Pheromone Blend Research Articles

Variations on a Theme: Two Structural Motifs Create Species-Specific Pheromone Channels for Multiple Species of South American Cerambycid Beetles.

We describe the identification, synthesis, and field-testing of aggregation-sex pheromones, or likely pheromone candidates, of seven species of South American cerambycid beetles in the subfamily Cerambycinae, of the tribes Eburiini and Neoibidionini. Analyses of extracts of volatiles released by adult males revealed that Eburodacrys dubitata White produce 11-methyltridecanal, whereas the males of Eburodacrys assimilis Gounelle, Eburodacrys flexuosa Gounelle, and Eburodacrys lenkoi Napp and Martins produce blends of this compound, along with its analog 10-methyldodecanal. In contrast, males of Compsibidion graphicum (Thomson) and Compsibidion sommeri (Thomson) produce blends of 10-methyldodecanal and its corresponding alcohol 10-methyldodecanol. The results from field bioassays with synthetic compounds showed that each species was specifically attracted to traps containing their reconstructed pheromone blend. However, E. assimilis was not trapped, possibly due to inhibition by non-natural enantiomers in the racemic test compounds. During the trials for the Compsibidion species, adults of another cerambycid species, Tetraopidion mucoriferum (Thomson), were captured in significant numbers in traps baited with 10-methyldodecanol, suggesting that this compound is a pheromone component for this species. This study demonstrates another case of conservation of pheromone structures within South American cerambycid species. It also highlights how blends of closely related structures, differing only in chain length or functional group, make the evolution of species-specific pheromone channels possible.

Practical Synthesis and Field Application of the Synthetic Sex Pheromone of Rice Stem Borer, Chilo suppressalis (Lepidoptera: Pyralidae)

Rice stem borer, Chilo suppressalis, is a common and major serious pest of rice, maize, and wheat crops across Asia, Europe, and Oceania countries. Its sex pheromone consists of three analogously compounds, i.e., (Z)-hexadec-11-enal (1), (Z)-octadec-13-enal (2), and (Z)-hexadec-9-enal (3), as long-chain aliphatic internal cis-alkenyl aldehydes. In order to perform an economic and widespread pest control management of rice stem borer, a versatile and efficient synthetic strategy is required. A versatile and efficient synthesis using a common synthetic route for cis-alkenals with high overall yields is described. Commercially available inexpensive aliphatic diols were chosen as starting materials. Two key steps were employed to synthesize the long-chain aliphatic internal cis-alkenes in excellent yields, including the alkylation of terminal alkynes without the utilization of a highly polar aprotic cosolvent and the versatile cis-selective semihydrogenation for the reduction of internal alkynes with excellent stereoselectivity. The results of field tests showed that the synthetic sex pheromone blend was highly effective for the capture of rice stem borer.

Factors Affecting Disruption of Navel Orangeworm (Lepidoptera: Pyralidae) Using Aerosol Dispensers.

Mating disruption is used to help manage the navel orangeworm on approximately 200,000 ha of tree nut crops. Aerosol dispensers are the most common formulation, and all formulations use an incomplete pheromone blend consisting solely of (Z11,Z13)-hexadecadienal. Profile analysis (examination of capture and males in pheromone traps as a function of spatial density of dispensers) demonstrated a sharp drop of males captured with a very low density of dispensers, and then an approximately linear relationship between 90 and approaching 100% suppression. This near-linear portion of the profile includes both dispenser densities in which crop protection has been demonstrated, and densities in which it is unlikely. Suppression of males in pheromone traps was lost the next night after dispensers were removed, suggesting that the active ingredient was not persistent in the orchard environment. During most of the summer preharvest period, turning the dispensers off 1 or 2 h before the end of the predawn period of sexual activity provides the same amount of suppression of sexual communication as emission throughout the period of sexual activity. This suggests that encountering the pheromone from the mating disruption dispensers had a persistent effect on males. During the autumn postharvest period, only emission prior to midnight suppressed communication on nights on which the temperature fell below 19°C by midnight. These findings and the analysis will help manufacturers refine their offerings for mating disruption for this important California pest, and buyers of mating disruption to assess cost-effectiveness of competing offerings.

Distinct Roles of Cuticular Aldehydes as Pheromonal Cues in Two Cotesia Parasitoids.

Cuticular compounds (CCs) that cover the surface of insects primarily serve as protection against entomopathogens, harmful substances, and desiccation. However, CCs may also have secondary signaling functions. By studying the role of CCs in intraspecific interactions, we may advance our understanding of the evolution of pheromonal communication in insects. We previously found that the gregarious parasitoid, Cotesia glomerata (L.), uses heptanal as a repellent pheromone to help avoid mate competition among sibling males, whereas another cuticular aldehyde, nonanal, is part of the female-produced attractive sex pheromone. Here, we show that the same aldehydes have different pheromonal functions in a related solitary parasitoid, Cotesia marginiventris (Cresson). Heptanal enhances the attractiveness of the female's sex pheromone, whereas nonanal does not affect a female's attractiveness. Hence, these common aldehydes are differentially used by the two Cotesia species to mediate, synergistically, the attractiveness of the main constituents of their respective sex pheromones. The specificity of the complete sex pheromone blend is apparently regulated by two specific, less volatile compounds, which evoke strong electroantennographic (EAG) responses. This is the first demonstration that volatile CCs have evolved distinct pheromonal functions to aid divergent mating strategies in closely related species. We discuss the possibility that additional compounds are involved in attraction and that, like the aldehydes, they are likely oxidative products of unsaturated cuticular hydrocarbons.

Early-exposure to new sex pheromone blends alters mate preference in female butterflies and in their offspring

While the diversity of sex pheromone communication systems across insects is well documented, the mechanisms that lead to such diversity are not well understood. Sex pheromones constitute a species-specific system of sexual communication that reinforces interspecific reproductive isolation. When odor blends evolve, the efficacy of male-female communication becomes compromised, unless preference for novel blends also evolves. We explore odor learning as a possible mechanism leading to changes in sex pheromone preferences in the butterfly Bicyclus anynana. Our experiments reveal mating patterns suggesting that mating bias for new blends can develop following a short learning experience, and that this maternal experience impacts the mating outcome of offspring without further exposure. We propose that odor learning can be a key factor in the evolution of sex pheromone blend recognition and in chemosensory speciation.

Response of fall armyworm, Spodoptera frugiperda (J. E. Smith) to different pheromone blends under Indian environmental conditions

Fall armyworm (FAW), Spodoptera frugiperda (J. E. Smith) is a pest of maize native to America that invaded India recently in 2018. Field and laboratory experiments were conducted in Bengaluru, India to find a suitable pheromone blend for trapping males of fall armyworm. The field evaluation studies showed that pheromone blend with Z-9-tetradecenyl acetate, Z-11-hexadecenyl acetate and Z-7-dodecenyl acetate in 87: 12.5 : 0.5 ratio attracted and trapped statistically significant number of male moths compared to other five blends using funnel traps. The laboratory evaluation of 6 different pheromone blends using Electroantennogram (EAG) with male antenna of S. frugiperda elicited statistically on par responses with each other. From the different dosage field study with optimum attracting blend, it was found that 2 mg loading trapped highest number of moths and was statistically on par with 3 mg pheromone lure. Further monitoring study carried out under farmer's field condition with 2 mg loading of pheromone blend with Z-9-tetradecenyl acetate, Z-11-hexadecenyl acetate and Z-7-dodecenyl acetate in 87: 12.5: 0.5 ratio found to be more effective in attracting and trapping male moths up to 60 days.

Synergism of Pheromone and Host-Plant Volatile Blends in the Attraction of Leucinodes orbonalis Guenee Males

Brinjal Fruit and shoot borer, Leucinodes orbonalis Guenee is considered to be the key insect pest that attacks brinjal plant. Insects such as L. orbonalis, which has extremely diverse adaptations such as hidden and protected lifestyles in the adult stage and concealed habits in the larval stage cannot be easily controlled with cover sprays of insecticides. Moreover, Pheromone-host plant odour interactions might also play a pivotal role in the evolution of mating communication and host-finding behaviour. The objective of the present work was to evaluate whether host plant volatiles synergise male L. orbonalis attraction to sex pheromone. Steam distillation method and super Q entrapment technique were used for the extraction of volatiles from brinjal plant leaves, shoots and fruits and sex pheromone from the insects respectively. Preliminary laboratory studies have shown that the male insects attracted to the host plant volatiles. Bioassay using Y-shaped olfactometer with different doses of the combination of sex pheromone and host plant volatiles were used to test the synergism. Two Whatman no. 1 filter papers (2.5 cm×2.5 cm) were used, one treated with a known amount of sex pheromone+host plant volatile and the other treated with equal amount of sex pheromone. In each experiment, the dose of sex pheromone was not changed and peak dose identified from the bioassay conducted previously was used. The dose of each host plant volatile was prepared by decreasing and increasing from the peak dose identified from the previous bioassays. Six doses of sex pheromone+fruit volatiles (25 μg+(8-48 mg)), sex pheromone+leaf volatile (25 μg+(12-42 mg)) and sex pheromone+shoot volatile (25 μg+(8-48 mg)) were tested using 15 male insects separately and each dose was replicated 5 times. The number of insects that moved into the sex pheromone+host plant volatile treated and sex pheromone treated arms within 5 minutes were recorded. This assay was carried out between 20.00–24.00 h and the test insects were not used repeatedly. Results revealed that all three types of volatiles from the host plant increased the attraction of male insects to the sex pheromone. In addition, the volatiles from brinjal fruits significantly increased the male attraction to the pheromone blend (p<0.05). The observed enhanced male attraction to the mixtures of pheromone and plant volatiles will facilitate the development of effective pest control programs for L. orbonalis. Keywords: Sex pheromone, Host plant volatiles, Synergism, Leucinodes orbonalis, Pest management

Ants Sense, and Follow, Trail Pheromones of Ant Community Members.

Ants deposit trail pheromones that guide nestmates to food sources. We tested the hypotheses that ant community members (Western carpenter ants, Camponotus modoc; black garden ants, Lasius niger; European fire ants, Myrmica rubra) (1) sense, and follow, each other’s trail pheromones, and (2) fail to recognize trail pheromones of allopatric ants (pavement ants, Tetramorium caespitum; desert harvester ants, Novomessor albisetosus; Argentine ants, Linepithema humilis). In gas chromatographic-electroantennographic detection analyses of a six-species synthetic trail pheromone blend (6-TPB), La. niger, Ca. modoc, and M. rubra sensed the trail pheromones of all community members and unexpectedly that of T. caespitum. Except for La. niger, all species did not recognize the trail pheromones of N. albisetosus and Li. humilis. In bioassays, La. niger workers followed the 6-TPB trail for longer distances than their own trail pheromone, indicating an additive effect of con- and hetero-specific pheromones on trail-following. Moreover, Ca. modoc workers followed the 6-TPB and their own trail pheromones for similar distances, indicating no adverse effects of heterospecific pheromones on trail-following. Our data show that ant community members eavesdrop on each other’s trail pheromones, and that multiple pheromones can be combined in a lure that guides multiple species of pest ants to lethal food baits.

Influence of host plant, geography and pheromone strain on genomic differentiation in sympatric populations of Ostrinia nubilalis.

Patterns of mating for the European corn borer (Ostrinia nubilalis) moth depend in part on variation in sex-pheromone blend. The ratio of (E)-11- and (Z)-11-tetradecenyl acetate (E11- and Z11-14:OAc) in the pheromone blend that females produce and males respond to differs between strains of O.nubilalis. Populations also vary in female oviposition preference for and larval performance on maize (C4) and nonmaize (C3) host plants. The relative contributions of sexual and ecological trait variation to the genetic structure of O.nubilalis remains unknown. Host-plant use (13 C/14 C ratios) and genetic differentiation were estimated among sympatric E and Z pheromone strain O.nubilalis males collected in sex-pheromone baited traps at 12 locations in Pennsylvania and New York between 2007 and 2010. Among genotypes at 65 single nucleotide polymorphism marker loci, variance at a position in the pheromone gland fatty acyl-reductase (pgfar) gene at the locus responsible for determining female pheromone ratio (Pher) explained 64% of the total genetic differentiation between males attracted to different pheromones (male response, Resp), providing evidence of sexual inter-selection at these unlinked loci. Principal coordinate, Bayesian clustering, and distance-based redundancy analysis (dbRDA) demonstrate that host plant history or geography does not significantly contribute to population variation or differentiation among males. In contrast, these analyses indicate that pheromone response and pgfar-defined strain contribute significantly to population genetic differentiation. This study suggests that behavioural divergence probably plays a larger role in driving genetic variation compared to host plant-defined ecological adaptation.

Effect of canopy cover on development of cedar (&lt;i&gt;Cedrela fissilis&lt;/i&gt;) and aspects of damage caused by &lt;i&gt;Hypsipyla grandella&lt;/i&gt; in agroforestry system

Cedrela fissilis (Vell.) is an important wood species, native to South America. It is appreciated for its physical characteristics and, therefore, its native specimens are overexploited.Commercial cultivation initiatives have been continuously flawed as a result of the damage caused by mahogany shoot borer Hypsipyla grandella (Zeller, 1848).Planting under shaded sites has been one of the management methods used to reduce insect attacks. However, the reason why mahogany shoot borer does not attack shaded plants as often is still unknown. Therefore, the aim of this research was to find cultivation parameters that could combine proper plant development and low rate ofattacks by Hypsipyla grandella.For this purpose, increases in height and shoot diameter of cedar seedlings, planted in agroforestry systems, were monitored for the two first years. Three canopy cover rates, namely, 0-20%, 20-40% and 40-60%, were tested for plant development andfrequency of attacks byHypsipyla grandella. The adult population of the insect was monitored with semiochemicals throughout the experimental period, and two pheromonal blends and one food bait were tested. Field results showed that one of the pheromone blends was efficient in identifying small variations in the population of adult specimens. Regarding to the plant development, the treatment with the highest cover rate showed the lowest parameters compared to the intermediate cover. The frequency of attacks byHypsipyla grandella was greater in the treatment with the lowest cover (0-20%).The results suggest that in canopy cover, ranging from 20 to 40%, good rates of initial development of plants can be combined with low frequency of attack by Hypsipyla grandella.

Two Sympatric Spodoptera Species Could Mutually Recognize Sex Pheromone Components for Behavioral Isolation.

Spodoptera exigua and S. litura are two sympatric species in China and many other countries. Both moths employ a multiple component sex pheromone blend, including a common component Z9,E12-14:OAc, and two specific components Z9-14:OH and Z11-16:OAc for S. exigua, and one specific component Z9,E11-14:OAc for S. litura. For the two species, it has been well documented that males are able to recognize and behaviorally attracted by their species-specific sex pheromone, which functions as a means of reproductive isolation, but whether males could mutually recognize pheromone components of its sympatric species is unknown. In the present study, the electroantennogram (EAG) and field evaluation were conducted to address this topic. The EAG recordings revealed that males of each species could significantly respond to specific components of its sympatric species, although the response values were lower than that to its own major component. In field tests, the specific components Z9-14:OH and Z11-16:OAc of S. exigua strongly inhibited the male catches of S. litura to its conspecific sex pheromone, while specific component Z9,E11-14:OAc of S. litura significantly reduced the male catches of S. exigua to its sex pheromone. Furthermore, the combined lure of the two species completely inhibited male catches of S. litura, and significantly decreased the male catches of S. exigua, compared to the species-specific lure alone. The results demonstrated that males of the two sibling species could perceive the specific components of its counterpart, suggesting that mutual recognition of pheromone components may function to strengthen the behavioral isolation between the two species. Our study has added new knowledge to the reproductive isolation via sex pheromone communication system in sympatric moth species, and provided a base for designing of mating disruption tactics targeting multispecies by using insect sex pheromones.

Two terpenoids activates close mating behavior and enhances trap efficiency of sex pheromone of Grapholita molesta

Grapholita molesta (Busck) (Lepidoptera: Tortricidae) is a notorious pest of many Rosaceae crops worldwide. Enhancement of trap efficiency of its sex pheromone was devised by addition of E-β-ocimene and E-β-farnesene. The addition of E-β-ocimene or E-β-farnesene to sex pheromone increased electroantennogram response of male G. molesta compared to sex pheromone alone. Blend of pheromone and E-β-ocimene or E-β-farnesene in 1:0.1 increased the upwind flight and landing behaviors. Furthermore, field experiments showed that sex lures with E-β-ocimene, or /and E-β-farnesene, enhanced trapping efficiency compared to sex pheromone alone. These results may provide the basis for the development of efficient pest management systems against G. molesta using plant volatiles and insect sex pheromones.

Pheromone-binding proteins based phylogenetics and phylogeography of Maruca spp. from Asia, Africa, Oceania, and South America.

Variations in the functional response of legume pod borer (Maruca vitrata) populations to sex pheromone blends were observed in Asia and Africa. Hence, this study was carried out to understand the differences in pheromone‐binding proteins (PBPs) among Maruca populations in Asia, Africa, Oceania, and South America. A de novo transcriptome assembly was adopted to sequence the entire transcribed mRNAs in M. vitrata from Taiwan. The raw‐sequence data were assembled using homologous genes from related organisms in GenBank to detect M. vitrata PBPs (MvitPBPs). Sections of the cDNA of MvitPBP of different length were used to design primers to amplify the full‐length cDNA of PBPs. All three PBP sequences comprised three exons interspersed by two introns. In total, 92 MvitPBP1 haplotypes, 77 MvitPBP2 haplotypes, and 64 MvitPBP3 haplotypes were identified in 105, 98, and 68 Maruca individuals, respectively. High pairwise F ST values (0.41–0.73) and phylogenetic analyses distinguished the putative Maruca species in South America from those occurring in rest of the world, and possibly two putative subspecies in Asia and Africa. The haplotype networks and Automatic Barcode Gap Discovery analyses also confirmed these results. The negative Tajima's D and Fu's F S values showed the recent demographic expansion of Maruca populations. Thus, this study confirmed the presence of different Maruca species and/or subspecies in different continents based on the diversity within PBP genes. Additional sampling and studies are suggested for Oceania and South America. The genetic differences among Maruca populations should be carefully considered while using sex pheromone lures and bio‐control agents.

Are Pheromones Key to Unlocking Cryptic Lizard Diversity?

Animals use mating traits to compete for, attract, and choose mates. Because mating traits influence mate choice, the divergence of mating traits between populations can result in reproductive isolation. This can occur without associated morphological divergence, producing reproductively isolated cryptic species that are visually indistinguishable. Thus, identifying the mating traits in morphologically conservative groups is key to resolving diversity and speciation processes. Lizards contain many such groups, with phylogeographic studies often revealing highly divergent but morphologically cryptic lineages within species. Considering that cryptic lizard species can be sympatric but morphologically indistinguishable, we hypothesize that candidate species will exhibit divergent pheromones and that pheromones will have typically diverged more than morphology. To test this, we used gas chromatography to characterize pheromones (epidermal pore secretions) from 10 genetically divergent lineages of the Bynoe's gecko (Heteronotia binoei) species complex in northern Australia. Multivariate analyses of pheromone blends and morphology indicate that pheromones are lineage specific and have diverged relatively more than morphology. Such specificity suggests that pheromones influence behavioral isolation in this morphologically conservative lizard radiation. These results suggest that pheromone data may unlock the tremendous cryptic diversity currently being uncovered in many lizard groups.

Racemic Pheromone Blends Disrupt Mate Location in the Invasive Swede Midge, Contarinia nasturtii.

Swede midge, Contarinia nasturtii Kieffer, is an invasive cecidomyiid pest that causes serious losses of Brassica oilseed and vegetable crops in the Northeastern U.S. and Canada. Currently, few alternatives to systemic insecticides exist for its management. Because a single feeding larva can render heading Brassica crops unmarketable, management strategies that prevent oviposition are needed urgently. Pheromone-mediated mating disruption is a promising management approach for swede midge because it prevents mating and subsequent crop damage. While the swede midge pheromone has been identified, one of the major barriers to using it in mating disruption is the high cost of synthesis. Racemic blends, consisting of natural and non-natural stereoisomers, could be useful for mating disruption because they are cheaper to produce. However, it is not clear whether racemic pheromone blends attract males and/or prevent them from locating and mating with females. Here, we studied the behavior of male swede midge in Y-tube and wind tunnel bioassays to pheromone blends. Specifically, we tested whether males: (1) are attracted to different doses of pheromone, (2) discriminate between blends comprising natural stereospecific or racemic components, or a combination thereof, and (3) are able to locate and copulate with females in pheromone-permeated olfactometers. We found that picogram amounts of pheromone attracted males and prevented them from locating females in y-tube olfactometers. While males were more attracted to stereospecific blends, compared to racemic blends, all blends tested prevented nearly all males mating with females. Therefore, low dose racemic blends may be promising for pheromone-mediated mating disruption.

The Role of Minor Pheromone Components in Segregating 14 Species of Longhorned Beetles (Coleoptera: Cerambycidae) of the Subfamily Cerambycinae.

We present research on the chemical ecology of 14 species of longhorned beetles (Coleoptera: Cerambycidae), in four tribes of the subfamily Cerambycinae, conducted in east-central Illinois over 8 yr. Adult males produce aggregation-sex pheromones that attract both sexes. Twenty independent field bioassays explored the pheromone chemistry of the species and tested the possible attractive or antagonistic effects of compounds that are not produced by a given species, but are pheromone components of other species. Analyses of beetle-produced volatiles revealed compounds that had not been reported previously from several of the species. The most common pheromone component was (R)-3-hydroxyhexan-2-one, but pheromones of some species included isomers of the related 2,3-hexanediols. Males of the congeners Phymatodes amoenus (Say) and Phymatodes testaceus (L.) produced pure (R)-2-methylbutan-1-ol. Enantiomers of 2-methylbutan-1-ol also proved to be powerful synergists for Megacyllene caryae (Gahan), Sarosesthes fulminans (F.), and Xylotrechus colonus (F.). The major components of pheromone blends were consistently present in collections of headspace volatiles from male beetles, and only the major components were inherently attractive to a subset of species when tested as single components. Minor components of some species acted as powerful synergists, but in other cases appeared not to influence attraction. Among the minor components identified in headspace extracts from males, 2,3-hexanedione and 2-hydroxyhexan-3-one appeared to be analytical artifacts or biosynthetic by-products, and were neither attractants nor synergists. The antagonistic effects of minor compounds produced by heterospecific males suggest that these compounds serve to maintain prezygotic reproductive isolation among some species that share pheromone components.

Associative learning is necessary for airborne pheromones to activate sexual arousal-linked brain areas of female rats

In rodents, urine-borne male pheromones include volatile organic compounds (VOCs) and major urinary proteins (MUPs). In mice, the attraction of females to male odor is reportedly acquired through associative learning with MUPs in some studies. Here, we found that VOC and MUP sex pheromones were differentiated in rats at around 8 weeks of age and that females separated from males at weaning showed no preference for male urine odor after sexual maturity. Olfactory preferences could be gained in females after repeated experience of VOC pheromones alone as well as male urine or a blend of synthetic VOC pheromones and recombinant MUPs. However, differences in acquired olfactory preferences for male urine were further revealed by neuro-immuno-histochemical studies. The blend exhibited neural activation in the main olfactory system (MOS), accessory system (AOS), and the ventromedial hypothalamus (VMH), indicating sexual arousal, whereas the VOC alone only caused neural activation of MOS. We suggest that olfactory preference is generated through repeated experience of either VOCs or a blend of VOCs and MUPs, but the neural activations related to sexual arousal have to be acquired through associative learning with MUPs in female rats. When adult female rats were separated from males before maturity, they lost their attraction to male urine odor. Female preference to volatiles in male urine could be gained by repeated experience of volatile and protein pheromones. Brain regions related to sexual arousal were activated by male urine in females with experience of VOCs together with MUPs but not in those experienced with VOCs alone. Associative learning between VOC and MUP pheromones is necessary for male urine odor-induced FOS responses in the key regions for sexual arousal/excitement in female rats.

Identification of Aggregation-Sex Pheromone Components for a "Living Fossil", the False Click Beetle, Palaeoxenus dohrni Horn (Coleoptera: Eucnemidae).

Insect pheromones have rarely been exploited in surveys or studies of rare and endangered species, despite their potential as effective and highly selective attractants for target species. Here, we report the identification, synthesis, and field bioassays of a male-produced aggregation-sex pheromone blend of a rare false click beetle species endemic to southern California, Dohrn's elegant eucnemid beetle, Palaeoxenus dohrni Horn (Coleoptera: Eucnemidae). This species is the only extant species in its genus and subfamily. Analyses of extracts of headspace volatiles collected from adult beetles revealed several male-specific compounds. Two of these compounds, identified as (E)-2-nonen-4-one and (R)-2-nonanol, elicited electroantennographic responses from antennae of beetles of both sexes. In field bioassays, a blend of the two compounds attracted both sexes, whereas the individual compounds were not attractive. The identification of an attractant pheromone should provide a useful tool for bioconservation and ecological studies of this iconic species.

Within-population variability in a moth sex pheromone blend, part 2: selection towards fixation

To understand how variation in sexual communication systems evolves, the genetic architecture underlying sexual signals and responses needs to be identified. Especially in animals where mating signals are important for mate recognition, and signals and responses are governed by independently assorting genes, it is difficult to envision how signals and preferences can (co)evolve. Moths are a prime example of such animals. In the noctuid moth Heliothis virescens, we found within-population variation in the female pheromone. In previous selection experiments followed by quantitative trait locus (QTL) analysis and expression analysis of candidate desaturase genes, we developed a model involving a trans-acting repressor of the delta-11-desaturase. In our current study with new selection lines, we fixed the most extreme phenotype and found a single underlying mutation: a premature stop codon in the first coding exon of delta-11-desaturase, which we could trace back to its origin in the laboratory. Interestingly, we found no pleiotropic effects of this knock-out mutation on the male physiological or behavioural response, or on growth or fertility. This finding is in contrast to Drosophila melanogaster, where a single desaturase gene affects both female pheromone production and male behavioural response, but similar to other Lepidoptera where these traits are under independent genetic control. To our knowledge, this is the first time that a single point mutation has been identified that underlies the phenotypic variation in the pheromone signal of a moth.

Tergal gland components of reproductively dominant honey bee workers have both primer and releaser effects on subordinate workers

The primer and releaser effects of dominant honey bee workers’ tergal gland pheromones are not known under queenless conditions. The Cape honey bee, Apis mellifera capensis, is the ideal model to investigate such question since workers normally reproductively dominate workers of all other subspecies. We determined the effects that short- and long-term exposure to pheromone blends from dominant A. m. capensis workers had on subordinate workers of A. m. scutellata. Three putative pheromonal blends, 1 (palmitic acid, oleic acid, n-heneicosene and n-tricosene), 2 (ethyl palmitate, ethyl oleate and ethyl stearate) and 3 (mixture of blends 1 + 2), were tested. All the three putative pheromonal blends elicited releaser effects in the form of retinue formation and primer effects by suppressing ovarian activation in workers. The resultant effects indicated that these pheromonal blends appear to play a role in establishing dominance among workers and hence regulating opportunities to reproduce.