Carbon Dioxide, Methane, and Synthetic Cattle Breath Volatiles Attract Host-Seeking Stable Flies, Stomoxys calcitrans.

Stable flies, Stomoxys calcitrans (L.), are blood-feeding ectoparasites of cattle. Host-seeking stable flies respond to various cattle host cues, but a potential role of cattle breath gases [carbon dioxide (CO2), methane (CH4)] and cattle breath volatiles (acetone, isoprene, 2-butanone, 2-propanol, propionic acid, 3-methyl butyric acid, phenol), alone or in combination, on host-seeking behavior of stable flies has not yet been comprehensively investigated. In laboratory and greenhouse experiments, we tested the hypotheses that (1) CO2 and CH4 interactively attract stable flies, (2) CO2 'gates' attraction of stable flies to CH4, and (3) breath volatiles on their own, or in combination with both CO2 and CH4, attract stable flies. In Y-tube olfactometer experiments, the blend of CH4 (0.5%) and CO2 (1%) in breathing air ('b-air') attracted significantly more female flies than CH4, or CO2, in b-air. The flies' responses to CH4 were contingent upon their prior or concurrent exposure to CO2. In two-choice experiments in a large greenhouse compartment, significantly more flies landed on the host-look-alike barrel that disseminated a blend of CO2 and CH4 in b-air (CO2/CH4/b-air) than on the barrel disseminating either b-air or CO2. Moreover, significantly more flies landed on the barrel that disseminated synthetic breath volatiles (SBVs) than on the barrel disseminating b-air. The blend of CO2/CH4/b-air and SBVs elicited more fly landings on barrels than CO2/CH4/b-air but not than SBVs. SBVs, possibly combined with both CH4 and CO2, could be developed as a lure to enhance trap captures of stable flies in livestock production facilities.

Blacklegged ticks, Ixodes scapularis, reduce predation risk by eavesdropping on communication signals of Formica oreas thatching ants.

Ticks spend most of their life inhabiting leaf litter and detritus where they are protected from sun but preyed upon by ants. Ants secrete chemical communication signals to coordinate group tasks such as nest defence. Ticks that avoid ant semiochemicals-as indicators of ant presence-would reduce predation risk by ants. We tested the hypotheses that: (i) chemical deposits from the thatching ant Formica oreas deter blacklegged ticks, Ixodes scapularis, (ii) deterrent semiochemicals originate from the ants' poison and/or Dufour's gland(s), and (iii) tick-deterrent semiochemicals serve as alarm-recruitment pheromone components in F. oreas. In two-choice olfactometer bioassays, filter paper soiled with ant chemical deposits significantly deterred female and male ticks. Poison and Dufour's gland extracts deterred ticks in combination but not alone. Gas chromatographic-mass spectrometric analyses of gland extracts revealed formic acid as the major constituent in the poison gland and eight hydrocarbons as constituents in the Dufour's gland. Synthetic formic acid and hydrocarbons deterred ticks only when combined. F. oreas workers sprayed both formic acid and hydrocarbons when distressed. A synthetic blend of these compounds elicited alarm-recruitment responses by F. oreas in behavioural bioassays. All results combined indicate that ticks eavesdrop on the ants' communication system.

Non-targeted metabolomics aids in sex pheromone identification: a proof-of-concept study with the triangulate cobweb spider, Steatoda triangulosa.

Targeted metabolomics has been widely used in pheromone research but may miss pheromone components in study organisms that produce pheromones in trace amount and/or lack bio-detectors (e.g., antennae) to readily locate them in complex samples. Here, we used non-targeted metabolomics-together with high-performance liquid chromatography-mass spectrometry (HPLC-MS), gas chromatography-MS, and behavioral bioassays-to unravel the sex pheromone of the triangulate cobweb spider, Steatoda triangulosa. A ternary blend of three contact pheromone components [N-4-methylvaleroyl-O-isobutyroyl-L-serine (5), N-3-methylbutyryl-O-isobutyroyl-L-serine (11), and N-3-methylbutyryl-O-butyroyl-L-serine (12)] elicited courtship by S. triangulosa males as effectively as female web extract. Hydrolysis of 5, 11 and 12 at the ester bond gave rise to two mate-attractant pheromone components [butyric acid (7) and isobutyric acid (8)] which attracted S. triangulosa males as effectively as female webs. Pheromone components 11 and 12 are reported in spiders for the first time, and were discovered only through the use of non-targeted metabolomics and GC-MS. All compounds resemble pheromone components previously identified in widow spiders. Our study provides impetus to apply non-targeted metabolomics for pheromone research in a wide range of animal taxa.

Synergistic attraction of Western black-legged ticks, Ixodes pacificus, to CO2 and odorant emissions from deer-associated microbes.

Foraging ticks reportedly exploit diverse cues to locate their hosts. Here, we tested the hypothesis that host-seeking Western black-legged ticks, Ixodes pacificus, and black-legged ticks, I. scapularis, respond to microbes dwelling in sebaceous gland secretions of white-tailed deer, Odocoileus virginianus, the ticks' preferred host. Using sterile wet cotton swabs, microbes were collected from the pelage of a sedated deer near forehead, preorbital, tarsal, metatarsal and interdigital glands. Swabs were plated on agar, and isolated microbes were identified by 16S rRNA amplicon sequencing. Of 31 microbial isolates tested in still-air olfactometers, 10 microbes induced positive arrestment responses by ticks, whereas 10 others were deterrent. Of the 10 microbes prompting arrestment by ticks, four microbes-including Bacillus aryabhattai (isolates A4)-also attracted ticks in moving-air Y-tube olfactometers. All four of these microbes emitted carbon dioxide and ammonia as well as volatile blends with overlapping blend constituents. The headspace volatile extract (HVE) of B. aryabhattai (HVE-A4) synergistically enhanced the attraction of I. pacificus to CO2. A synthetic blend of HVE-A4 headspace volatiles in combination with CO2 synergistically attracted more ticks than CO2 alone. Future research should aim to develop a least complex host volatile blend that is attractive to diverse tick taxa.

Origin, structure and functional transition of sex pheromone components in a false widow spider.

Female web-building spiders disseminate pheromone from their webs that attracts mate-seeking males and deposit contact pheromone on their webs that induces courtship by males upon arrival. The source of contact and mate attractant pheromone components, and the potential ability of females to adjust their web's attractiveness, have remained elusive. Here, we report three new contact pheromone components produced by female false black widow spiders, Steatoda grossa: N-4-methylvaleroyl-O-butyroyl-L-serine, N-4-methylvaleroyl-O-isobutyroyl-L-serine and N-4-methylvaleroyl-O-hexanoyl-L-serine. The compounds originate from the posterior aggregate silk gland, induce courtship by males, and web pH-dependently hydrolyse at the carboxylic-ester bond, giving rise to three corresponding carboxylic acids that attract males. A carboxyl ester hydrolase (CEH) is present on webs and likely mediates the functional transition of contact sex pheromone components to the carboxylic acid mate attractant pheromone components. As CEH activity is pH-dependent, and female spiders can manipulate their silk's pH, they might also actively adjust their webs' attractiveness.

Identification of the Major Sex Pheromone Component of the Click Beetle Agriotes ferrugineipennis.

Synthetic sex pheromone lures are useful tools to monitor and control populations of adult click beetles (Coleoptera: Elateridae). However, sex pheromones for Agriotes click beetle species native to North America have yet to be identified. Here we report the identification and field testing of the sex pheromone of Agriotes ferrugineipennis. Headspace volatiles from female beetles were collected on Porapak Q, and aliquots of Porapak extract were analyzed by gas chromatographic-electroantennographic detection (GC-EAD) and GC-mass spectrometry. 7-Methyloctyl 7-methyloctanoate (7Me7Me) emitted by females was more abundant and elicited much stronger responses from male antennae than the aldehydes octanal and nonanal and the ketone 6,10,14-trimethyl-2-pentadecanone. In a field experiment, captures of A. ferrugineipennis males in traps baited with candidate pheromone components exceeded those of unbaited control traps, on average by nearly 1,200 times. Neither the ketone nor the aldehydes as lure constituents appeared to alter captures of males in 7Me7Me-baited traps. We conclude that 7Me7Me is the major, and possibly the only, sex attractant pheromone component of female A. ferrugineipennis.

Identification of the Trail Pheromone of the Pavement Ant Tetramorium immigrans (Hymenoptera: Formicidae).

Four species of Tetramorium pavement ants are known to guide foraging activities of nestmates via trail pheromones secreted from the poison gland of worker ants, but the trail pheromone of T. immigrans is unknown. Our objectives were to (1) determine whether poison gland extract of T. immigrans workers induces trail-following behavior of nestmates, (2) identify the trail pheromone, and (3) test whether synthetic trail pheromone induces trail-following behavior of workers. In laboratory no-choice bioassays, ants followed poison-gland-extract trails farther than they followed whole-body-extract trails or solvent-control trails. Gas chromatographic-electroantennographic detection (GC-EAD) analyses of poison gland extract revealed a single candidate pheromone component (CPC) that elicited responses from worker ant antennae. The CPC mass spectrum indicated, and an authentic standard confirmed, that the CPC was methyl 2-methoxy-6-methylbenzoate (MMMB). In further laboratory no-choice bioassays, ants followed poison-gland-extract trails (tested at 1 ant equivalent) and synthetic MMMB trails (tested at 0.35 ant equivalents) equally far, indicating that MMMB is the single-component trail pheromone of T. immigrans. Moreover, in laboratory two-choice bioassays, ants followed MMMB trails ~ 21-times farther than solvent-control trails. In field settings, when T. immigrans colonies were offered a choice between two paper strips treated with a synthetic MMMB trail or a solvent-control trail, each leading to an apple bait, the MMMB trails efficiently recruited nestmates to baits.

All sugars ain't sweet: selection of particular mono-, di- and trisaccharides by western carpenter ants and European fire ants.

Ants select sustained carbohydrate resources, such as aphid honeydew, based on many factors including sugar type, volume and concentration. We tested the hypotheses (H1-H3) that western carpenter ants, Camponotus modoc, seek honeydew excretions from Cinara splendens aphids based solely on the presence of sugar constituents (H1), prefer sugar solutions containing aphid-specific sugars (H2) and preferentially seek sugar solutions with higher sugar content (H3). We further tested the hypothesis (H4) that workers of both Ca. modoc and European fire ants, Myrmica rubra, selectively consume particular mono-, di- and trisaccharides. In choice bioassays with entire ant colonies, sugar constituents in honeydew (but not aphid-specific sugar) as well as sugar concentration affected foraging decisions by Ca. modoc. Both Ca. modoc and M. rubra foragers preferred fructose to other monosaccharides (xylose, glucose) and sucrose to other disaccharides (maltose, melibiose, trehalose). Conversely, when offered a choice between the aphid-specific trisaccharides raffinose and melezitose, Ca. modoc and M. rubra favoured raffinose and melezitose, respectively. Testing the favourite mono-, di- and trisaccharide head-to-head, both ant species favoured sucrose. While both sugar type and sugar concentration are the ultimate cause for consumption by foraging ants, strong recruitment of nest-mates to superior sources is probably the major proximate cause.

Limoniic Acid and Its Analog as Trap Lures for Pest Limonius Species (Coleoptera: Elateridae) in North America.

Four species of Limonius wireworms (Coleoptera: Elateridae), L. californicus, L. canus, L. infuscatus and L. agonus, are serious crop pests in North America. Limoniic acid, (E)-4-ethyloct-4-enoic acid, has been reported as a sex pheromone component of female L. californicus and L. canus, and a sex attractant for male L. infuscatus. In the same study, both limoniic acid and the analog (E)-5-ethyloct-4-enoic acid were highly attractive in field experiments. Moreover, six carboxylic acids in headspace volatiles of Limonius females elicited responses from male antennae but were not tested for behavioral activity. Here, we report trap catch data of Limonius spp. obtained in field experiments at 27 sites across North America. All four Limonius species were attracted to limoniic acid and to the analog but not to the carboxylic acids. Adding these carboxylic acids to limoniic acid, or to the analog, reduced its attractiveness. In dose-response studies, trap lures containing 0.4 mg or 4 mg of limoniic acid afforded large captures of L. californicus and L. infuscatus. Neither limoniic acid nor the analog were deterrent to other elaterid pest species. The broad attractiveness of limoniic acid to Limonius spp., and its non-deterrent effect on heterogeners, may facilitate the development of generic pheromone-based monitoring and management tools for multiple click beetle species.

Cheese and cheese infusions: ecological traps for mosquitoes and spotted wing Drosophila.

BACKGROUND: Harnessing insect ecology for insect control is an innovative concept that seeks to exploit, among others, insect-microbe ecological interactions for improved control of pest insects. Microbe-produced cheese odour attracts several dipterans, including host-seeking mosquitoes, but this phenomenon has not been thoroughly explored for mosquito control. Here we tested the hypothesis that attraction of mosquitoes to cheese odour can be exploited as an ecological trap for mosquito control. RESULTS: In laboratory and/or field experiments, we show that (i) each of five cheese varieties tested (Raclette, Pecorino, Brie, Gruyere, Limburger) strongly attracts female Aedes aegypti and Culex pipiens; (ii) cheese infusions, or headspace odourant extracts (HOEs) of cheese infusions, significantly affect oviposition choices by mosquitoes, (iii) HOEs contain at least 13 odourants; (iv) in field settings, cheese infusions more effectively stimulate mosquito oviposition than positive bluegrass infusion controls, and also capture (by drowning) the spotted wing Drosophila, Drosophila suzukii; and (v) home-made cheese infusions modulate oviposition choices by mosquito females and affect the survivorship of their offspring larvae. CONCLUSION: Our data show that microbial metabolites associated with cheese are attractive to mosquito females seeking hosts and oviposition sites and are likely toxic to mosquito larvae. These microbes and their metabolites could thus be co-opted for both the attract, and the kill, function of 'attract & kill' mosquito control tactics. Implementation of customizable and non-conventional nutritional media as microbe-based ecological traps presents a promising concept which exploits insect ecology for insect control. © 2021 Society of Chemical Industry.

Attraction of Brown Marmorated Stink Bugs, Halyomorpha halys, to Blooming Sunflower Semiochemicals.

The polyphagous invasive brown marmorated stink bug, Halyomorpha halys, reportedly discriminates among phenological stages of host plants. To determine whether olfaction is involved in host plant stage discrimination, we selected (dwarf) sunflower, Helianthus annuus, as a model host plant species. When adult females of a still-air laboratory experiment were offered a choice of four potted sunflowers at distinct phenological stages (vegetative, pre-bloom, bloom, seeding), most females settled onto blooming plants but oviposited evenly on plants of all four stages. In moving-air two-choice olfactometer experiments, we then tested each plant stage versus filtered air and versus one another, for attraction of H. halys females. Blooming sunflowers performed best overall, but no one plant stage was most attractive in all experiments. Capturing and analyzing (by GC-MS) the headspace odorants of each plant stage revealed a marked increase of odorant abundance (e.g., monoterpenes) as plants transitioned from pre-bloom to bloom. Analyzing the headspace odorant blend of blooming sunflower by gas chromatographic-electroantennographic detection (GC-EAD) revealed 13 odorants that consistently elicited responses from female H. halys antennae. An 11-component synthetic blend of these odorants attracted H. halys females in laboratory olfactometer experiments. Furthermore, in field settings, the synthetic blend enhanced the attractiveness of synthetic H. halys pheromone as a trap lure, particularly in spring (April to mid-June). A simpler yet fully effective sunflower semiochemical blend could be developed and coupled with synthetic H. halys aggregation pheromones to improve monitoring efforts or could improve the efficacy of modified attract-and-kill control tactics for H. halys.

Limoniic Acid - Major Component of the Sex Pheromones of the Click Beetles Limonius canus and L. californicus.

Wireworms, the larvae of click beetles (Coleoptera: Elateridae), are soil-dwelling insect pests inflicting major economic damage on many types of agricultural crops worldwide. The objective of this work was to identify the female-produced sex pheromones of the Pacific Coast wireworm, Limonius canus LeConte, and the sugarbeet wireworm, L. californicus (Mannerheim) (Coleoptera: Elateridae). Headspace volatiles from separate groups of female L. canus and L. californicus were collected on Porapak Q and analyzed by gas chromatography with electroantennographic detection (GC-EAD) and GC-mass spectrometry. GC-EAD recordings revealed strong responses from male L. canus and male L. californicus antennae to the same compound, which appeared below GC detection threshold. The structure of this candidate pheromone component was deduced from the results of micro-analytical treatments of extracts, retention index calculations on four GC columns, and by syntheses of more than 25 model compounds which were assessed for their GC retention characteristics and electrophysiological activity. The EAD-active compound was identified as (E)-4-ethyloct-4-enoic acid, which we name limoniic acid. In field experiments in British Columbia and Alberta, Canada, traps baited with synthetic limoniic acid captured large numbers of male Limonius click beetles, whereas unbaited control traps captured few. Compared to traps baited with the analogue, (E)-5-ethyloct-4-enoic acid, traps baited with limoniic acid captured 9-times more male L. californicus, and 6.5-times more male western field wireworms, L. infuscatus Motschulsky, but 2.3-times fewer male L. canus. Limoniic acid can now be developed for detection, monitoring and possibly control of L. californicus, L. infuscatus and L. canus populations.

Semiochemical-based Reproductive Isolation Among Sympatric Species of Trypodendron (Coleoptera: Curculionidae: Scolytinae).

Trypodendron retusum (LeConte) (Coleoptera: Curculionidae: Scolytinae) females excised from newly attacked trembling aspen, Populus tremuloides Michaux (Salicaceae), were shown for the first time to produce the aggregation pheromone (+)-lineatin. Coupled gas chromatographic-electroantennographic detection analysis (GC-EAD) disclosed that the antennae of T. retusum, as well as the antennae of three sympatric species, native T. lineatum (Olivier) and T. rufitarsus (Kirby) and exotic T. domesticum (L.), respond to synthetic (+)-lineatin, but not the (-) enantiomer. In contrast, the antennae of T. betulae Swaine responded to SR- and RR-linalool oxide pyranoid and did not detect lineatin. GC-EAD analysis of volatiles from host and nonhost tree species revealed that conifer-produced α-pinene and angiosperm-produced conophthorin and salicylaldehyde were perceived by the antennae of all three native lineatin-perceiving species, suggesting behavioral activity. Field trapping experiments showed that salicylaldehyde synergized the response of coastal, but not interior, T. retusum to lineatin and inhibited the response of T. lineatum and T. rufitarsus. In the absence of salicylaldehyde, α-pinene appeared to inhibit the response of interior T. retusum to lineatin, while for T. lineatum and T. rufitarsus it had an apparent positive additive or synergistic effect. No behavioral response occurred to conophthorin. The results provide evidence for semiochemical-based reproductive isolation between T. retusum and T. betulae, and between these two angiosperm-infesting species and the two conifer-infesting species. They do not explain how isolation could be maintained between T. lineatum and T. rufitarsus.

Brown rats and house mice eavesdrop on each other's volatile sex pheromone components.

Mammalian pheromones often linger in the environment and thus are particularly susceptible to interceptive eavesdropping, commonly understood as a one-way dyadic interaction, where prey sense and respond to the scent of a predator. Here, we tested the "counterespionage" hypothesis that predator and prey co-opt each other's pheromone as a cue to locate prey or evade predation. We worked with wild brown rats (predator of mice) and wild house mice (prey of brown rats) as model species, testing their responses to pheromone-baited traps at infested field sites. The treatment trap in each of two trap pairs per replicate received sex attractant pheromone components (including testosterone) of male mice or male rats, whereas corresponding control traps received only testosterone, a pheromone component shared between mouse and rat males. Trap pairs disseminating male rat pheromone components captured 3.05 times fewer mice than trap pairs disseminating male mouse pheromone components, and no female mice were captured in rat pheromone-baited traps, indicating predator aversion. Indiscriminate captures of rats in trap pairs disseminating male rat or male mouse pheromone components, and fewer captures of rats in male mouse pheromone traps than in (testosterone-only) control traps indicate that rats do eavesdrop on the male mouse sex pheromone but do not exploit the information for mouse prey location. The counterespionage hypothesis is supported by trap catch data of both mice and rats but only the mice data are in keeping with our predictions for motive of the counterespionage.

Identification of Three Monofunctional Diterpene Synthases with Specific Enzyme Activities Expressed during Heartwood Formation in Western Redcedar (Thuja plicata) Trees.

Upon harvest, Western redcedar (WRC; Thuja plicata) trees have a high incidence and extent of heartwood rot. While monoterpenoids and lignans have been linked to rot resistance in this species, other specialized metabolites, such as diterpenes, are likely to contribute to rot resistance. Here we report the cloning and functional assessment of three putative diterpene synthase (TpdiTPS) genes expressed during heartwood formation in WRC. The predicted proteins of the three genes lack either of the two catalytically independent active sites typical of most diTPS, indicating monofunctional rather than bifunctional activity. To identify potential catalytic activities of these proteins, we expressed them in genetically engineered Escherichia coli strains that produce four potential substrates, geranylgeranyl diphosphate (GGDP), ent, syn, and normal stereoisomers of copalyl diphosphate (CDP). We found that TpdiTPS3 used GGDP to produce CDP. TpdiTPS2 used normal CDP to produce levopimaradiene. TpdiTPS1 showed stereoselectivity as it used normal CDP to produce sandaracopimaradiene and syn-CDP to produce syn-stemod-13(17)-ene. These genes and protein enzymatic activities have not been previously reported in WRC and provide an opportunity to assess their potential roles in heartwood rot resistance in this economically important species.

Author Correction: Identification of the Trail Pheromone of the Carpenter Ant Camponotus modoc.

The original version of this article unfortunately contained a mistake.

The fly factor phenomenon is mediated by interkingdom signaling between bacterial symbionts and their blow fly hosts.

We tested the recent hypothesis that the "fly factor" phenomenon (food currently or previously fed on by flies attracts more flies than the same type of food kept inaccessible to flies) is mediated by bacterial symbionts deposited with feces or regurgitated by feeding flies. We allowed laboratory-reared black blow flies, Phormia regina (Meigen), to feed and defecate on bacterial Luria-Bertani medium solidified with agar, and isolated seven morphologically distinct bacterial colonies. We identified these using matrix-assisted laser desorption/ionization mass spectrometry and sequencing of the 16S rRNA gene. In two-choice laboratory experiments, traps baited with cultures of Proteus mirabilis Hauser, Morganella morganii subsp. sibonii Jensen, or Serratia marcescens Bizio, captured significantly more flies than corresponding control jars baited with tryptic soy agar only. A mixture of seven bacterial strains as a trap bait was more attractive to flies than a single bacterial isolate (M. m. sibonii). In a field experiment, traps baited with agar cultures of P. mirabilis and M. m. sibonii in combination captured significantly more flies than traps baited with either bacterial isolate alone or the agar control. As evident by gas chromatography-mass spectrometry, the odor profiles of bacterial isolates differ, which may explain the additive effect of bacteria to the attractiveness of bacterial trap baits. As "generalist bacteria," P. mirabilis and M. m. sibonii growing on animal protein (beef liver) or plant protein (tofu) are similarly effective in attracting flies. Bacteria-derived airborne semiochemicals appear to mediate foraging by flies and to inform their feeding and oviposition decisions.

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.

Identification of the Trail Pheromone of the Carpenter Ant Camponotus modoc.

Trail pheromones deposited by ants lead nestmates to food sources. Based on previous evidence that the trail pheromone of the carpenter ant Camponotus modoc originates from the hindgut, our objective in this study was to identify the key component(s) of the pheromone. We collected C. modoc colonies from conifer forests and maintained them in an outdoor enclosure near our laboratory for chemical analyses and behavioral experiments. In gas chromatographic-electroantennographic detection and gas chromatography-mass spectrometric analyses of worker ant hindgut extracts, we identified five candidate components: 2,4-dimethylhexanoic acid, 2,4-dimethyl-5-hexanolide, pentadecane, dodecanoic acid and 3,4-dihydro-8-hydroxy-3,5,7-trimethylisocoumarin. In a series of trail-following experiments, ants followed trails of synthetic 2,4-dimethyl-5-hexanolide, a blend of the five compounds, and hindgut extract over similar distances, indicating that the hexanolide accounted for the entire behavioral activity of the hindgut extract. The hexanolide not only mediated orientation of C. modoc foragers on trails, it also attracted them over distance, indicating a dual function. Further analyses and bioassays with racemic and stereoselectively synthesized hexanolides revealed that the ants produce, and respond to, the (2S,4R,5S)-stereoisomer. The same stereoisomer is a trail pheromone component in several Camponotus congeners, indicating significant overlap in their respective trail pheromone communication systems.

Isolation, Structure Elucidation, and Total Synthesis of Dolichovespulide, a Sesquiterpene from Dolichovespula Yellowjackets.

As part of an ongoing program to identify sex attractant pheromone components that mediate sexual communication in yellowjacket wasps, a novel sesquiterpene was isolated from body surface extracts of virgin bald-faced hornet queens, Dolichovespula maculata. The gross structure of this sesquiterpene was proposed through microscale spectroscopic analyses, and the configuration of the central olefin was subsequently confirmed by total synthesis. This new natural product (termed here dolichovespulide) represents an important addition to the relatively small number of terpenoids reported from the taxonomic insect family Vespidae.