Sex pheromones of rice moth,Corcyra cephalonica Stainton : I. Identification of male pheromone

Chemically-mediated colonization of black cherry by the peach bark beetle, Phloeotribus liminaris

The peach bark beetle (Phloeotribus liminaris Harris, PBB) affects the health, quality, and value of black cherry (Prunus serotina Ehrh.) within the Central Hardwoods Forest Region of North America. When colonized by adult beetles, black cherry trees produce a defensive exudate, or 'gum', staining the wood and decreasing its value up to 90%. Current management tactics are inadequate to avoid extensive damage to most veneer-sized black cherry in the region. We test the hypothesis that PBB colonization behavior is chemically-mediated and determine the extent to which PBB is attracted to compounds associated with wounded or PBB-infested cherry wood. Through olfactometer and field bioassays, we determined that adult PBB were attracted to cherry branches infested with female beetles. We then used dynamic headspace sampling to collect volatiles associated with wounded and infested bolts of black cherry. The volatile benzaldehyde dominated these collections and was more abundant in aerations of female-infested bolts than other odor sources. In subsequent field bioassays, we evaluated the bioactivity of benzaldehyde, as well as α-longipinene, in combination with several chemical carriers. Traps baited with benzaldehyde captured more PBB than all other treatments, irrespective of other lure components. Moreover, PBB were not attracted to traps baited solely with ethanol, a common attractant for bark beetles that colonize hardwood trees. This is the first report of benzaldehyde as an attractant for a species of bark beetle and could aid in developing semiochemical-based management tactics for this important pest.

Juvenile hormone pathway in honey bee larvae: A source of possible signal molecules for the reproductive behavior of Varroa destructor

The parasitic mite Varroa destructor devastates honey bee (Apis mellifera) colonies around the world. Entering a brood cell shortly before capping, the Varroa mother feeds on the honey bee larvae. The hormones 20-hydroxyecdysone (20E) and juvenile hormone (JH), acquired from the host, have been considered to play a key role in initiating Varroa's reproductive cycle. This study focuses on differential expression of the genes involved in the biosynthesis of JH and ecdysone at six time points during the first 30 hr after cell capping in both drone and worker larvae of A. mellifera. This time frame, covering the conclusion of the honey bee brood cell invasion and the start of Varroa's ovogenesis, is critical to the successful initiation of a reproductive cycle. Our findings support a later activation of the ecdysteroid cascade in honey bee drones compared to worker larvae, which could account for the increased egg production of Varroa in A. mellifera drone cells. The JH pathway was generally downregulated confirming its activity is antagonistic to the ecdysteroid pathway during the larva development. Nevertheless, the genes involved in JH synthesis revealed an increased expression in drones. The upregulation of jhamt gene involved in methyl farnesoate (MF) synthesis came into attention since the MF is not only a precursor of JH but it is also an insect pheromone in its own right as well as JH-like hormone in Acari. This could indicate a possible kairomone effect of MF for attracting the mites into the drone brood cells, along with its potential involvement in ovogenesis after the cell capping, stimulating Varroa's initiation of egg laying.

Sexual communication in castniid moths: Males mark their territories and appear to bear all chemical burden

Castniid moths (Lepidoptera: Castniidae) display a butterfly-like reproductive behavior, i.e., they use visual stimuli for mate location and females have apparently lost their pheromone glands in an evolutionary context. In this paper we report for the first time the identification of three new compounds, namely n-octadecyl acetate, (Z)-9-octadecenyl acetate and (E,Z)-2,13-octadecadienyl acetate, in males of the Castniid Palm Borer, Paysandisia archon, which could be involved in its short-range courtship behavior, and also shed light on recent controversies on the sexual behavior of the species. The compounds are produced in a ring-shaped gland of the male terminalia and have occasionally been detected in very minor amounts (ng) in ovipositor extracts of females, but only while mating or just after copulation. We also report that males use the already known (E,Z)-2,13-octadecadienol to mark their territory by rubbing their midlegs against the upper side of nearby leaves, especially palm leaves. This compound, produced in large amounts, is mostly concentrated in the midleg basitarsi and its maximum production is detected on the sexually mature 1-day-old specimens. In addition, analysis of male wings extracts confirms the presence of Z,E and E,E-farnesals, which are mostly produced in the median band of hindwings of 48-53 h-old insects. The biological significance of farnesals in this species is unknown. Our results point out that the chemical communication of P. archon relies mostly on males, which appear to bear all chemical burden in this respect.

Sexual communication in day-flying Lepidoptera with special reference to castniids or 'butterfly-moths'

Butterflies and moths are subject to different evolutionary pressures that affect several aspects of their behaviour and physiology, particularly sexual communication. Butterflies are day-flying insects (excluding hedylids) whose partner-finding strategy is mainly based on visual cues and female butterflies having apparently lost the typical sex pheromone glands. Moths, in contrast, are mostly night-flyers and use female-released long-range pheromones for partner-finding. However, some moth families are exclusively day-flyers, and therefore subject to evolutionary pressures similar to those endured by butterflies. Among them, the Castniidae, also called 'butterfly-moths' or 'sun-moths', behave like butterflies and, thus, castniid females appear to have also lost their pheromone glands, an unparallel attribute in the world of moths. In this paper, we review the sexual communication strategy in day-flying Lepidoptera, mainly butterflies (superfamily Papilionoidea), Zygaenidae and Castniidae moths, and compare their mating behaviour with that of moth families of nocturnal habits, paying particular attention to the recently discovered butterfly-like partner-finding strategy of castniids and the fascinating facts and debates that led to its discovery.

Circadian release of male-specific components of the greater date moth, Aphomia (Arenipses) sabella, using sequential SPME/GC/MS analysis

The greater date moth (GDM), Aphomia sabella Hampson (Lepidoptera: Pyralidae: Galleriinae), is a serious pest of date palms, Phoenix dactylifera. The release of volatiles from both males and females was investigated using sequential SPME/GC/MS analysis. Males release a complex mixture of compounds in a circadian rhythm during the night between 03:00 and 05:00 hr. Six compounds were identified: benzaldehyde, sulcatol (6-methyl-5-hepten-2-ol), geranyl acetone [(E)-6,10-dimethyl-5,9-undecadien-2-one], phenylacetaldehyde, 2-phenylpropenal, and (R)-fuscumol [(R)-(E)-6, 10-dimethyl-5, 9-undecadien-2-ol]. Benzaldehyde, sulcatol, and geranyl acetone were found only in trace amounts. These compounds were in glands located in the forewing of males only. Small amounts of acetoin and 2,3-butanediol were found sporadically in the SPME/GC/MS analyses of volatiles from females, and these compounds probably originate from microorganisms. This is the first finding of a circadian release of male-specific compounds in moths. GC/EAD analyses with synthetic standards of compounds released by males showed that the female antenna is stimulated by all six compounds, while the male antenna responded only to phenylacetaldehyde. A possible pheromonal role for the male-specific compounds is suggested by the circadian rhythm of their release and the EAD response of females to them. However, trapping tests with the main male-specific compounds in screen cages in the laboratory or in the field did not reveal any significant behavioral responses from females or males. Copulation in the laboratory was observed only in the presence of date palm tissue, thus suggesting that sexual communication and mating of GDM moths probably occurs in the crown of date palms.

Sex pheromones of rice moth,Corcyra cephalonica Stainton : II. Identification and role of female pheromone

Laboratory investigations of mating behavior in the rice moth,Corcyra cephalonica Stainton (Lepidoptera: Pyralidae; Galleriinae) showed that male moths are attracted at short range to live, virgin female moths and to female abdominal-tip extract. Volatiles collected from virgin female moths contained one component eliciting an electroantennographic (EAG) response from the male moth, and the chemical, spectroscopic, and Chromatographic data on this component were consistent with that of synthetic 6,10,14-tri-methyl-2-pentadecanol. This compound caused an EAG response from the male moth and attracted male moths in the bioassay. The pheromone is thought to play a role in courtship, and the synthetic material was shown to cause the male moths to search for a mate and attempt copulation.

Females of the bumblebee parasite, Aphomia sociella, excite males using a courtship pheromone

Aphomia sociella (Lepidoptera: Pyralidae: Galleriinae) is a parasitic moth of bumblebees. Behavioral experiments show that A. sociella females emit semiochemicals that influence male pre-mating behavior and serve as a courtship pheromone. GC/EAD and two-dimensional GC/MS (GCxGC-TOFMS) analyses of extracts of females revealed three antennally active compounds. Comparative GC and GCxGC-TOFMS analyses of extracts and synthetic standards confirmed the identity of the antennally active compounds as hexan-1-ol (1), 6,10,14-trimethylpentadecan-2-one (2), and 6,10,14-trimethylpentadecan-2-ol (3). In laboratory bioassays, alcohol 3 and, at higher doses, ketone 2 initiated male courtship behavior associated with ultrasonic production. Hexan-1-ol (1) and ketone 2 enhanced the activity of alcohol 3. These data suggest that hexan-1-ol, 6,10,14-trimethylpentadecan-2-ol, and 6,10,14-trimethylpentadecan-2-one constitute the female-produced courtship pheromone of A. sociella.

Moths behaving like butterflies. Evolutionary loss of long range attractant pheromones in castniid moths: a Paysandisia archon model

Background

In the course of evolution butterflies and moths developed two different reproductive behaviors. Whereas butterflies rely on visual stimuli for mate location, moths use the ‘female calling plus male seduction’ system, in which females release long-range sex pheromones to attract conspecific males. There are few exceptions from this pattern but in all cases known female moths possess sex pheromone glands which apparently have been lost in female butterflies. In the day-flying moth family Castniidae (“butterfly-moths”), which includes some important crop pests, no pheromones have been found so far.

Methodology/Principal Findings

Using a multidisciplinary approach we described the steps involved in the courtship of P. archon, showing that visual cues are the only ones used for mate location; showed that the morphology and fine structure of the antennae of this moth are strikingly similar to those of butterflies, with male sensilla apparently not suited to detect female-released long range pheromones; showed that its females lack pheromone-producing glands, and identified three compounds as putative male sex pheromone (MSP) components of P. archon, released from the proximal halves of male forewings and hindwings.

Conclusions/Significance

This study provides evidence for the first time in Lepidoptera that females of a moth do not produce any pheromone to attract males, and that mate location is achieved only visually by patrolling males, which may release a pheromone at short distance, putatively a mixture of Z,E-farnesal, E,E-farnesal, and (E,Z)-2,13-octadecadienol. The outlined behavior, long thought to be unique to butterflies, is likely to be widespread in Castniidae implying a novel, unparalleled butterfly-like reproductive behavior in moths. This will also have practical implications in applied entomology since it signifies that the monitoring/control of castniid pests should not be based on the use of female-produced pheromones, as it is usually done in many moths.

Male moth songs tempt females to accept mating: the role of acoustic and pheromonal communication in the reproductive behaviour of Aphomia sociella

BACKGROUND

Members of the subfamily Galleriinae have adapted to different selective environmental pressures by devising a unique mating process. Galleriinae males initiate mating by attracting females with either chemical or acoustic signals (or a combination of both modalities). Six compounds considered candidates for the sex pheromone have recently been identified in the wing gland extracts of Aphomia sociella males. Prior to the present study, acoustic communication had not been investigated. Signals mediating female attraction were likewise unknown.

METHODOLOGY/PRINCIPAL FINDINGS

Observations of A. sociella mating behaviour and recordings of male acoustic signals confirmed that males initiate the mating process. During calling behaviour (stationary wing fanning and pheromone release), males disperse pheromone from their wing glands. When a female approaches, males cease calling and begin to produce ultrasonic songs as part of the courtship behaviour. Replaying of recorded courting songs to virgin females and a comparison of the mating efficiency of intact males with males lacking tegullae proved that male ultrasonic signals stimulate females to accept mating. Greenhouse experiments with isolated pheromone glands confirmed that the male sex pheromone mediates long-range female attraction.

CONCLUSION/SIGNIFICANCE

Female attraction in A. sociella is chemically mediated, but ultrasonic communication is also employed during courtship. Male ultrasonic songs stimulate female sexual display and significantly affect mating efficiency. Considerable inter-individual differences in song structure exist. These could play a role in female mate selection provided that the female's ear is able to discern them. The A. sociella mating strategy described above is unique within the subfamily Galleriinae.

Composition and electrophysiological activity of constituents identified in male wing gland secretion of the bumblebee parasite Aphomia sociella

Male wing gland secretion and volatiles emanating from calling males were investigated in the bumble bee wax moth, Aphomia. sociella, using comprehensive two-dimensional gas chromatography-mass spectrometry (GCxGC-TOF-MS), gas chromatography-infrared spectroscopy (GC-FTIR), enantioselective gas chromatography, electroantennography (EAG), gas chromatography with electroantennographic detection (GC-EAD), and NMR. GC-EAD analysis of the male wing gland secretion revealed seven active areas, corresponding to 1-hexanol (1), 2-phenylethanol (2), [(R),(Z)]-nona-2,6-dien-4-olide (3), [(S),(Z)]-nona-6-en-4-olide (4), mellein (5), phytone (6), and a mixture of C(18) fatty acids (7). Solid-phase microextraction (SPME) confirmed the presence of 2-phenylethanol, nona-2,6-dien-4-olide, nona-6-en-4-olide, mellein, and phytone in volatiles emanating from a calling male. Though the abundance of these compounds slightly differed in SPME and gland secretion analysis, nona-2,6-dien-4-olide and mellein dominated in both samples, followed by 2-phenylethanol, nona-6-en-4-olide, and phytone. The strong antennal responses elicited by components of the secretion suggest that one or more of these compounds constitute the sex pheromone. Both sexes perceived male wing gland secretion, with females being significantly more sensitive compared to males.

Homofarnesals: female sex attractant pheromone components of the southern cowpea weevil, Callosobruchus chinensis

The southern cowpea weevil, Callosobruchus chinensis (Coleoptera: Bruchidae), is a major pest of stored legumes in warm temperate and tropical climates. The female sex attractant pheromone was extracted from filter-paper shelters taken from containers that housed virgin females. The extracts were purified by various chromatographic techniques, and the biologically active components in the fractions were screened by gas chromatographic-electroantennographic detection analysis with male antennae. Two compounds that elicited electrophysiological responses were isolated, and gas chromatography-mass spectrometry, nuclear magnetic resonance, and micro-chemical analyses suggested that the active compounds were homofarnesals, (2Z,6E)- and (2E,6E)-7-ethyl-3,11-dimethyl-2,6,10-dodecatrienals. Males of C. chinensis were significantly attracted to filter paper discs loaded with the synthetic compounds at 0.01-0.1 ng compared to solvent control in a Y-tube olfactometer assay. These pheromone components represent unique chemical structures within the genus Callosobruchus.