Antennal Responses Research Articles

Attraction of Adults of Cyclocephala lunulata and Cyclocephala barrerai (Coleoptera: Scarabaeoidea: Melolonthidae) towards Bacteria Volatiles Isolated from Their Genital Chambers.

In the study of the chemical communication of adults of the Melolonthidae family, bacteria have been observed in the epithelium of the genital chamber; possibly, bacteria are involved in the production of sex attractants in their hosts. Therefore, it is important to identify the volatile organic compounds from bacteria (VOCsB) released by these microorganisms and study the biological activity stimulated by VOBCs in adults of Melolonthidae. In this study, bacteria were isolated from the genital chamber of Cyclocephala lunulata and Cyclocephala barrerai, from which VOCsB were extracted using static headspace solid-phase microextraction (SHS-SPME) and dynamic headspace Super Q solid-phase extraction (DHS-SPE) and analyzed using gas chromatography-mass spectrometry. The effect of VOCsB on the hosts and conspecifics was evaluated utilizing an olfactometer and electroantennography (EAG). Two species of Enterobacteria were isolated from the genital chamber of each female species, and VOCsB derived from sulfur-containing compounds, alcohols, esters, and fatty acids were identified. An attraction response was observed in olfactometry studies, and antennal responses to VOCsB were confirmed in EAG bioassays. With these results, new perspectives on the relationship between these beetles and their bacteria emerge, in addition to establishing a basis for management programs in the future.

Optimization and field demonstration of the Lygus pratensis (Hemiptera: Miridae) sex pheromone.

The plant bug Lygus pratensis Linnaeus is a widely distributed polyphagous herbivore that increasingly attains outbreak population levels on cotton in northwestern China. Although the sex pheromone of L. pratensis from the United Kingdom has been identified as hexyl butyrate, (E)-2-hexenyl butyrate and (E)-4-oxo-2-hexenal, at a ratio of 100:25:24, this volatile blend does not prove attractive to Chinese field populations. In this study, we identified and optimized the sex pheromone of L. pratensis strains from northwestern China. In coupled gas chromatography and electro-antennogram detection (GC-EAD) assays, three compounds within whole-body extracts of virgin L. pratensis females elicited antennal responses: hexyl butyrate, (E)-2-hexenyl butyrate and (E)-4-oxo-2-hexenal. In field trials, a 20:1:30 ratio blend was the most attractive to L. pratensis males. Traps baited with this synthetic pheromone blend present considerable advantages over traditional sweep-net sampling for L. pratensis population monitoring. It can readily be incorporated into monitoring schemes and integrated pest management packages.

Bumble Bees (Hymenoptera: Apidae) Respond to Moth (Lepidoptera: Noctuidae) Pheromone Components, Leading to Bee Bycatch in Monitoring Traps Targeting Moth Pests

Semiochemical-baited traps are commonly used to monitor moth pests and inform management decisions. Unfortunately, bee pollinators can be unintentionally captured, which reduces monitoring system efficiency and may negatively impact pollinator biodiversity and pollination services. We assessed the abundance and diversity of wild bees captured in semiochemical-baited traps designed to capture cutworm and armyworm (Lepidoptera: Noctuidae) pests in North America. Green Unitraps were baited with semiochemicals including: 1) species-specific noctuid pheromone lures; 2) food bait lures consisting of fermentation by-products; or 3) floral volatiles. Traps were positioned in canola (Brassica napus L.) and wheat (Triticum aestivum L.) fields in Alberta, Canada. We also explored the mechanisms of bee detection of moth pheromone components using electroantennogram (EAG) assays to assess the antennal response of two Bombus species. We found that more bumble bees (Hymenoptera: Apidae), and especially Bombus rufocinctus Cresson, were captured in traps baited with moth pheromone lures than in unbaited control traps. Fermentation by-product lures captured a similar low number of bees as unbaited traps, whereas floral volatile-based food bait lures captured more bees, comparable to capture in pheromone-baited traps. In general, more Bombus spp. were captured in traps positioned at canola vs. wheat fields, but the community composition was similar among crops. EAG assays indicate that sensory receptors on the antennae of B. rufocinctus Cresson and B. impatiens Cresson detect noctuid moth pheromones. Perception of chemical signals of a different insect order may be explained by structural similarities in pheromone components produced by both moths and bumble bees.

Electrophysiological Responses of the Beech Leaf-Mining Weevil, Orchestes fagi, to Seasonally-Variant Volatile Organic Compounds Emitted by American Beech, Fagus grandifolia.

The beech leaf-mining weevil, Orchestes fagi, is a common pest of European beech, Fagus sylvatica, and has recently become established in Nova Scotia, Canada where it similarly infests American beech, F. grandifolia. We collected volatile organic compounds (VOCs) emitted by F. grandifolia leaves at five developmental stages over one growing season and simultaneously analyzed them for volatile emissions and O. fagi antennal response using gas chromatography-electroantennographic detection (GC-EAD). Volatile profiles changed significantly throughout the growing season, shifting from primarily β-caryophyllene, methyl jasmonate, and simple monoterpene emissions to dominance of the bicyclic monoterpene sabinene during maturity. Two VOCs dominant during bud burst, (R)-(+)-limonene and geranyl-p-cymene, may be of biological relevance due to the highly specific oviposition period of O. fagi at this stage though antennal responses were inconclusive. Senescence showed a decrease in blend complexity with an increase in (Z)-3-hexenyl acetate and (Z)-3-hexen-1-ol as well as a resurgence of α-terpinene and geranyl-p-cymene. We present a novel electroantennal preparation for O. fagi. Antennae of both male and female O. fagi responded to the majority of detectable peaks for host volatiles presented via GC-EAD. Females displayed greater overall sensitivities and less specificity to host volatiles and it is hypothesized that this translates to more generalist olfaction than males. It is clear that olfactory cues are important physiologically though their implications on behaviour are still unknown. The results presented in this study provide a baseline and tools on which to connect the complex and highly time-specific phenology of both F. grandifolia and the destructive pest O. fagi through which olfactory-based lures can be investigated for monitoring systems.

Plant Volatiles Help Mediate Host Plant Selection and Attraction of the Spotted Lanternfly (Hemiptera: Fulgoridae): a Generalist With a Preferred Host.

Host plant volatiles play a key role in mediating plant-herbivore interactions. How an array of host plant volatiles guides host preference and attraction in the invasive polyphagous Lycorma delicatula (White), the spotted lanternfly (SLF), is largely unknown. A pernicious phloem feeder, SLF feeds on over 70 species of plants, some with high economic impact. To aid the development of detection and monitoring tools for SLF, we used a two-choice olfactometer to compare 14 host plant species for attraction, first to a blank control, and then to their preferred host Ailanthus altissima (Mill.) Swingle (Sapindales: Simaroubaceae), tree-of-heaven. SLF were significantly attracted to seven host plants compared to a blank control, but no host plant was more attractive than tree-of-heaven. We then used electroantennographic detection (EAD) to screen select host plants for EAD active compounds, hypothesizing that EAD-active plant volatiles act as kairomones and mediate SLF attraction to host plants. Out of 43 unique antennal responses, 18 compounds were identified and tested individually for attraction in a two-choice olfactometer against a blank control and then against methyl salicylate, the current best attractant. Eleven compounds were significantly attractive, and one, sulcatone, was more attractive than methyl salicylate. Blends of kairomones were then tested for attraction, revealing five blends that were significantly more attractive than methyl salicylate, and could be developed into lures for field testing. The presence of these kairomones in volatile profiles of 17 plant species is described. These findings support the hypothesis that the identified volatiles act as kairomones and function in attraction to host plants.

Antennal sensitivity to female sex pheromone compounds of Spodoptera frugiperda males (Lepidoptera: Noctuidae) and associated field behaviour

AbstractThe fall armyworm (FAW), Spodoptera frugiperda (J. E. Smith) (Lepidoptera: Noctuidae), is one of the most important insect pests of corn, sorghum, rice, and grasses. The sex pheromone produced by S. frugiperda is composed of a mixture of esters. In this study, I determined the antennal responses of FAW males from 22 populations in Mexico to the components of the sex pheromone of this species: (Z)‐7‐dodecenyl acetate (Z7‐12:OAc), (Z)‐9‐tetradecenyl acetate (Z9‐14:OAc), and (Z)‐11‐hexadecenyl acetate (Z11‐16:OAc) at four doses (0.01, 0.1, 1, and 10 μg). In addition, I evaluated the behavioural activity of single compounds in the field. The largest antennal responses of FAW males from all the sampled regions were elicited by Z9‐14:OAc (all doses evaluated) and Z7‐12:OAc (0.01, 0.1, and 1 μg). The male antennal responses evoked by Z11‐16:OAc were smaller but similar to responses to Z7‐12:OAc at lower doses (0.01 and 0.1 μg). In the field test, Z9‐14:OAc produced significantly higher captures of S. frugiperda males compared to Z7‐12:AOc and Z11‐16:OAc. Antennal responses were related to captures obtained in the field, supported by the positive correlation of these variables [electroantennography (EAG) response and behaviour], with the exception of Z7‐12:OAc, which elicited relatively large EAG responses but did not produce high captures of S. frugiperda. These results are of importance to agriculture, enabling the implementation of better methods of monitoring and controlling this pest, and support the suggestion that a mixture of Z9‐14:OAc and Z7‐12:OAc could represent an effective attractant for all evaluated populations of S. frugiperda in Mexico.

Dung mimicry: the function of volatile emissions and corolla patterning in fly-pollinated Wurmbea flowers.

It has been suggested that flowers of some angiosperms mimic vertebrate faeces (dung) in order to exploit insect pollinators that utilize faeces as a source of food and/or oviposition sites. We investigated a potential case of mimicry in Wurmbea elatior (Colchicaceae), a lily that exhibits a faecal odour and pattern of dark spots on the corolla. We found that W.elatior is pollinated by a broad assemblage of coprophagous flies and is dependent on pollinator visits for seed production. The flowers emit volatiles that are characteristic of vertebrate faeces, and three of these compounds - skatole, indole, and an unidentified compound - elicited electrophysiological antennal responses from flies. Artificial flowers laced with indole and skatole or skatole alone attracted the same assemblage of flies as was recorded on flowers of W.elatior. Spotted artificial flowers attracted twice as many flies as did those lacking spots. Experimental addition of indole and skatole to flowers of Wurmbea kraussii, a congener with unscented flowers pollinated by hoverflies, induced a shift to an insect visitor assemblage dominated by coprophagous flies. This study clarifies the roles of volatile emissions (particularly skatole) and visual signals in floral dung mimicry.

Pheromone Chemistry of the Citrus Borer, Diploschema rotundicolle (Coleoptera: Cerambycidae).

The citrus borer, Diploschema rotundicolle, is a Neotropical longhorn beetle that has become a serious citrus pest in southern South America. Management strategies for this insect rely on trimming off damaged shoots, which is expensive and inefficient. We studied the chemical communication system in D. rotundicolle in search of attractants for monitoring or control. GC-MS and enantioselective GC analyses of volatile extracts from field-collected adults showed that males produce (R)-3-hydroxy-2-hexanone, irregularly accompanied by minor amounts of 2,3-hexanediol (all four stereoisomers) and 2,3-hexanedione. Males emit the compounds only at night, when the adults are active. GC-EAD analyses of natural and synthetic compounds showed that both male and female antennae respond to the natural enantiomer (R)-3-hydroxy-2-hexanone, suggesting that it may function as an aggregation-sex pheromone as seen in many cerambycines. The non-natural (S) enantiomer as well as the minor component 2,3-hexanediol did not trigger antennal responses. Field tests with the racemic 3-hydroxy-2-hexanone, enantiomerically pure (R)-3-hydroxy-2-hexanone, as well as a mixture of racemic 3-hydroxy-2-hexanone and 2,3-hexanediol, showed in all cases low capture levels of D. rotundicolle. However, increasing the elevation of the trap and the emission rate of dispensers enhanced field captures in traps baited with racemic hydroxyketone. Incidental catches of another native cerambycine, Retrachydes thoracicus, in traps baited with 3-hydroxy-2-hexanone are also reported. This is the first report of pheromone chemistry in the genus Diploschema and in the tribe Torneutini, reaffirming the pheromone parsimony well established for the Cerambycinae. Potential factors explaining the weak attraction of D. rotundicolle in the field are discussed.

(7Z)-Tricosene Improves Pheromone Trap Catch of Raspberry Bud Moth, Heterocrossa rubophaga.

Heterocrossa rubophaga, the raspberry bud moth, is a pest of commercial Rubus berry crops and wild Rubus species. Its pheromone was initially identified as a single component, (7Z)-nonadecen-11-one. Here we report further investigation of this carposinid pheromone including volatile collection, gland extraction, mass spectrometry, microchemical analysis, electrophysiology and field testing. The alkene (7Z)-tricosene was identified from female gland extracts and the synthetic compound gave antennal responses from the male moth. Field testing of (7Z)-tricosene showed that it was unattractive alone but in combination with (7Z)-nonadecen-11-one it more than doubled male moth trap catch for all doses tested compared to that of (7Z)-nonadecen-11-one alone. We recommend a blend of 300µg of (7Z)-nonadecen-11-one and 300µg of (7Z)-tricosene as an improved monitoring tool for raspberry bud moth for use by berry growers. This is the second report of the Z-alkene as a pheromone component in the Carposinidae family among the three carposisnid pheromones identified to date.

Identification of a hyperactive pheromone analog in field tests of pheromone mimics for two click beetle species in the genus Cardiophorus (Coleoptera: Elateridae)

Females of two click beetle species, Cardiophorus tenebrosus and C. edwardsi (Coleoptera: Elateridae), produce methyl (3R,6E)-2,3-dihydrofarnesoate as their sex pheromone. We had serendipitously discovered that males of both species were also strongly attracted to (R)-fuscumol acetate ((E)-6,10-dimethylundeca-5,9-dien-2-yl acetate), a known longhorned beetle (Coleoptera: Cerambycidae) pheromone, due to its structural similarities to the click beetle pheromone. To further investigate the specificity of the responses of Cardiophorus males, additional analogs with different chain lengths and structural relationships compared to the natural pheromone were synthesized and tested. In field and electroantennogram bioassays, only fuscumol propionate ((E)-6,10-dimethylundeca-5,9-dien-2-yl propionate) elicited strong responses from Cardiophorus males, indicating that they were able to distinguish chain length and spatial relationships between the structural elements. In field trials, C. tenebrosus males were attracted equally to the analog and their natural pheromone, but the pheromone elicited stronger antennal responses from males. In contrast, traps baited with fuscumol propionate caught approximately 26 times as many C. edwardsi males compared to traps baited with the natural pheromone, although the analog elicited significantly smaller antennal responses from C. edwardsi males. Thus, in terms of behavioral responses, fuscumol propionate appears to be acting as a hyperactive pheromone mimic, a phenomenon which has rarely been observed in insect semiochemistry.

Floral Odors Can Interfere With the Foraging Behavior of Parasitoids Searching for Hosts

Plants produce distinct blends of volatile compounds that attract pollinators (floral odors) or natural enemies of insect herbivores (herbivore-induced plant volatiles). The admixture of these blends in the atmosphere may alter the attraction of insect mutualists and ultimately affect plant fitness. Here, using synthetic blends of Brassica rapa floral volatiles and real B. rapa flowers, we investigated how floral odors impact the foraging behavior of parasitoids. In an olfactometer setting, floral odors reduced the attractiveness of plants infested by herbivores to parasitoids by 43.5% and affected four out of five parasitoid species tested. Additionally, experiments with the parasitoid Cotesia glomerata revealed that the effects of floral odors are dose-dependent and that floral odors were less disruptive under wind tunnel conditions than under olfactometer conditions. Electroantennogram recordings showed that C. glomerata antennae do respond to floral compounds, but that floral compounds do not inhibit antennal responses to herbivore-induced leaf volatiles. In conclusion, floral odors can act as background pollutants decreasing the attractiveness of chemical blends used by natural enemies to locate their hosts. Under natural conditions, such interferences could affect the outcome of tritrophic interactions and may play an important role in the evolution of plant volatile signaling.

Identification of a female-produced pheromone in a destructive invasive species: Asian longhorn beetle, Anoplophora glabripennis

Male-produced pheromone components have been reported in the Asian longhorn beetle, Anoplophora glabripennis (Motschulsky) (Coleoptera: Cerambycidae), but field attraction to these components has been less than overwhelming. Female ALBs were observed rhythmically extending the genitalia in a manner reminiscent of female calling behaviors in other cerambycid species. We thus hypothesized that female ALBs release volatile pheromone while performing this sex-specific behavior. A group of sesquiterpenes, including a major compound α-longipinene and several minor ones α-cubebene, α-ylangene, (−)-α-copaene, α-bergamotene, β-caryophyllene, and α-farnesene, found in genitalia extracts from virgin females elicited male antennal responses. Y-tube olfactometer assays indicated significant attraction of α-longipinene to both sexes in either the presence or absence of host volatiles. This compound was also detected in genitalia extracts from virgin males, though in much lower quantities than in females. Dose–response experiments conducted in the y-tube olfactometer and field both revealed that α-longipinene was attractive at the higher doses, but not at the lower ones. In the field, traps baited with a blend containing α-longipinene, α-cubebene, and β-caryophyllene captured significantly more ALB than solvent controls. The trap catches of α-longipinene combined with either the minor components or host compounds were both greater than those of α-longipinene alone, but the difference was not significant. These results indicate that α-longipinene is a new type of female-produced volatile pheromone in ALB, and the attraction may be synergistically enhanced by several minor components. Sesquiterpenes may play an important role in intraspecies chemical communication of this insect.

Cuticular hydrocarbons C14-C36 are potential contact pheromonal elements modulating some behaviors in Zygogramma bicolorata (Coleoptera: Chrysomelidae)

Chrysomelid beetle, Zygogramma bicolorata (Pallister, 1953) (Coleoptera: Chrysomelidae), is an important biocontrol agent for the weed Parthenium hysterophorus. The insect spends its whole life on the same plant, which acts as an essential site for feeding, mating and oviposition. These insects were studied for repeated mating, either to same or different mates, and the results indicated both polyandrous and polygamous mating with same-pair mating preferences. Apart from this, a preliminary bioassay was performed individually for both the sexes to detect the presence of contact pheromones. These chemicals, ranging from C14 to C36 and often known as cuticular hydrocarbons (straight and branched), were further identified by reading their mass spectra. Although the hydrocarbon profiles of males and females resembled each other qualitatively, the compounds showed a significant difference with respect to their relative proportions. The antennal response to some of the corresponding synthetic straight chain alkanes (Pentacosane, Hexatriacontane, Docosane, Tetracosane, Heneicosane, Hexacosane, Octadecane, Eicosane and Tetratriacontane) were also tested using electroantennography (EAG) at four different concentrations (0.1%, 0.01%, 0.001% and 0.0001%). The mean EAG response obtained was observed to be sex dependent for all compounds tested. The antennae of female responded strongly to these compounds with Tetratriacontane eliciting the highest response of – 0.684 mV at the concentration 0.01%. The difference in the responses may be attributed to the differences in the release rates of these compounds and the sensitivity of antennal responses between the sexes.

Olfactory co-receptor is involved in host recognition and oviposition in Ophraella communa (Coleoptera: Chrysomelidae).

Common ragweed (Ambrosia artemisiifolia) is a notorious invasive weed that has spread across most temperate regions of the world. The beetle (Ophraella communa) is considered to be an effective control agent against A. artemisiifolia. As an oligophagous insect, its olfactory system is extremely important for host seeking in the wild. To the best of our knowledge, there is no report on the molecular mechanisms underlying olfaction recognition in this beetle. Hence, in this study, we characterized the odorant receptor co-receptor of O. communa and named it as 'OcomORco'. Real-time quantitative PCR (qRT-PCR) showed that, compared to the control treatment, RNA interference (RNAi) strongly reduced the expression of OcomORco by 89% in male and 90% in female beetles. Electroantennogram assay showed that the antennal response of both male and female beetles to four volatiles of A. artemisiifolia was significantly reduced. The injected male or female beetles lost their preference for plant leaves as observed in the behavioural tests. In addition, disruption of the expression of OcomORco resulted in a reduction of oviposition, while there was no difference in larval hatching rate between control and knockdown females. We demonstrated that OcomORco plays a vital role in olfactory perception and host search in O. communa, and it is involved in oviposition in an indirect way.

Copitarsia decolora Guen\xe9e (Lepidoptera: Noctuidae) females avoid larvae competition by detecting larvae damaged plants

Herbivory insects can discriminate the quality of a host plant for food or oviposition, by detecting the volatile organic compounds (VOC’s) released by the plant, however, damaged plants may release a different VOC’s profile modifying the insects’ response. We tested if the VOC’s profile from damaged plants affected the response of Copitarsia decolora as these moths oviposit preferably around undamaged host plants. We assessed the response in wind tunnel conditions of C.decolora mated females to volatiles collected by dynamic headspace from 30–40 d old cabbage undamaged plants and mechanical and larval damaged plants. Headspace volatile compounds from undamaged cabbage plants were more attractive to mated females than those from larval and mechanical damaged cabbage plants. Moths stimulated with headspace volatiles from undamaged plants performed more complete flight and ovipositor displays than those moths stimulated with headspace volatiles from damaged cabbage plants. A mixture of synthetic compounds identified from undamaged cabbages elicited similar antennal and wind tunnel responses in mated females as headspace volatiles from undamaged cabbage plants. C. decolora females may discriminate between damaged and undamaged host plants by detecting their VOC’s profiles as a strategy to avoid unsuitable plants for their offspring increasing their fitness.

Heterogeneous expression of the ammonium transporter AgAmt in chemosensory appendages of the malaria vector, Anopheles gambiae

Ammonia is one of the principal kairomones originating from human and other animal emanations and in that context, plays an essential role in the host-seeking behaviors of the malaria vector mosquito Anopheles gambiae. Nevertheless, despite its importance in directing host-seeking, the mechanisms underlying ammonia detection in the mosquito olfactory system remains largely unknown. In addition to ongoing efforts to identify and characterize the molecular receptors that underlie ammonia sensitivity, previous studies have revealed a prominent role for ammonium transporters (Amt) in modulating antennal and behavioral responses in Drosophila melanogaster and An. gambiae. In the former, localization of DmAmt in antennal sensilla to auxiliary cells surrounding the ammonia sensory neurons led to the hypothesis that its role was to clear excess ammonium ions in the sensillar lymph. In the latter, RT-PCR and heterologous expression have been used to examine the expression and functional characteristics of the An. gambiae ammonium transporter, AgAmt. We now employ advanced transgenic tools to comprehensively examine AgAmt spatial localization across the peripheral chemosensory appendages in larvae and adult female An. gambiae. In the larval antennae, AgAmt appears localized in both neuronal and auxiliary cells. In contrast to D. melanogaster, in the adult antennae, AgAmt-derived signals are observed in both non-neuronal auxiliary cells and in sensory neurons in ammonia-responsive basiconic and coeloconic sensilla. In the maxillary palps, labella, and tarsi, AgAmt appears restricted to sensory neurons. We have also characterized the responses to ammonia of adult antennal coeloconic sensilla and maxillary palp capitate pegs revealing a correlation between sensillar AgAmt expression and ammonia sensitivity. Taken together, these data suggest that AgAmt may play heterogeneous roles in the adult and larval chemosensory apparatus and potentially broad utility as a supra-receptor target in mosquito control.

The Role of (E)-2-octenyl Acetate as a Pheromone of Bagrada hilaris (Burmeister): Laboratory and Field Evaluation.

The pentatomid bug Bagrada hilaris is a key pest of brassicaceous crops in several areas of the world. Previous studies suggest that mate location of this species is mediated by volatile chemicals produced by males, among which the main compound is (E)-2-octenyl acetate. However, the possible attraction of males, females, and nymphs to this compound has not yet been specifically tested. In this study, we tested the response of B. hilaris females, males, and nymphs to (E)-2-octenyl acetate using an electroantennogram (EAG) and olfactometer in the presence or absence of a host plant. Moreover, (E)-2-octenyl acetate as an attractant lure in field trap bioassays was evaluated. EAG recordings showed that this compound evokes antennal responses in B. hilaris females. Olfactometer behavioral responses showed that females and nymphs were attracted to (E)-2-octenyl acetate, while males showed no attraction. In the field trap bioassays, captures were obtained in traps baited with 5 and 10 mg of (E)-2-octenyl acetate, while in traps loaded with 2 mg and control traps, there were no recorded catches. These results suggest the involvement of (E)-2-octenyl acetate in intraspecific interactions of this species.

Effect of (E4, Z6)-4,6-Hexadecadienal in attraction of Stathmopoda masinissa with its pheromone components of Korean population

Abstract Timely insecticidal application for Stathmopoda masinissa Meyrick (Lepidoptera: Stathmopodidae), is important, for reducing damage to persimmon (Diospyros kaki Thunb.), an important tree fruit cultivated in Korea. In this regard, the early and precise detection of adult S. masinissa is desirable. In this study, we report the effect of (E4,Z6)-4,6-hexadecadienal (E4,Z6-16Ald) with sex pheromone components in attracting S. masinissa males. The sex pheromone of S. masinissa in the Korean population comprised two components, (E4,Z6)-4,6-hexadecadienyl acetate (E4,Z6-16Ac) and (E4,Z6)-4,6-hexadecadienol (E4,Z6-16OH). It was shown that the E4,Z6-16Ald acts as a synergist of E4,Z6-16Ac for attracting S. masinissa in the Japanese population. To test whether E4,Z6-16Ald could be used as an attractant in the Korean population, the E4,Z6-16Ald with the two pheromone components was evaluated in attracting S. masinissa males. Electroantennography (EAG) assays were performed to determine the antennal responses of S. masinissa males to the two pheromone components and E4,Z6-16Ald tested. A field attraction test with a combination of pheromones and E4,Z6-16Ald was carried out for 3 years in three different regions in Korea. E4,Z6-16Ald elicited as high a response as the two pheromone components. A mixture of the two pheromone components and E4,Z6-16Ald and a mixture of E4,Z6-16Ac and E4,Z6-16Ald attracted more S. masinissa males than a mixture of E4,Z6-16Ac and E4,Z6-16OH, the pheromone of Korean population. This new pheromone lure formulation with E4,Z6-16Ald is expected to contribute to the precise detection of S. masinissa by luring males to pheromone-baited traps.

Pheromonal activities of the bombykol isomer, (10E,12E)-10,12-hexadecadien-1-ol, in the pheromone gland of the silkmoth Bombyx mori

Bombykol (EZ) is the single component of the female sex pheromone in the silkmoth Bombyx mori. EZ alone evokes full courtship behaviors from conspecific males; however, its geometric isomer (EE) was consistently detected in the pheromone glands (PG) of 16 B. mori strains and a field population of the wild silkmoth Bombyx mandarina, which also uses EZ as the single pheromone component. We investigated the pheromonal activities of EE using a commercial hybrid strain of B. mori, Kinshu × Showa. The behavioral assay demonstrated that a 104–105-fold higher dose of EE than EZ was able to elicit behavioral responses from males. To elucidate whether the trace contaminant of EZ in the EE standard is responsible for these responses, we examined the responses of male antennae to EE using a gas chromatograph-electroantennographic detector system (GC-EAD). The EE, at high doses elicited marginal responses from the male antennae. We next examined antennal and behavioral responses of B. mori whose BmOR1 gene, which is responsible for the reception of bombykol, was knocked out. The knockout of BmOR1 resulted in the complete loss of antennal and behavioral responses to EE and EZ, demonstrating that if EE itself is active, it induces these responses via the incidental stimulation of BmOR1, not via the stimulation of EE-specific receptors. The existence of EE in the PG of B. mori and B. mandarina is discussed from the viewpoints of pheromone biosynthesis and the evolution of pheromone communication systems.

Terpenoid-Induced Feeding Deterrence and Antennal Response of Honey Bees.

Multiple interacting stressors negatively affect the survival and productivity of managed honey bee colonies. Pesticides remain a primary concern for beekeepers, as even sublethal exposures can reduce bee immunocompetence, impair navigation, and reduce social communication. Pollinator protection focuses on pesticide application guidelines; however, a more active protection strategy is needed. One possible approach is the use of feeding deterrents that can be delivered as an additive during pesticide application. The goal of this study was to validate a laboratory assay designed to rapidly screen compounds for behavioral changes related to feeding or feeding deterrence. The results of this investigation demonstrated that the synthetic Nasonov pheromone and its terpenoid constituents citral, nerol, and geraniol could alter feeding behavior in a laboratory assay. Additionally, electroantennogram assays revealed that these terpenoids elicited some response in the antennae; however, only a synthetic Nasonov pheromone, citral, and geraniol elicited responses that differed significantly from control and vehicle detections.