, and (Z)-9-octadecenoic acid. Our results suggest that one egg cluster and the acetone extract of one egg cluster contain volatile compounds that can modify T. podisi foraging behaviour, and that the amounts of these compounds, probably together with some minor compounds, are important for host recognition by T. podisi. Also, the oviposition damage or egg extracts on the plant did not elicit indirect defences that attracted Telenomus podisi.

Caterpillar mimicry by plant galls as a visual defense against herbivores

Plant galls, induced by arthropods and various other organisms have an intimate relationship with host plants, and gall-inducers have limited mobility. In addition to their own photosynthesis, galls are resource sinks rich with nutrients, with neighboring plant organs commonly serving as external photosynthate sources. Galls, if not well defended, may therefore be attractive food sources for herbivores. Galls produced by some aphids, jumping plant lice, thrips, and gall midges in Japan, Palearctic region and in the Middle East visually resemble lepidopteran caterpillars. I propose that such visual resemblance may reduce herbivory of galls and surrounding plant tissues, resulting in an increase in galler survival due to reduced gall damage and in enhanced galler growth due to improved nutrient inflow to the galls, when herbivores avoid colonizing or consuming plant parts that look as if they have been occupied by other herbivores. Potential predators and parasitoids of caterpillars may be attracted to the caterpillar-like galls and then attack real caterpillars and other invertebrate herbivores, which would also be beneficial for both gallers and their hosts.

Resisting the onset of herbivore attack: plants perceive and respond to insect eggs

Plants can respond to attack by herbivorous insects very soon after herbivores start producing a new generation by depositing eggs onto their leaves. Egg-induced plant responses may result in killing the attacker in its egg stage. However, if the eggs do survive, they can also prime feeding-induced plant defenses against the larvae hatching from eggs. In this paper we focus first on egg-induced plant responses that resemble hypersensitive responses (HR) to phytopathogens and lead to egg desiccation or detachment from plants. We then summarize the current knowledge about egg-mediated effects on feeding-induced plant defenses against larvae. Finally, we discuss the insect species specificity of plant responses to eggs and the variability of insect susceptibility to these responses.

Oviposition by mutualistic seed-consuming pollinators reduces fruit abortion in a recently discovered pollination mutualism

A prerequisite for the evolutionary stability of pollinating seed-consuming mutualisms is that each partner benefits from the association. However, few studies of such mutualism have considered the benefit gained by the pollinators. Here, we determined how the pollinating seed-predators ensure the provisioning of their offspring in the recently discovered mutualism between Rheum nobile and Bradysia flies. The correlation between flower fate and fly oviposition was examined. Floral traits and patterns of variation in fruit abortion and fly oviposition were investigated to determine whether female flies exhibit preferences for particular flowers when laying eggs. Indole-3-acetic acid (IAA) was quantified to determine whether female flies manipulate host physiology. Flowers that flies oviposited on had a significantly lower probability of fruit abortion compared with intact flowers. Females did not exhibit oviposition preference for any of the floral traits examined. There was no significant correlation between fruit abortion and fly oviposition in terms of either flower position or timing of flowering. IAA concentrations in oviposited flowers were significantly higher than in intact flowers. Our results suggest that oviposition by the mutualistic seed-consuming pollinator Bradysia sp., greatly reduces the probability of fruit abortion of its host, R. nobile; this may be attributed to the manipulation of host physiology through regulating IAA levels.

Priming of anti-herbivore defence in Nicotiana attenuata by insect oviposition: herbivore-specific effects

Oviposition by Spodoptera exigua on Nicotiana attenuata primes plant defence against its larvae that consequently suffer reduced performance. To reveal whether this is a general response of tobacco to insect oviposition or species-specific, we investigated whether also Manduca sexta oviposition primes N. attenuata's anti-herbivore defence. The plant response to M. sexta and S. exigua oviposition overlapped in the egg-primed feeding-induced production of the phenylpropanoid caffeoylputrescine. While M. sexta larvae were unaffected in their performance, they showed a novel response to the oviposition-mediated plant changes: a reduced antimicrobial activity in their haemolymph. In a cross-resistance experiment, S. exigua larvae suffered reduced performance on M. sexta-oviposited plants like they did on S. exigua-oviposited plants. The M. sexta oviposition-mediated plant effects on the S. exigua larval performance and on M. sexta larval immunity required expression of the NaMyb8 transcription factor that is governing biosynthesis of phenylpropanoids such as caffeoylputrescine. Thus, NaMyb8-dependent defence traits mediate the effects that oviposition by both lepidopteran species exerts on the plant's anti-herbivore defence. These results suggest that oviposition by lepidopteran species on N. attenuata leaves may generally prime the feeding-induced production of certain plant defence compounds but that different herbivore species show different susceptibility to egg-primed plant effects.

Elm leaves 'warned' by insect egg deposition reduce survival of hatching larvae by a shift in their quantitative leaf metabolite pattern

Plants may take insect eggs on their leaves as a warning of future herbivory and intensify their defence against feeding larvae. Responsible agents are, however, largely unknown, and little knowledge is available on this phenomenon in perennial plants. We investigated how egg deposition affects the anti-herbivore defence of elm against the multivoltine elm leaf beetle. Prior egg deposition caused changes in the quality of feeding-damaged leaves that resulted in increased larval mortality and reduced reproductive capacity of the herbivore by harming especially female larvae. Chemical analyses of primary and secondary leaf metabolites in feeding-damaged, egg-free (F) and feeding-damaged, egg-deposited (EF)-leaves revealed only small differences in concentrations when comparing metabolites singly. However, a pattern-focused analysis showed clearly separable patterns of (F) and (EF)-leaves because of concentration differences in especially nitrogen and phenolics, of which robinin was consumed in greater amounts by larvae on (EF) than on (F)-leaves. Our study shows that insect egg deposition mediates a shift in the quantitative nutritional pattern of feeding-damaged leaves, and thus might limit the herbivore's population growth by reducing the number of especially female herbivores. This may be a strategy that pays off in a long run particularly in perennial plants against multivoltine herbivores.