Showing papers by "Jocelyn G. Millar published in 2019"

Multi-component blends for trapping native and exotic longhorn beetles at potential points-of-entry and in forests

Abstract: The accidental introduction of exotic wood-boring cerambycid beetles represents an ever-increasing threat to forest biosecurity and the economies of many countries. Early detection of such species upon arrival at potential points-of-entry is challenging. Because pheromone components are often conserved among related species in the family Cerambycidae, we tested the generic attractiveness of different blends of pheromones composed of increasing numbers of pheromone components at both potential points-of-entry and in natural forests in France during 2014–2017. Initially, two different four-component blends were compared, one composed of fuscumol, fuscumol acetate, geranylacetone, and monochamol, and the other composed of 3-hydroxyhexan-2-one, anti-2,3-hexanediol, 2-methylbutanol, and prionic acid. In a second step, host volatiles (ethanol and [-]-α-pinene) were added, and finally, we tested the effectiveness of a mixture of all eight pheromone components with the two host volatiles. Overall, 13,153 cerambycid beetles of 118 species were trapped. The 114 native species trapped represent 48% of the French fauna, including more than 50% of the species in 25 of the 41 cerambycid tribes. At potential points-of-entry, captures included 2960 cerambycids of 49 species, including three exotic Asian species, two of which had never been reported previously in Europe. In forests, attraction to the four-component blends varied with their composition. Adding host volatiles did not change the overall attraction except for the species Phymatodes testaceus, which showed a fourfold increase in captures. Placing the two four-component blends on the same trap resulted in significant increases in the number of species and individuals captured compared to captures by traps baited with each blend individually. Finally, the eight-component pheromone blend was found to be as attractive as the combination of the two four-component blends hung together on the same trap, without apparent antagonistic effects. This finding suggests that use of multi-component lures may help to minimize the costs and manpower required to detect exotic and potentially invasive species.

Honeybees possess a structurally diverse and functionally redundant set of queen pheromones.

Abstract: Queen pheromones, which signal the presence of a fertile queen and induce workers to remain sterile, play a key role in regulating reproductive division of labour in insect societies. In the honeybee, volatiles produced by the queen's mandibular glands have been argued to act as the primary sterility-inducing pheromones. This contrasts with evidence from other groups of social insects, where specific queen-characteristic hydrocarbons present on the cuticle act as conserved queen signals. This led us to hypothesize that honeybee queens might also employ cuticular pheromones to stop workers from reproducing. Here, we support this hypothesis with the results of bioassays with synthetic blends of queen-characteristic alkenes, esters and carboxylic acids. We show that all these compound classes suppress worker ovary development, and that one of the blends of esters that we used was as effective as the queen mandibular pheromone (QMP) mix. Furthermore, we demonstrate that the two main QMP compounds 9-ODA and 9-HDA tested individually were as effective as the blend of all four major QMP compounds, suggesting considerable signal redundancy. Possible adaptive reasons for the observed complexity of the honeybee queen signal mix are discussed.

Do Primitively Eusocial Wasps Use Queen Pheromones to Regulate Reproduction? A Case Study of the Paper Wasp Polistes satan

Abstract: In several highly eusocial insect species with morphologically distinct castes, queen-characteristic cuticular hydrocarbons (CHCs) have been shown to act as queen signals that suppress the reproduction of nestmate workers. However, it is not known whether such queen pheromones might also play a role in regulating reproductive division of labour in primitively eusocial insects that lack morphologically defined castes. Here, we experimentally tested whether a blend of CHCs which occurred in higher concentrations in the dominant breeding female act as a queen pheromone, and inhibit reproduction by subordinate females in the primitively eusocial paper wasp Polistes satan. In contrast to earlier findings with highly eusocial species, our results show that although specific compounds were enhanced in dominant, reproductively active females, a blend of five of these compounds did not inhibit development of the ovaries of female nestmates. Instead, the dominant female had to be physically present to prevent subordinate females from reproducing. Our results are in line with earlier evidence suggesting that fertility-linked compounds in primitively eusocial wasps act only as cues and help to regulate reproduction when used in conjunction with aggressive dominance behaviour, meaning the physical presence of the dominant female. Alternatively, our results support the hypothesis that queen pheromones in highly eusocial insects were co-opted from fertility cues that were already present in primitively eusocial ancestors, even when initially, such compounds were merely produced as by-products of ovarian activation, without actually serving to signal reproductive status.

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

Abstract: 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.

Pheromone identification by proxy: identification of aggregation-sex pheromones of North American cerambycid beetles as a strategy to identify pheromones of invasive Asian congeners

Abstract: Research over the past decade has shown that attractant pheromones used by cerambycid beetles are often highly conserved, with the same compound being used as a pheromone component by multiple related species, even among species on different continents which have been separated for millions of years. We describe how this conservation of structures can be exploited to identify possible pheromone components for Asian target species with a high risk of invading North America. Thus, collection and analysis of volatiles from five North American species, Semanotus amethystinus (LeConte), Semanotus ligneus (F.), Semanotus litigiosus (Casey), Callidium antennatum hesperum Casey, and Callidium pseudotsugae Fisher, showed that males of the two Callidium species sex-specifically produced 3-hydroxyhexan-2-one, a previously known cerambycid pheromone component, along with a novel natural product, 1-(1H-pyrrol-2-yl)-1,2-propanedione (henceforth pyrrole). In contrast, males of the three Semanotus species produced only the pyrrole. In field bioassays, both sexes of C. antennatum hesperum were significantly attracted to the blend of the two compounds, and S. amethystinus were equally attracted to the pyrrole alone, or the blend of the two compounds. Even before completing field bioassays with these species in California, field testing of the two compounds in Japan and China had revealed that several related target species, including the invasive Callidiellum rufipenne (Motschulsky), Callidiellum villosulum (Fairmaire), and Semanotus bifasciatus (Motschulsky), were attracted to one or both compounds (data reported elsewhere), providing proof of concept of the “pheromone identification by proxy” strategy.

13-Tetradecenyl acetate, a female-produced sex pheromone component of the economically important click beetle Melanotus communis (Gyllenhal) (Coleoptera: Elateridae).

Abstract: Species-specific behavior-modifying chemicals have been used for more than 50 years for monitoring and management of insect pests of agriculture and human health. Elaterid beetle larvae are among insect pests in soil that are increasingly problematic, in part due to the lack of effective management strategies. However, little is known about the insect-produced chemicals that mediate the reproductive behavior of these pests. We used chemical and behavioral studies to identify, synthesize, and field test the sex attractant pheromone of adults of Melanotus communis, commonly called the corn wireworm, the larvae of which are economically important pests of U.S. crops. Our results indicated that a single female-produced chemical, 13-tetradecenyl acetate, was strongly attractive to conspecific male beetles, and did not appear to attract other species. In field evaluations, male M. communis exhibited a dose-dependent response to this compound. In a trial comparing different slow-release dispensers, a small rubber septum impregnated with the chemical was as effective as and easier to use than a plastic bag dispenser. Given that the sex attractant of this insect consists of a single compound that can be readily synthesized, its development for monitoring and management of the corn wireworm may be economically feasible.

( S )-Sulcatol Is a Pheromone Component for Two Species of Cerambycid Beetles in the Subfamily Lamiinae

Abstract: Males of several species in the large cerambycid beetle subfamily Lamiine, native to South and North America, are known to produce aggregation-sex pheromones composed of three related structures: the sesquiterpene catabolic product geranylacetone, its corresponding alcohol (known as fuscumol), and the acetate ester of the alcohol (fuscumol acetate). Here, we show that males of two lamiine species native to the eastern USA, Astylopsis macula (Say) and Leptostylus transversus (Gyllenhal) (both tribe Acanthocinini), produce pheromones composed of the structurally related (S)-6-methylhept-5-en-2-ol ([S]-sulcatol). Males of both species also produced 6-methylhept-5-en-2-one (sulcatone), and males of A. macula produced trace amounts of (R)-fuscumol acetate. Field experiments demonstrated that both species were attracted by (S)-sulcatol. Sulcatone was not attractive as a single component, nor did it influence attraction of A. macula to (S)-sulcatol, while its effect on L. transversus was unclear. Data from the field experiments, and a separate experiment using traps fitted with a timer mechanism that rotated trap jars, revealed that the two species overlap only slightly in both seasonal and daily flight period, thus minimizing interspecific attraction. Racemic fuscumol acetate and fuscumol antagonized attraction of both species to sulcatol. The identification of sulcatol as a cerambycid pheromone extends the known range of pheromone components in the subfamily Lamiinae.

Isolation and identification of a male-produced aggregation-sex pheromone for the velvet longhorned beetle, Trichoferus campestris

Abstract: The velvet longhorned beetle, Trichoferus campestris (Faldermann) ("VLB"; Coleoptera: Cerambycidae), is native to eastern Asia where it infests and damages a wide range of deciduous and coniferous tree species, including orchard and timber species. Immature stages of VLB are transported to new countries via international commerce, and populations have established outside the native range of the species. Here, we show that identification of pheromones of invasive pest species can be expedited by knowledge of the semiochemistry of related taxa. Histological sectioning revealed subcuticular, male-specific prothoracic glands connected to pits in the cuticle, which, in related species, are diagnostic for production of male-produced aggregation-sex pheromones, usually characterized by 2,3-alkanediol/hydroxyketone structural motifs. However, in preliminary field bioassays, beetles were not attracted by any known cerambycid pheromones. Subsequently, we identified a novel variant of the hydroxyketone motif ("trichoferone") from headspace volatiles of males. In field bioassays, synthetic trichoferone was more attractive to both sexes of VLB than previously developed high-release-rate ethanol lures, and attraction was strongly female biased. This study demonstrated the utility of the prothoracic gland trait for predicting pheromone use in cerambycid species in the subfamily Cerambycinae, and that identification of pheromones of novel species can be expedited by knowledge of pheromones of related species. Trichoferone should prove to be a valuable tool for detection of VLB in regions where the beetle is or may become established.

The Male-Produced Aggregation-Sex Pheromone of the Cerambycid Beetle Plagionotus detritus ssp. detritus

Abstract: The number of longhorn beetles with confirmed aggregation-sex pheromones has increased rapidly in recent years. However, the species that have been studied most intensively are pests, whereas much less is known about the pheromones of longhorn beetles that are rare or threatened. We studied the cerambycid beetle Plagionotus detritus ssp. detritus with the goal of confirming the presence and composition of an aggregation-sex pheromone. This species has suffered widespread population decline due to habitat loss in Western Europe, and it is now considered threatened and near extinction in several countries. Beetles from a captive breeding program in Sweden were used for headspace sampling. Gas chromatography-mass spectrometry revealed that collections from males contained large quantities of two compounds, identified as (R)-3-hydroxy-2-hexanone (major component) and (S)-2-hydroxy-3-octanone (minor component), in addition to smaller quantities of 2,3-hexanedione and 2,3-octanedione. None of the compounds was present in collections from females. When tested singly in a field bioassay, racemic 3-hydroxy-2-hexanone and 2-hydroxy-3-octanone were not attractive to P. detritus, whereas a 5:1 blend elicited significant attraction. Both compounds are known as components of the pheromones of conspecific beetles, but, to our knowledge, this is the first cerambycid shown to use two compounds with different chain lengths, in which the positions of the hydroxyl and carbonyl functions are interchanged between the two. The pheromone has potential as an efficient tool to detect and monitor populations of P. detritus, and may also be useful in more complex studies on the ecology and conservation requirements of this species.

Optimizing pheromone-based lures for the invasive red-necked longhorn beetle, Aromia bungii

Abstract: Aromia bungii is a serious pest of stone fruit trees including cherries, plums, peaches and apricots. It is native to eastern Asia but has recently been introduced into and has established in Japan, Germany and Italy and has been intercepted in cargo entering the USA and Great Britain. We synthesized the naturally produced enantiomer of the major pheromone component, (E)-2-cis-6,7-epoxynonenal, and in field tests, comparing its attractiveness to that of the racemate. We also tested different ratios of a minor pheromone component, (2E,6Z)-nona-2,6-dienal, on attraction to the major component. Lastly, we conducted a dose–response assay to determine the optimal loading rates. Addition of the minor component at a ratio of 0.31 mg minor to 25 mg major component is more than double the trap captures of males but not females. Using this ratio, we found no difference in trap captures with 10 mg, 32 mg or 100 mg of the major component, but the 10 mg load attracted significantly more females than the 3.2 mg load, and only the 32 mg load attracted significantly more males than the 3.2 mg load. The natural enantiomer was significantly more attractive to females than the racemate. However, the multi-step, low-yielding synthesis likely will prohibit the insect-produced enantiomer from being used for operational trapping. The addition of the minor component to the racemate significantly increased trap catches, and the dose–response assay did not indicate significant differences in loads above 10 mg of the racemic major component when formulated with ~ 1.2% of the minor component.

Evidence of Aggregation-Sex Pheromone Use by Longhorned Beetles (Coleoptera: Cerambycidae) Species Native to Africa.

Abstract: During field bioassays in Kenya of 10 chemicals that are common pheromone components of cerambycid beetles, six species in the subfamily Cerambycinae were significantly attracted to 3-hydroxyhexan-2-one, and one species in the subfamily Lamiinae was significantly attracted to 2-(undecyloxy)ethanol (known as monochamol). These results further demonstrate that the former compound is highly conserved as a cerambycid pheromone because it has now been identified or implicated in the pheromones of numerous cerambycine species native to all six habitable continents. Similarly, monochamol has been identified or implicated as a pheromone component for species in the subfamily Lamiinae native to Asia, Europe, North America, and now Africa. The eight other compounds tested, including (E)-6,10-dimethyl-5,9-undecadien-2-ol (fuscumol), the corresponding (E)-6,10-dimethyl-5,9-undecadien-2-yl acetate (fuscumol acetate), syn- and anti-(2,3)-hexanediols and (2,3)-octanediols, 3-hydroxyoctan-2-one, and 3-hydroxydecan-2-one, did not attract significant numbers of any species.

Common Cerambycid Pheromone Components as Attractants for Longhorn Beetles (Cerambycidae) Breeding in Ephemeral Oak Substrates in Northern Europe

Abstract: Longhorn beetles are ecologically important insects in forest ecosystems as decomposers of woody substrates, microhabitat engineers, and as components of forest food webs. These species can be greatly affected both positively and negatively by modern forestry management practices, and should be monitored accordingly. Through headspace sampling, coupled gas chromatography-electroantennography, gas chromatography-mass spectrometry, and field bioassays, we identified two compounds, 2-methyl-1-butanol and 3-hydroxy-2-hexanone, that constitute aggregation-sex pheromone attractants of three cerambycid species which breed primarily in different types of fresh, recently dead oak wood in Northern Europe: Pyrrhidium sanguineum (L.), Phymatodes alni ssp. alni (L.), and Phymatodes testaceus (L.) (Cerambycinae: Callidiini). Analyses of headspace volatiles collected from live insects indicated that the male-produced aggregation-sex pheromone of P. sanguineum is a 1–15:100 blend of (R)-2-methyl-1-butanol and (R)-3-hydroxy-2-hexanone, whereas the corresponding ratios for P. alni were 70–110:100. In field bioassays, adult P. sanguineum and P. alni were significantly attracted to multiple blends with varying ratios of the two compounds. When tested individually, the compounds were minimally attractive. In contrast, adult P. testaceus exhibited nonspecific attraction to both of the individual compounds and to different blends, despite the hydroxyketone not being part of its pheromone, which consists of (R)-2-methyl-1-butanol alone. Overall, our results suggest that a blend of 50:100 of racemic 2-methyl-1-butanol and 3-hydroxy-2-hexanone is appropriate for parallel, cost-efficient pheromone-based monitoring of all three species. In particular, these species could serve as useful indicators of how modern forestry practices affect a whole guild of saproxylic insects that require ephemeral deadwood substrates for successful breeding.

The aggregation-sex pheromones of the cerambycid beetles Anaglyptus mysticus and Xylotrechus antilope ssp. antilope: new model species for insect conservation through pheromone-based monitoring

Abstract: We studied the pheromone chemistry of the cerambycids Anaglyptus mysticus and Xylotrechus antilope ssp. antilope with the goal of identifying attractants that could be used as tools for pheromone-based monitoring of these two species, which are rare and red-listed in parts of northern Europe. Beetles were reared from naturally colonized branches of hazel (Corylus avellana) or oak (Quercus robur), respectively, and used for headspace sampling. The extracts of volatiles were analyzed by gas chromatography–mass spectrometry. Males of A. mysticus consistently produced large quantities of (R)-3-hydroxy-2-hexanone and 2-nonanone, minor amounts of 2,3-hexanedione, and trace amounts of six other compounds. The average proportion of 2-nonanone to (R)-3-hydroxy-2-hexanone was 70:100. Males of X. antilope produced large quantities of (S)-2-hydroxy-3-octanone, and minor quantities of 2,3-octanedione. None of these compounds were present in the corresponding extracts of females from either species. The attractiveness of the dominant compounds produced by each species was determined in field bioassays. Lures with racemic 3-hydroxy-2-hexanone and 2-nonanone as single compounds were not attractive to A. mysticus. However, the compounds acted synergistically in blends of 100:100 and 160:100 of 2-nonanone to the hydroxyketone’s (R)-enantiomer, but not in a 40:100 blend. Similarly (S)-2-hydroxy-3-octanone and its racemate attracted significantly more X. antilope than controls. Males and females of both species were captured in approximately equal numbers. The aggregation-sex pheromones of A. mysticus and X.antilope have high potential to serve as sensitive and efficient tools for detection and monitoring of local populations, and in studies of the species’ ecology and conservation requirements.

A male-produced aggregation-sex pheromone of the beetle Arhopalus rusticus (Coleoptera: Cerambycidae, Spondylinae) may be useful in managing this invasive species.

Abstract: The longhorned beetle Arhopalus rusticus (Coleoptera: Cerambycidae, Spondylinae) is a common species in conifer forests of the Northern Hemisphere, but with global trade, it has invaded and become established in New Zealand, Australia, and South America. Arhopalus rusticus is a suspected vector of the phytopathogenic nematode, Bursaphelenchus xylophilus, the causative agent of pine wilt disease, which is a major threat to pine forests worldwide. Here, we report the identification of a volatile, male-produced aggregation-sex pheromone for this species. Headspace odours from males contained a major male-specific compound, identified as (2 S, 5E)-6,10-dimethyl-5,9-undecadien-2-ol (common name (S)-fuscumol), and a minor component (E)-6,10-dimethyl-5,9-undecadien-2-one (geranylacetone). Both compounds are known pheromone components for species in the same subfamily. In field trials in its native range in Slovenia, (S)-fuscumol was significantly more attractive to beetles of both sexes, than racemic fuscumol and a blend of host plant volatiles commonly used as an attractant for this species. Fuscumol-baited traps also caught significant numbers of another spondylidine species, Spondylis buprestoides (L.), and a rare click beetle, Stenagostus rufus (De Geer). The pheromone can be exploited as a cost-effective and environmentally safe tool for detection and monitoring of this invasive species at ports of entry, and for monitoring the beetle’s distribution and population trends in both endemic and invasive populations.

Enantiomers of fuscumol acetate comprise the aggregation‐sex pheromone of the South American cerambycid beetle Psapharochrus maculatissimus, and likely pheromones of the cerambycids Eupromerella plaumanni and Hylettus seniculus

Abstract: There is increasing evidence that pheromone chemistry within the large coleopteran family Cerambycidae is often highly conserved, with numerous related species sharing the same pheromone components. As a result, traps containing these components can attract multiple cerambycid species simultaneously. In the present study, we exploited this concept in the identification of the male‐produced aggregation‐sex pheromone of the South American species Psapharochrus maculatissimus (Bates) (Coleoptera: Cerambycidae, subfamily Lamiinae, tribe Acanthoderini). Initially, live adults of both sexes were caught using a trap baited with a lure containing a blend of known cerambycid pheromone components. Headspace volatiles were collected from live beetles and analyzed by coupled gas chromatography‐mass spectrometry. Males of P. maculatissimus sex‐specifically produced a 1:38 blend of (R)‐fuscumol acetate ([2R,5E]‐6,10‐dimethylundeca‐5,9‐dien‐2‐yl acetate) and (S)‐fuscumol acetate, which were both components of the pheromone lures to which they had been attracted. In more focused field trials, traps baited with the (S)‐enantiomer, or a blend approximating the natural 1:38 ratio of (R)‐ to (S)‐enantiomers, attracted adults of both sexes in approximately equal numbers. During bioassays, adults of the lamiine species Eupromerella plaumanni (Fuchs) (tribe Acanthoderini) and Hylettus seniculus (Germar) (Acanthocinini) also were attracted, but to different lures, with E. plaumanni being attracted to the racemic mixture of the two enantiomers of fuscumol acetate, whereas H. seniculus was attracted specifically to (R)‐fuscumol acetate. Our results suggest that differences between these sympatric species in the stereochemistry of fuscumol acetate impart species‐specificity to pheromone communication channels, similar to what has been found recently with lamiine species from other continents.

A pleiotropic chemoreceptor facilitates the coupling of pheromonal signal perception and production

Abstract: Optimal mating decisions depend on reliable and precise species-specific coupling of the production and perception of mating communication signals because any functional changes in either the signal or its perception should carry a fitness cost (Boake, 1991; Brooks et al., 2005; Hoy et al., 1977b; Shaw et al., 2011; Shaw and Lesnick, 2009; Steiger et al., 2010; Sweigart, 2010; Symonds and Elgar, 2008; Wyatt and Cambridge University Press, 2014). Previously published theoretical models predict that genetic linkage between sensory-driven mate choices and specific communication signals could provide a robust mechanism for maintaining robust and stable signal production and perception at the level of populations, while still retaining the capacity for future signal diversification (Hoy et al., 1977b; Shaw et al., 2011; Shaw and Lesnick, 2009; Wiley et al., 2011). Several experimental studies have provided empirical evidence that pleiotropy is one possible genetic solution for maintaining functional coupling between specific communication signals and the mate choice behaviors they elicit at the population level (Hoy et al., 1977b; Shaw et al., 2011; Shaw and Lesnick, 2009; Wiley et al., 2011). However, the complex characteristics of mating signals and behaviors present a major barrier for identifying the actual pleiotropic genes and molecular pathways that provide genetic linkages between the production and perception of mating signals (Chenoweth and Blows, 2006; Singh and Shaw, 2012). Here we show that in the fruit fly Drosophila melanogaster, some pheromone-driven mating choices are coupled to the production of specific mating signals via pleiotropic chemoreceptors. Specifically, we demonstrate that Gr8a, a member of the gustatory receptor family, independently contributes to the perception of inhibitory mating signals in pheromone sensing neurons, as well as in regulating the production of inhibitory mating signals in oenocytes. Together, these data provide a relatively simple molecular explanation for how coupling of pheromone perception and production, two independent physiological processes, remains robust.

An Unstable Monoterpene Alcohol as a Pheromone Component of the Longhorned Beetle Paranoplium gracile (Coleoptera: Cerambycidae)

Abstract: We report the identification of p-mentha-1,3-dien-8-ol, an unstable monoterpene alcohol, as a male-produced aggregation-sex pheromone component of the cerambycid beetle Paranoplium gracile (Leconte) (subfamily Cerambycinae, tribe Oemini), a species endemic to California. Headspace volatiles from live males contained a blend of nine cyclic terpenoids that were not detected in analogous samples from females. Volatiles produced by male Eudistenia costipennis Fall, also in the tribe Oemini, contained the same suite of nine compounds. Four compounds, dehydro-p-cymene, p-mentha-1,3-dien-8-ol, p,α,α-trimethylbenzyl alcohol, and an unidentified compound were found to elicit responses from antennae of P. gracile females in coupled gas chromatography-electroantennogram detection (GC-EAD) assays, whereas only p-mentha-1,3-dien-8-ol elicited responses from antennae of males. In field assays, p-mentha-1,3-dien-8-ol stabilized with the antioxidant butylated hydroxytoluene (BHT) attracted P. gracile of both sexes, indicating it functions as an aggregation-sex pheromone, as with other pheromones identified from its subfamily, the Cerambycinae. Adding four of the other compounds found in headspace samples to the dienol lure had no effect on attraction. Because of the instability of p-mentha-1,3-dien-8-ol, it seems likely that at least some of the compounds seen in the extracts of volatiles from both species are artefacts, rather than being components of the pheromone.

Identification of the aggregation-sex pheromone of Plagionotus arcuatus ssp. arcuatus (Coleoptera: Cerambycidae) from two geographically separated European populations

Abstract: Plagionotus arcuatus ssp. arcuatus (L.) is a common saproxylic cerambycid beetle in most parts of Europe, and is designated as an occasional pest of oak wood that is stored outside during the summer months. In an effort to identify attractants that can be used for monitoring this species, we collected headspace samples from adult beetles and conducted field bioassays with the resulting compounds as potential aggregation-sex pheromone components for this species. Three compounds, (R)-3-hydroxyhexan-2-one, (R)-3-hydroxyoctan-2-one, and (R)-3-hydroxydecan-2-one, were consistently present in relatively large quantities in headspace extracts from male P. arcuatus populations in both Hungary and Sweden, regardless of the adsorbent media (activated charcoal or Porapak™ Q) used to sample beetle odors, or the type of solvent (hexane, diethyl ether, or dichloromethane) used to elute trapped volatiles from the collectors. None of the hydroxyketone and related compounds were detected in corresponding extracts from females. In field bioassays in both countries, the blend of the C6 and C10 compounds, and the ternary blend both attracted significantly more beetles than the control, while other combinations or single compounds were not significantly attractive. Males and females showed similar patterns of responses to treatments. Our results demonstrate that (R)-3-hydroxyhexan-2-one and (R)-3-hydroxydecan-2-one constitute a male-produced aggregation-sex pheromone of P. arcuatus, whereas the role of (R)-3-hydroxyoctan-2-one remains unclear. Lures with the pheromone could be developed for monitoring of P. arcuatus populations as an indicator of fresh oak wood resources.

Effects of Pheromone Dose and Conspecific Density on the Use of Aggregation-Sex Pheromones by the Longhorn Beetle Phymatodes grandis and Sympatric Species (Coleoptera: Cerambycidae).

Abstract: Many species of longhorn beetles (Coleoptera: Cerambycidae) utilize male-produced aggregation-sex pheromones that attract both sexes. However, the reasons why and the details of how this type of pheromone is used by cerambycids and other coleopteran species that utilize analogous male-produced pheromones remain unclear. Thus, our goals were to test the hypotheses that 1) cerambycids respond to pheromones in a dose-dependent (= release rate-dependent) manner and 2) pheromone emission is density-dependent. If true, these characteristics of pheromone use could suggest that cerambycids utilize an optimal density strategy to limit competition for scarce and ephemeral hosts, i.e., the stressed or dying trees that typically constitute their larval hosts. Attraction of beetles to a range of release rates of two common pheromone components – 2-methylbutanol and 3-hydroxyhexan-2-one – was tested in field trials. Responses, as measured by the number of beetles caught in pheromone-baited traps, increased with release rates for five endemic species, even at the highest rates tested (~1450 μg/h for 2-methylbutanol and ~720 μg/h for 3-hydroxyhexan-2-one). The effect of density of conspecific males on per capita pheromone production was tested by collecting the volatiles produced by individuals, pairs, or groups of three or four male Phymatodes grandis Casey. Frequency of pheromone production was significantly different among the treatment densities, and emission rates of the pheromone (R)-2-methylbutanol decreased with increasing density. These results are discussed in the context of a possible optimal density strategy used by cerambycids, and more broadly, in relation to the use of male-produced aggregation-sex pheromones by other coleopterans. In addition, we report the identification of the pheromones of four of our five test species, specifically, Phymatodes obliquus Casey, Brothylus conspersus LeConte, Brothylus gemmulatus LeConte, and Xylotrechus albonotatus Casey.

A new synthetic lure for management of the invasive giant African snail, Lissachatina fulica.

Abstract: Synthetic chemical lures mimicking pheromones or food attractants are essential tools in eradication programs for invasive species. However, their uses in programs aiming to control or eradicate terrestrial gastropods are largely unexplored. The goal of this study was to find a synthetic attractant that could aid in the eradication or management of the giant African snail (Lissachatina fulica). Field studies in Hawaii showed that a commercial papaya-flavored oil attracted snails. Analysis of the odor profile of the oil identified a total of 22 chemicals, which comprised > 98% of the volatile compounds emitted by the oil. A synthetic blend was reconstructed that mirrored the release rates of the papaya oil odors. In laboratory and field bioassays, the reconstructed blend, applied to cotton wicks as water and canola oil or water and mineral emulsions, attracted more snails than the water and oil emulsion control wicks. Field studies in Hawaii and Florida showed that the reconstructed blend in an oil emulsion was not attractive to non-target species such as butterflies or bees. The snails were attracted from distances > 1 m and entered traps baited with the attractant emulsion. When tested in the South Florida giant African snail eradication program, direct ground application of the reconstructed papaya-flavored oil emulsion increased the number of snails killed by over 87% compared to water emulsion controls. Integrating tactics using the synthetic papaya oil attractant into control measures should increase the effectiveness of eradication and management programs.

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

Abstract: 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.

Response of Invasive Longhorn Beetles (Coleoptera: Lamiinae) to Known Cerambycid Aggregation-Sex Pheromones in the Puna District of Hawaii Island

Abstract: The Queensland longhorn borer (QLB; Acalolepta aesthetica [Olliff 1890]; Coleoptera: Cerambycidae: Lamiinae: Monochamini) and plumeria longhorn borer (PLB; Lagocheirus obsoletus [Thomson 1778] = Lagocheirus undatus [Voet 1778]; Coleoptera: Cerambycidae: Lamiinae: Acanthocini) are invasive longhorn beetle species that have become established on the island of Hawaii. Both QLB and PLB are polyphagous. Known hosts of QLB include cacao, citrus, kukui, and breadfruit in Hawaii, and QLB are known to attack live, healthy trees. Currently the beetle occurs in the Puna district of the island, but its range is expanding. PLB is a pest of plumeria and other ornamental plants throughout the state of Hawaii and elsewhere. As a first step towards developing a monitoring tool for these invasive beetles, we tested four known aggregation-sex pheromones of cerambycids in this subfamily—monochamol, fuscumol acetate, fuscumol, and geranylacetone—that have proven effective for attracting more than 30 lamiine species in different areas of the world. When tested in panel traps, these compounds individually and in a blend attracted 9 QLB total, which was not significantly different than the 5 QLB captured in solvent control traps. In contrast, traps baited with one of the tested compounds, fuscumol acetate, captured significantly more PLB than solvent blank control traps. We discuss future research directions for developing attractants using chemical ecology approaches to monitor QLB and PLB.