Daily age, growth rate, and pelagic larval duration of commercially important snapper species in Abrolhos National Marine Park

The age and daily growth of fish are registered through the deposition of increments in their otoliths, which are concretions formed by the precipitation of substances present in the endolymphatic fluid, mainly calcium carbonate (CaCO3). Faced with the need to fill some of the gaps in the knowledge on the occurrence and duration of the initial stages of snapper species' life cycles in the Abrolhos Bank, this study aimed to describe the growth rates, age, and period of pelagic larval duration (PLD) of three snapper species during the larval pre-settlement phase, in the Abrolhos Bank region. The post-larvae were captured using light traps. Otoliths were removed from 117 samples of snapper species; however, only 69 were viable for age estimation, of which 15 were Lutjanus analis, 25 were Lutjanus jocu, and 29 were Lutjanus synagris. Together, the samples presented individuals with total lengths ranging from 16.14 to 24.76 mm and ages from 21 to 39 days. Settlement marks were found for all three species, and the average PLD was ~25 days. The somatic growth of the snapper species was positively correlated with otolith growth. L. jocu presented the greatest daily growth compared to the other species. The three species use the Abrolhos Bank as a larval settlement site, demonstrating plasticity by using different habitats throughout their lives.

Maternal Effects and Trophodynamics Drive Interannual Larval Growth Variability of Atlantic Bluefin Tuna (Thunnus thynnus) from the Gulf of Mexico

Two cohorts of Atlantic bluefin tuna (Thunnus thynnus) larvae were sampled in 2017 and 2018 during the peak of spawning in the Gulf of Mexico (GOM). We examined environmental variables, daily growth, otolith biometry and stable isotopes and found that the GOM18 cohort grew at faster rates, with larger and wider otoliths. Inter and intra-population analyses (deficient vs. optimal growth groups) were carried out for pre- and post-flexion developmental stages to determine maternal and trophodynamic influences on larval growth variability based on larval isotopic signatures, trophic niche sizes and their overlaps. For the pre-flexion stages in both years, the optimal growth groups had significantly lower δ15N, implying a direct relationship between growth potential and maternal inheritance. Optimal growth groups and stages for both years showed lower C:N ratios, reflecting a greater energy investment in growth. The results of this study illustrate the interannual transgenerational trophic plasticity of a spawning stock and its linkages to growth potential of their offsprings in the GOM.

Less is more: partial larvicidal efficacy of plant leachate leads to larger Aedes aegypti mosquitoes

Major efforts to control the population of Aedes aegypti mosquitoes involve the use of synthetic insecticides, which can be harmful to the environment. Most plant compounds are eco-friendly and some of them have biocontrol potential, whereas a fraction of these compounds is released into the environment through the leaf-leaching process. We evaluated the effects of secondary compounds from Ateleia glazioviana and Eucalyptus grandis senescent leaf leachates on Ae. aegypti larval mortality, adult emergence time, and wing size using a microcosm approach. The microcosms consisted of 10 larvae kept in water (control) and under four treatments with leachates from a combination of plant species and leaching time (7 or 14 days). Chemical analyses of the leachates showed the presence of carboxaldehyde and Heptatriocotanol, which have antimicrobial properties, potentially reducing the food available for larvae. β-Sitosterol, Stigmasterol, α-Amyrin, and Lupeol are compounds with inhibitory, neurotoxic, and larvicidal effects. Both plant species' leachates increased larval mortality and decreased emergence time due to the presence of compounds toxic to the larvae. Larger organisms emerged in treatments with 7-days leachates, likely due to the high concentration of dissolved organic matter in the leachates. The higher mortality in 7-days leachates may also increase the organic matter from co-specific decomposition, improving adult size. Therefore, if the mosquito population is not locally extinct, compounds present in leaf leachates may act as a resource enhancing larvae growth, potentially increasing survivors' fitness. In conclusion, biocontrol attempts using urban green spaces may have unexpected outcomes, such as resulting in larger pest organisms.

Body condition of larval roundherring, Gilchristella aestuaria (family Clupeidae), in relation to harmful algal blooms in a warm-temperate estuary

Eutrophication-driven harmful algal blooms (HABs) can have secondary effects on larval fishes that rely on estuaries as nurseries. However, few studies worldwide have quantified these effects despite the global rise in eutrophication. This study presents a novel approach using biochemical body condition analyses to evaluate the impact of HABs on the growth and body condition of the larvae of an estuarine resident fish. Recurrent phytoplankton blooms of Heterosigma akashiwo occur in the warm-temperate Sundays Estuary on the southeast coast of South Africa. The response in body condition and assemblage structure on larval estuarine roundherring (Gilchristella aestuaria) was measured in conjunction with bloom conditions, water quality and zooplanktonic prey and predators. Larvae and early juveniles were sampled during varying intensity levels, duration and frequency of hypereutrophic blooms. This study demonstrated that extensive HABs could significantly impact larval roundherring, G. aestuaria, by decreasing larval nutritional condition and limiting their growth, resulting in poor grow-out into the juvenile phase. Poor condition and growth may likely affect recruitment success to adult populations, and since G. aestuaria is an important forage fish and zooplanktivore, poor recruitment will hold consequences for estuarine food webs.

Dimmed gene knockout shortens larval growth and reduces silk yield in the silkworm, Bombyx mori

The bHLH domain transcription factor, Bombyx mori-derived dimmed (Bmdimm), is directly regulated by the JH-BmMet/BmSRC-BmKr-h1 pathway and plays a key role in regulating the expression of FibH, which codes the main component of silk protein. However, the other roles of Bmdimm in silk protein synthesis remain unclear. Here, we established a Bmdimm knockout (KO) line containing a 7-bp deletion via CRISPR/Cas9 system, which led to the absence of the bHLH domain. The expression level of silk protein genes and silk yield decreased significantly in the Bmdimm KO line. Moreover, knocking out Bmdimm led to shortened larval stages and significant weight loss in larvae and adults. Bmdimm was found to be highly expressed in the silk gland, but it was also expressed in the fat body. The expression level of Bmkr-h1 in the fat body was significantly downregulated in the Bmdimm KO line. Exogenous JHA treatment upregulated Bmkr-h1 and rescued the phenotype of larval growth in the Bmdimm KO line. In conclusion, knocking out Bmdimm led to a shortened larval stage via the inhibition of Bmkr-h1 expression, then reduced silk yield. These findings help to elucidate the regulatory mechanism of fibroin synthesis and larval development in silkworms.

Effects of Polystyrene Diet on the Growth and Development of Tenebrio molitor

In recent years, the role of Tenebrio molitor in degrading polystyrene foam through its gut microbes has become the focus of research. However, little literature has reported the effect of feeding on polystyrene foam on the growth and development of Tenebrio molitor. In this study, we investigated the impacts of different polystyrene by evaluating the vital signs of Tenebrio molitor fed in the intestines and excrement fluids using RNA-Seq t.echnology and then verifying the transcriptome sequencing findings using qRT-PCR technology. The average weight of Tenebrio molitor larvae in the wheat bran group increased significantly. Tenebrio molitor larvae in the PS group, on the other hand, didn't grow as much and had a much lower average weight than those in the wheat bran group. Compared to the bran group, the excrement of Tenebrio molitor fed only on polystyrene foam was flaky and coarse, increased nitrogen and phosphorus atomic concentration ratios by about 50%, decreased potassium atomic concentration ratios by 63%, with the enterocytes and circular muscle of Tenebrio molitor falling as well. Kyoto Encyclopedia of Genes and Genomes enrichment indicated that the differential genes were mainly related to metabolic pathways. There was an agreement between qRT-PCR and RNA-Seq analyses for the growth and development genes chitinase, heat shock protein 70, and cytochrome P450. Only feeding polystyrene foam shall lead to the growth and development retardation of Tenebrio molitor.

Zerynthia polyxena Locally Monophagous on Aristolochia pallida in the Susa Valley

In insect-plant biology, oviposition choices and larval development on different host plants are crucial factors to be investigated. To design conservation strategies for protected Lepidoptera, which are overall oligophagous but locally monophagous, it is important to understand which host plant species is locally preferred. We thus investigated oviposition choices and larval development of the protected butterfly Zerynthia polyxena in controlled laboratory conditions, using three possible host plant species which are present in the Piedmont region: Aristolochia pallida, A. clematitis, and A. rotunda. We found that laboratory conditions are not favorable for Z. polyxena oviposition, even if the fertility of the females was in normal range for Papilionidae. However, we were able to understand the local monophagy of the species on A. pallida in the Susa Valley through larval survival and development stages. Egg hatching was similar among the three host plant species; however, even if larvae eat and grow similarly on the different host plant species until the third larval stage, the only larvae that reached the pupal stage were those fed with A. pallida. In conclusion, whereas Z. polyxena is oligophagous in the rest of Europe for the genus Aristolochia, the species is locally monophagous on A. pallida in the Susa Valley.

Insecticidal Effect of Phosphine on Eggs of the Khapra Beetle (Coleoptera: Dermestidae)

Trogoderma granarium Everts (Coleoptera: Dermestidae) is one of the most important quarantine pests of stored grains. Control of this insect species can be achieved through a gaseous insecticide, phosphine. Many studies focus on the effect of phosphine on different developmental stages of insects, with most of them highlighting eggs as the most tolerant stage. Our data showed that 2-d-old eggs of T. granarium are more susceptible than 1-d-old eggs. Faster hatching was observed in eggs exposed to phosphine for 2 d compared to controls and the result was more pronounced for 1-d-old than 2-d-old eggs. In contrast to the 2-d exposure, hatching rates of eggs exposed to 4 and 6 d were notably reduced, while there was a delay in egg hatching compared to controls. Moreover, larval development from untreated eggs was faster than the larvae from treated eggs, regardless of the exposure time. These dissimilar patters in larval growth may suggest certain delayed effects of phosphine fumigation. The results of the present work can be further utilized for the development of phosphine-based quarantine and pre-shipment treatments for the control of T. granarium.

RNAi of vacuolar-type H+-ATPase genes causes growth delay and molting defect in Henosepilachna vigintioctopunctata

Henosepilachna vigintioctopunctata is one of the most serious insect pests to a large number of nightshades and cucurbits. RNA interference (RNAi) triggered by double-stranded RNA (dsRNA) offers a reduced risk approach to control the beetle. Identification of amenable target genes and determination of appropriate life stage for dsRNA treatment are two critical steps in order to improve RNAi efficiency. In the present paper, we identified three vATPase genes, namely HvvATPaseC, HvvATPaseE and HvvATPaseH. We found that the three transcripts were widely expressed in the eggs, first- to fourth-instar larvae, prepupae, pupae and adults. They were abundantly transcribed in the hindgut and Malpighian tubules, in contrast to the epidermis and fat body. Three days' ingestion of dsvATPaseC, dsvATPaseE and dsvATPaseH by the fourth-instar larvae significantly decreased corresponding transcript level by 90.1, 88.9 and 97.2%, greatly reduced larval fresh weight by 28.0, 29.9 and 28.0%, and caused 66.7, 100 and 78.7% larval lethality respectively. Comparably, 3 days' exposure of the third-instar larvae to dsvATPaseC significantly reduced HvvATPaseC mRNA level by 89.5%, decreased approximately 80% of the larval fresh weight, and killed 100% of the treated larvae. Therefore, the three vATPase genes, especially HvvATPaseE, are potential amenable target genes and young larvae are more susceptible to dsRNA. Our findings will enable the development of the dsRNA-based pesticide to control H. vigintioctopunctata.

Lunar rhythms in growth of larval fish

Growth and survival of larval fishes is highly variable and unpredictable. Our limited understanding of this variation constrains our ability to forecast population dynamics and effectively manage fisheries. Here we show that daily growth rates of a coral reef fish (the sixbar wrasse, Thalassoma hardwicke) are strongly lunar-periodic and predicted by the timing of nocturnal brightness: growth was maximized when the first half of the night was dark and the second half of the night was bright. Cloud cover that obscured moonlight facilitated a 'natural experiment', and confirmed the effect of moonlight on growth. We suggest that lunar-periodic growth may be attributable to light-mediated suppression of diel vertical migrations of predators and prey. Accounting for such effects will improve our capacity to predict the future dynamics of marine populations, especially in response to climate-driven changes in nocturnal cloud cover and intensification of artificial light, which could lead to population declines by reducing larval survival and growth.

Development of Tenebrio molitor (Coleoptera: Tenebrionidae) on Poultry Litter-Based Diets: Effect on Chemical Composition of Larvae

In order to investigate a low-cost and sustainable food source, the present study evaluated the use of poultry litter for rearing Tenebrio molitor Linnaeus, 1758 (Coleoptera:  Tenebrionidae). The experiment was performed with five diets containing increasing levels of poultry litter (0, 25, 50, 75, and 100%) replacing the control diet and five replicates with 50 larvae per sample unit. Larval growth and development were evaluated and the chemical compositions of diet and T. molitor larvae were determined. Larval development and reproduction efficiency of T. molitor were similar in all treatments. The sole use of poultry litter to feed T. molitor reduced the crude protein of flour by only 8%. Including 50% or more poultry litter in the standard diet is the best-suited formulation for larvae production and incorporation of minerals in the larvae. Mealworm can be grown successfully on diets composed by poultry litter, the diet did not affect survival, growth, and development; however, studies spanning several insect generations should be performed to determine the effects of diet composition on adult fecundity. The knowledge acquired using poultry litter to feed T. molitor will be useful to carry out new research, in addition to evidencing the possibility of low-cost mass rearing of these larvae.

Individual and combined impacts of sulfoxaflor and Nosema bombi on bumblebee (Bombus terrestris) larval growth

Sulfoxaflor is a globally important novel insecticide that can have negative impacts on the reproductive output of bumblebee (Bombus terrestris) colonies. However, it remains unclear as to which life-history stage is critically affected by exposure. One hypothesis is that sulfoxaflor exposure early in the colony's life cycle can impair larval development, reducing the number of workers produced and ultimately lowering colony reproductive output. Here we assess the influence of sulfoxaflor exposure on bumblebee larval mortality and growth both when tested in insolation and when in combination with the common fungal parasite Nosema bombi, following a pre-registered design. We found no significant impact of sulfoxaflor (5 ppb) or N. bombi exposure (50 000 spores) on larval mortality when tested in isolation but found an additive, negative effect when larvae received both stressors in combination. Individually, sulfoxaflor and N. bombi exposure each impaired larval growth, although the impact of combined exposure fell significantly short of the predicted sum of the individual effects (i.e. they interacted antagonistically). Ultimately, our results suggest that colony-level consequences of sulfoxaflor exposure for bumblebees may be mediated through direct effects on larvae. As sulfoxaflor is licensed for use globally, our findings highlight the need to understand how novel insecticides impact non-target insects at various stages of their development.

Evolution of reduced minimum critical size as a response to selection for rapid pre-adult development in Drosophila melanogaster

Adult body size in holometabolus insects is directly proportional to the time spent during the larval period. The larval duration can be divided into two parts: (i) pre-critical duration-time required to attain a critical size/critical weight that would result in successful completion of development and metamorphosis even under non-availability of nutrition beyond the time of attainment of critical size, and (ii) post-critical duration-the time duration from the attainment of critical size till pupation. It is of interest to decipher the relative contribution of the two larval growth phases (from the hatching of the egg to the attainment of critical size, and from the attainment of critical size to pupation) to the final adult size. Many studies using Drosophila melanogaster have shown that selecting populations for faster development results in the emergence of small adults. Some of these studies have indirectly reported the evolution of smaller critical size. Using two kinds of D. melanogaster populations, one of which is selected for faster/accelerated pre-adult development and the other their ancestral control, we demonstrate that the final adult size is determined by the time spent as larvae post the attainment of critical size despite having increased growth rate during the second larval instar. Our populations under selection for faster pre-adult development are exhibiting adaptive bailout due to intrinsic food limitation as against extrinsic food limitation in the yellow dung fly.

Estimating the Age of Forensically Useful Blowfly, Sarconesia chlorogaster (Diptera: Calliphoridae), Using Larval Length and Weight

Determining the age of an insect collected in a corpse is a key element to estimate the minimum postmortem interval in forensic entomology. Along with models of accumulated degree-hours, the estimation of the age based on larval weight and length is among the most common methods for this purpose. Sarconesia chlorogaster (Wiedemann, 1830), along with other Calliphoridae, is an important species in forensics in South America. However, studies analyzing the weight and length of S. chlorogaster larvae during development have not yet been done. In this work, we develop growth models based on the weight and length of larvae in different temperatures and provide formulas that can be used to estimate the age of the larvae based on the weight and length for each temperature. Larvae were reared at six temperatures (10, 15, 20, 25, 30, 35°C), and the measurements of larval length and weight were taken during all development until they stopped feeding. For the measurements, we attempted to use methodologies that can be easily replicated and do not require equipment that could be of difficult access. The results of this work come to complement and improve the use of S. chlorogaster in forensic applications.

Rearing Theretra oldenlandiae (Lepidoptera: Sphingidae) Larvae on an Artificial Diet

The hawk moth Theretra oldenlandiae (Fabricius) is an important insect pest because in the larval stage it feeds on agricultural crops and ornamental plants such as the eddoe and garden balsam. In this study, we established methods for rearing T. oldenlandiae in the laboratory using an artificial diet containing dry powder of a wild grass Cayratia japonica (Thunb.) Gagnep. Several artificial diets were tested with different ratios of a commercial diet, Insecta LFM, and the dry leaf powder, and including different antibiotics, and the composition of the standard diet on which larvae performed best was determined. The standard diet contains 20 g of Insecta LFM, 4 g of leaf powder, 100 ml of water, 75 mg of chloramphenicol, and 200 μl of propionic acid. Larvae reared on the standard diet became larger pupae than those reared on C. japonica leaves. This result suggests that the larvae have growth potential that is masked on C. japonica leaves, and that C. japonica may not be the most suitable host species for T. oldenlandiae larvae in terms of nutrient level.

Moonlight enhances growth in larval fish

Moonlight mediates trophic interactions and shapes the evolution of life-history strategies for nocturnal organisms. Reproductive cycles and important life-history transitions for many marine organisms coincide with moon phases, but few studies consider the effects of moonlight on pelagic larvae at sea. We evaluated effects of moonlight on growth of pelagic larvae of a temperate reef fish using "master chronologies" of larval growth constructed from age-independent daily increment widths recorded in otoliths of 321 individuals. We found that daily growth rates of fish larvae were enhanced by lunar illumination after controlling for the positive influence of temperature and the negative influence of cloud cover. Collectively, these results indicate that moonlight enhances growth rates of larval fish. This pattern is likely the result of moonlight's combined effects on foraging efficiency and suppression of diel migrations of mesopelagic predators, and has the potential to drive evolution of marine life histories.

The Histone Demethylase KDM5 Is Essential for Larval Growth in Drosophila

Regulated gene expression is necessary for developmental and homeostatic processes. The KDM5 family of transcriptional regulators are histone H3 lysine 4 demethylases that can function through both demethylase-dependent and -independent mechanisms. While loss and overexpression of KDM5 proteins are linked to intellectual disability and cancer, respectively, their normal developmental functions remain less characterized. Drosophila melanogaster provides an ideal system to investigate KDM5 function, as it encodes a single ortholog in contrast to the four paralogs found in mammalian cells. To examine the consequences of complete loss of KDM5, we generated a null allele of Drosophila kdm5, also known as little imaginal discs (lid), and show that it is essential for viability. Animals lacking KDM5 show a dramatically delayed larval development that coincides with decreased proliferation and increased cell death in wing imaginal discs. Interestingly, this developmental delay is independent of the well-characterized Jumonji C (JmjC) domain-encoded histone demethylase activity of KDM5, suggesting key functions for less characterized domains. Consistent with the phenotypes observed, transcriptome analyses of kdm5 null mutant wing imaginal discs revealed the dysregulation of genes involved in several cellular processes, including cell cycle progression and DNA repair. Together, our analyses reveal KDM5 as a key regulator of larval growth and offer an invaluable tool for defining the biological activities of KDM5 family proteins.

Nutrient-Dependent Impact of Microbes on Drosophila suzukii Development

Drosophila suzukii Matsumura is an invasive species of vinegar fly that has become a prominent pest of berries and other soft-skinned fruits. Unlike most other Drosophila species, female D. suzukii flies lay their eggs in ripening and ripe fruits and larvae develop within the fruit. To understand how D. suzukii larvae utilize ripe and ripening fruits, which usually have low levels of protein, we investigated the microbiota of field-captured and laboratory-reared D. suzukii flies and further examined the combined influence of diet and microbes on host fitness. Field-captured flies were associated with diverse microbiota, which varied significantly with sampling location and season. In contrast, laboratory-reared flies possessed strikingly lower bacterial abundance and diversity. A comparison of conventionally reared (CR) and germ-free (GF) flies revealed that the microbiota of D. suzukii does not alter its development significantly but decreases its life span under conditions of a nutrient-sufficient diet. However, the microbiota is essential for D. suzukii development on strawberry-based or blueberry-based fruit diets. This developmental failure could be rescued by reassociation with single bacterial or fungal species or by the addition of a high quantity of heat-killed microbes. In addition, we found that proteins are limiting with respect to fly development on fruit-based diets and that GF flies show signs of protein starvation. Taken together, our study results demonstrate that the microbiota provides key proteins required for the development of D. suzukii reared on fresh fruit. Our work shows that the impact of microbes on fly fitness depends strongly on nutritional conditions.

Animals are commonly associated with specific microbes, which play important roles in host development and fitness. However, little information about the function of microbes has been available for the important invasive pest Drosophila suzukii, also known as Spotted wing drosophila. Our study results demonstrate that the abundance and structure of microbiota in D. suzukii are strongly affected by the environment, where microbes have variable roles depending on the nutritional situation. For instance, we found that the presence of microbes is deleterious for flies growing on a protein-rich diet and yet is beneficial for flies growing on a diet of protein-poor fruits. Additionally, germ-free flies must feed on microbes to obtain the necessary protein for larval development on strawberries and blueberries. Our report validates the complexity seen in host-microbe interactions and may provide information useful for D. suzukii pest control.

Knockdown of ATPsyn-b caused larval growth defect and male infertility in Drosophila

The ATPsyn-b encoding for subunit b of ATP synthase in Drosophila melanogaster is proposed to act in ATP synthesis and phagocytosis, and has been identified as one of the sperm proteins in both Drosophila and mammals. At present, its details of functions in animal growth and spermatogenesis have not been reported. In this study, we knocked down ATPsyn-b using Drosophila lines expressing inducible hairpin RNAi constructs and Gal4 drivers. Ubiquitous knockdown of ATPsyn-b resulted in growth defects in larval stage as the larvae did not grow bigger than the size of normal second-instar larvae. Knockdown in testes did not interrupt the developmental excursion to viable adult flies, however, these male adults were sterile. Analyses of testes revealed disrupted nuclear bundles during spermatogenesis and abnormal shaping in spermatid elongation. There were no mature sperm in the seminal vesicle of ATPsyn-b knockdown male testes. These findings suggest us that ATPsyn-b acts in growth and male fertility of Drosophila.

Life history of the Glanville fritillary butterfly in fragmented versus continuous landscapes

Habitat loss and fragmentation threaten the long-term viability of innumerable species of plants and animals. At the same time, habitat fragmentation may impose strong natural selection and lead to evolution of life histories with possible consequences for demographic dynamics. The Baltic populations of the Glanville fritillary butterfly (Melitaea cinxia) inhabit regions with highly fragmented habitat (networks of small dry meadows) as well as regions with extensive continuous habitat (calcareous alvar grasslands). Here, we report the results of common garden studies on butterflies originating from two highly fragmented landscapes (FL) in Finland and Sweden and from two continuous landscapes (CL) in Sweden and Estonia, conducted in a large outdoor cage (32 by 26 m) and in the laboratory. We investigated a comprehensive set of 51 life-history traits, including measures of larval growth and development, flight performance, and adult reproductive behavior. Seventeen of the 51 traits showed a significant difference between fragmented versus CL. Most notably, the growth rate of postdiapause larvae and several measures of flight capacity, including flight metabolic rate, were higher in butterflies from fragmented than CL. Females from CL had shorter intervals between consecutive egg clutches and somewhat higher life-time egg production, but shorter longevity, than females from FL. These results are likely to reflect the constant opportunities for oviposition in females living in continuous habitats, while the more dispersive females from FL allocate more resources to dispersal capacity at the cost of egg maturation rate. This study supports theoretical predictions about small population sizes and high rate of population turnover in fragmented habitats selecting for increased rate of dispersal, but the results also indicate that many other life-history traits apart from dispersal are affected by the degree of habitat fragmentation.

Sorghum seed maturity affects the weight and feeding duration of immature corn earworm, Helicoverpa zea, and fall armyworm, Spodoptera frugiperda, in the laboratory

Corn earworm, Helicoverpa zea Boddie (Lepidoptera: Noctuidae), and fall armyworm, Spodoptera frugiperda J.E. Smith, are occasional pests in sorghum, Sorghum bicolor L. Moench (Poales: Poaceae), and can be economically damaging when conditions are favorable. Despite the frequent occurrence of mixed-species infestations, the quantitative data necessary for developing yield loss relationships for S. frugiperda are not available. Although these species share similar biological characteristics, it is unknown whether their damage potentials in developing grain sorghum panicles are the same. Using no-choice feeding assays in the laboratory, this study examined larval growth and feeding duration for H. zea and S. frugiperda in the absence of competition. Each species responded positively when exposed to sorghum seed in the soft-dough stage, supporting evidence for the interactions between host-quality and larval growth and development. The results of this study also confirmed the suitability of using laboratory-reared H. zea to develop sorghum yield loss estimates in the field, and provided insights into the biological responses of S. frugiperda feeding on developing sorghum seed.