A Polyketide Male-Produced Aggregation-Sex Pheromone Shared by the North American Cerambycid Beetle Graphisurus fasciatus and the South American Cerambycid Eutrypanus dorsalis.

The longhorn beetle Graphisurus fasciatus (Degeer) ranges from southeastern Canada to Florida and west to Texas, and has frequently been caught during field trials testing attraction of other cerambycid species to their synthesized pheromones. Collections of headspace volatiles from live beetles revealed that males but not females produce a polyketide compound identified as (4R,6S,7E,9E)-4,6,8-trimethylundeca-7,9-dien-3-one ([4R,6S,7E,9E]-graphisurone). Field trials verified that beetles of both sexes were attracted to the synthesized compound, indicating that it is an aggregation-sex pheromone. This structure represents a new structural motif among cerambycid pheromones, and a new natural product. While this study was in progress, the same compound was isolated from males of the South American cerambycid Eutrypanus dorsalis (Germar), in the same subfamily (Lamiinae) and tribe (Acanthocinini) as G. fasciatus. Field trials in Brazil confirmed that (4R,6S,7E,9E)-graphisurone is also an aggregation-sex pheromone for E. dorsalis, and a possible pheromone for two additional sympatric lamiine species, Hylettus seniculus (Germar) (Acanthocinini) and Oreodera quinquetuberculata (Drapiez) (tribe Acrocinini). These results indicate that graphisurone may be shared among a number of related species, as has been found with many components of cerambycid pheromones.

Pheromone Composition and Chemical Ecology of Six Species of Cerambycid Beetles in the Subfamily Lamiinae.

Cerambycid beetles of the subfamily Lamiinae use male-produced aggregation-sex pheromones that are attractive to both sexes. Terpenoid pheromones have been identified from species in the tribes Acanthoderini and Acanthocinini native to North and South America, comprised of (E)-6,10-dimethyl-5,9-undecadien-2-one (geranylacetone), the structurally related 6-methylhept-5-en-2-one (sulcatone), and/or specific enantiomers or nonracemic ratios of enantiomers of the related compounds (E)-6,10-dimethyl-5,9-undecadien-2-ol (fuscumol), its acetate ester, (E)-6,10-dimethyl-5,9-undecadien-2-yl acetate (fuscumol acetate), and 6-methylhept-5-en-2-ol (sulcatol). Here, we present new information about the chemical ecology of six acanthoderine and acanthocinine species native to the eastern USA. The pheromone of Astyleiopus variegatus (Haldeman) previously was identified as a blend of (S)-fuscumol and (S)-fuscumol acetate, and we report here that geranylacetone is a synergistic component. Males of Aegomorphus modestus (Gyllenhal), Lepturges angulatus (LeConte), and Lepturges confluens (Haldeman) were found to produce similar blends composed of the enantiomers of fuscumol acetate and geranylacetone, whereas males of Astylidius parvus (LeConte) and Sternidius alpha (Say) produced both enantiomers of fuscumol together with (R)-fuscumol acetate and geranylacetone. Field experiments with synthesized chemicals revealed that species with similar pheromone composition nevertheless differed in their responses to individual components, and to various blends of components, and in how attraction was influenced by chemicals that were pheromone components of other species. Sulcatone and/or sulcatol antagonized attraction of some species to pheromones of the geranylacetone class, suggesting that there is an adaptive advantage in an ability to detect these heterospecific compounds, such as in avoiding cross attraction to other cerambycid species, as yet unknown, that use pheromones composed of both chemical classes.

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

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.

(2E,6Z,9Z)-2,6,9-Pentadecatrienal as a Male-Produced Aggregation-Sex Pheromone of the Cerambycid Beetle Elaphidion mucronatum.

An increasing body of evidence suggests that the volatile pheromones of cerambycid beetles are much more diverse in structure than previously hypothesized. Here, we describe the identification, synthesis, and field testing of (2E,6Z,9Z)-2,6,9-pentadecatrienal as a male-produced aggregation-sex pheromone of the cerambycid Elaphidion mucronatum (Say) (subfamily Cerambycinae, tribe Elaphidiini). This novel structure is unlike any previously described cerambycid pheromone, and in field bioassays attracted only this species. Males produced about 9 µg of pheromone per 24 h period, and, in field trials, lures loaded with 10, 25, and 100 mg of synthetic pheromone attracted beetles of both sexes, whereas lures loaded with 1 mg of pheromone or less were not significantly attractive. Other typical cerambycine pheromones such as 3-hydroxy-2-hexanone, syn-2,3-hexanediol, and anti-2,3-hexanediol were not attractive to E. mucronatum, and when combined with (2E,6Z,9Z)-2,6,9-pentadecatrienal, the former two compounds appeared to inhibit attraction. Unexpectedly, adults of the cerambycine Xylotrechus colonus (F.) were attracted in significant numbers to a blend of 3-hydroxyhexan-2-one and (2E,6Z,9Z)-2,6,9-pentadecatrienal, even though there is no evidence that this species produces the latter compound. From timed pheromone trap catches, adults of E. mucronatum were determined to be active from dusk until shortly after midnight.

Synergism between Enantiomers Creates Species-Specific Pheromone Blends and Minimizes Cross-Attraction for Two Species of Cerambycid Beetles.

Research over the last decade has revealed extensive parsimony among pheromones within the large insect family Cerambycidae, with males of many species producing the same, or very similar aggregation pheromones. Among some species in the subfamily Cerambycinae, interspecific attraction is minimized by temporal segregation, and/or by minor pheromone components that synergize attraction of conspecifics or inhibit attraction of heterospecifics. Less is known about pheromone-based mechanisms of reproductive isolation among species in the largest subfamily, the Lamiinae. Here, we present evidence that the pheromone systems of two sympatric lamiine species consist of synergistic blends of enantiomers of (E)-6,10-dimethyl-5,9-undecadien-2-ol (fuscumol) and the structurally related (E)-6,10-dimethyl-5,9-undecadien-2-yl acetate (fuscumol acetate), as a mechanism by which species-specific blends of pheromone components can minimize interspecific attraction. Male Astylidius parvus (LeConte) were found to produce (R)- and (S)-fuscumol + (R)-fuscumol acetate + geranylacetone, whereas males of Lepturges angulatus (LeConte) produced (R)- and (S)-fuscumol acetate + geranylacetone. Field experiments confirmed that adult beetles were attracted only by their species-specific blend of the enantiomers of fuscumol and fuscumol acetate, respectively, and not to the individual enantiomers. Because other lamiine species are known to produce single enantiomers or blends of enantiomers of fuscumol and/or fuscumol acetate, synergism between enantiomers, or inhibition by enantiomers, may be a widespread mechanism for forming species-specific pheromone blends in this subfamily.

Cerambycid Beetle Species with Similar Pheromones are Segregated by Phenology and Minor Pheromone Components.

Recent research has shown that volatile sex and aggregation-sex pheromones of many species of cerambycid beetles are highly conserved, with sympatric and synchronic species that are closely related (i.e., congeners), and even more distantly related (different subfamilies), using the same or similar pheromones. Here, we investigated mechanisms by which cross attraction is averted among seven cerambycid species that are native to eastern North America and active as adults in spring: Anelaphus pumilus (Newman), Cyrtophorus verrucosus (Olivier), Euderces pini (Olivier), Neoclytus caprea (Say), and the congeners Phymatodes aereus (Newman), P. amoenus (Say), and P. varius (F.). Males of these species produce (R)-3-hydroxyhexan-2-one as their dominant or sole pheromone component. Our field bioassays support the hypothesis that cross attraction between species is averted or at least minimized by differences among species in seasonal phenology and circadian flight periods of adults, and/or by minor pheromone components that act as synergists for conspecifics and antagonists for heterospecifics.

Seasonal phenology of the cerambycid beetles of east-central Illinois.

We summarize field data on the species composition and seasonal phenology of the community of cerambycid beetles of east-central Illinois. Data were drawn from field bioassays conducted during 2009 - 2012 that tested attraction of adult beetles of diverse species to a variety of synthetic pheromones and host plant volatiles. A total of 34,086 beetles of 114 species were captured, including 48 species in the subfamily Cerambycinae, 41 species in the Lamiinae, 19 species in the Lepturinae, two species in the Spondylidinae, and one species each in the Necydalinae, Parandrinae, Prioninae, and the Disteniidae. Most of the best-represented species were attracted to pheromones that were included in field experiments, particularly species that use (R)-3-hydroxyhexan-2-one as a pheromone component. The species captured, and their patterns of abundance and seasonal phenology were similar to those in an earlier study conducted in Pennsylvania. The most abundant species identified in both studies included the cerambycines Elaphidion mucronatum (Say), Neoclytus a. acuminatus (F.), Neoclytus m. mucronatus (F.), and Xylotrechus colonus (F.). Cerambycine species became active in an orderly progression from early spring through late fall, whereas most lamiine species were active in summer and fall, and lepturine species were limited to summer. Potential cross attraction between some cerambycine species that shared pheromone components may have been averted by differences in seasonal activity period, and by minor pheromone components that acted as synergists for conspecifics and/or antagonists for heterospecifics. These results provide quantitative data on the abundance and seasonal phenology of a large number of species.

Volatiles from male honeydew excretions attract conspecific male spotted lanternflies, Lycorma delicatula (Hemiptera: Fulgoridae).

The spotted lanternfly (SLF), Lycorma delicatula (Hemiptera: Fulgoridae), is a generalist phloem feeder that produces copious amounts of honeydew, which in turn coats the understory. These insects form large aggregations covering the trunks of some trees, while similar trees nearby mysteriously seem unattractive. We investigated whether volatiles from SLF honeydew are attractive to conspecifics by collecting honeydew from the field and testing it for SLF attraction in a two-choice olfactometer. We found that honeydew excreted by adult male SLF was significantly attractive to male SLF, but not female SLF. Although the honeydew excreted by adult female SLF did not significantly attract male or female SLF, both sexes showed a positive trend towards attraction in response to female honeydew in the olfactometer. Analysis of the headspace volatiles of honeydew was conducted, and numerous semiochemicals were identified. Five of which, 2-heptanone, 2-octanone, 2-nonanone, benzyl acetate, and 1-nonanol, were tested in two-choice behavioral assays against a blank control. Benzyl acetate and 2-octanone were attractive to both sexes, whereas 2-heptanone was only attractive to males, and 2-nonanone only to females. The remaining compound, 1-nonanol, repelled females, but not males. Although honeydew has been reported as a source of kairomones for some natural enemies, this may be the first report of sex-specific attractants for conspecific insects found in the honeydew volatiles of a planthopper.

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

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

Evaluation of Methods Used in Testing Attraction of Cerambycid Beetles to Pheromone-Baited Traps.

Here, we describe several field experiments that evaluated potential problems with current methods of trapping cerambycid beetles using panel traps baited with synthesized pheromones. Positioning traps at least 5 m apart in linear transects was effective in preventing unbaited traps from intercepting beetles that were flying to baited traps, which would result in interference between treatments. There was no evidence that traps baited with a strong attractant drew beetles away from traps baited with weaker attractants, which would lead to the erroneous conclusion that the latter have no activity. Unbaited panel traps were minimally attractive to cerambycid beetles, and unlikely to intercept them passively in flight. Finally, dose-response experiments revealed that trap catch of cerambycids was positively associated with pheromone release rates. Overall, our results generally validated current methods of trapping cerambycids using traps baited with pheromones.