Sex Pheromone of the Click Beetle Agriotes pilosellus (SCHöNHERR, 1718).

Agriotes pilosellus is a fairly common click beetle species distributed in open deciduous and mixed forests throughout a large area in Europe. To identify its sex pheromone, gland extracts of female beetles were analyzed using gas chromatography-mass spectrometry (GC-MS). The only volatile compounds present in the extracts were geranyl butanoate and (E)-8-hydroxygeranyl dibutanoate in a 1:3 ratio, identified by comparison with synthetic samples. Field experiments revealed a clear attraction of A. pilosellus - males towards traps baited with geranyl butanoate, which could be synergistically enhanced by the factor of almost ten by addition of (E)-8-hydroxygeranyl dibutanoate. The latter compound alone did not show any attractive effect. Both compounds correspond well to the structures known from other Agriotes species and may serve as an effective monitoring tool for entomofaunistic research.

Floral Scents of a Deceptive Plant Are Hyperdiverse and Under Population-Specific Phenotypic Selection.

Floral scent is a key mediator in plant-pollinator interactions. However, little is known to what extent intraspecific scent variation is shaped by phenotypic selection, with no information yet in deceptive plants. In this study, we collected inflorescence scent and fruit set of the deceptive moth fly-pollinated Arum maculatum L. (Araceae) from six populations north vs. five populations south of the Alps, accumulating to 233 samples in total, and tested for differences in scent, fruit set, and phenotypic selection on scent across this geographic barrier. We recorded 289 scent compounds, the highest number so far reported in a single plant species. Most of the compounds occurred both north and south of the Alps; however, plants of the different regions emitted different absolute and relative amounts of scent. Fruit set was higher north than south of the Alps, and some, but not all differences in scent could be explained by differential phenotypic selection in northern vs. southern populations. This study is the first to provide evidence that floral scents of a deceptive plant are under phenotypic selection and that phenotypic selection is involved in shaping geographic patterns of floral scent in such plants. The hyperdiverse scent of A. maculatum might result from the imitation of various brood substrates of its pollinators.

Sex Pheromone of the Rare Click Beetle Betarmon bisbimaculatus.

The click beetle Betarmon bisbimaculatus (Fabricius, 1803) (Coleoptera: Elateridae) has a scattered distribution throughout a large area in Europe and the near East. Due to its scarcity, little is known about the ecology, biology, and development of this peculiar species. Here, we studied the composition of the female-released sex pheromone of B. bisbimaculatus. Neryl hexanoate, neryl octanoate, and neryl decanoate, in a ratio of approximately 3:1:6, were the only volatile compounds present in the extracts of pheromone glands. A synthetic mixture of all three compounds in the natural ratio was highly attractive to males in field traps. When the compounds were tested individually, only traps baited with neryl hexanoate were attractive, but they caught only a sixth of the males compared to the mixture. Based on the similarity of their sex pheromones, we propose that the tribe Pomachiliini with B. bisbimaculatus is closely related to the tribe Agriotini. This study shows the potential of sex pheromone studies for monitoring of rare and threatened insects as well as for elucidating phylogenetic relationships.

Decrypting Cryptic Click Beetle Species by Analysis of Sex Pheromones.

Despite sex pheromones being highly species specific, their use as phylogenetic characters and a tool for the verification of species status are still relatively few compared to use of morphological and molecular characters. Earlier studies revealed that within the click beetle species Idolus picipennis, two types can be separated based on pheromone composition. Gas chromatography/mass spectrometry analysis of pheromone from a third type of Idolus revealed the presence of geranyl hexanoate and geranyl octanoate in a ratio of ca. 1:9. Neryl esters and farnesyl esters, present in the glands of the other two species, are absent in this type. In field experiments, males of all three types were attracted specifically to synthetic mixtures of pheromone resembling their own females. This suggests that cross attraction among different types is unlikely and indicates that they are likely distinct species. Using the large numbers of male beetles caught in pheromone traps, morphological differences between the species were studied and an identification key derived. This study highlights the role of sex pheromones as a powerful tool in integrative taxonomy and systematics to study the phylogenetic position and evolution of taxa and to determine the taxonomic status of cryptic species.

Pheromonal Communication in the European House Dust Mite, Dermatophagoides pteronyssinus.

Despite the sanitary importance of the European house dust mite Dermatophagoides pteronyssinus (Trouessart, 1897), the pheromonal communication in this species has not been sufficiently studied. Headspace analysis using solid phase micro extraction (SPME) revealed that nerol, neryl formate, pentadecane, (6Z,9Z)-6,9-heptadecadiene, and (Z)-8-heptadecene are released by both sexes whereas neryl propionate was released by males only. Tritonymphs did not produce any detectable volatiles. In olfactometer experiments, pentadecane and neryl propionate were attractive to both sexes as well as to tritonymphs. (Z)-8-heptadecene was only attractive to male mites. Therefore it is discussed that pentadecane and neryl propionate are aggregation pheromones and (Z)-8-heptadecene is a sexual pheromone of the European house dust mite D. pteronyssinus. To study the potential use of pheromones in dust mite control, long-range olfactometer experiments were conducted showing that mites can be attracted to neryl propionate over distances of at least 50 cm. This indicates that mite pheromones might be useable to monitor the presence or absence of mites in the context of control strategies.

Identification of the sex pheromone of Idolus picipennis (Bach, 1852) revealed the presence of a cryptic sibling species.

The click beetle Idolus picipennis represents the only species of its genus in Europe, where it is widely distributed but is rare and only occurs locally. In order to identify its sex pheromone we investigated gland extracts of females from populations in southern Germany. GC/MS analyses revealed two distinct types of gland compositions that correspond to slight but consistent morphological differences in the respective beetles. Extracts of one type contain four compounds, geranyl hexanoate (~ 40 %), (Z,E)-farnesyl hexanoate (~ 10 %), (E,E)-farnesyl hexanoate (~ 40 %), and (E,E)-farnesyl octanoate (~ 10 %), and this type belongs to the authentic I. picipennis (Bach 1852). Extracts of a second type contain neryl hexanoate (~10 %) and neryl octanoate (~ 90 %), and this type belongs to an Idolus species that apparently has been overlooked to date, presumably due to similarity with the authentic I. picipennis and insufficient material in collections. Synthetic blends of the identified compounds in their naturally-occurring ratios, as well as the main compounds alone, proved to be highly attractive to swarming males of the respective species in the field. A strong species-specific attraction also was observed in a locality where both species co-occur, thus confirming effective reproductive isolation. This study shows the potential of sex pheromones for monitoring rare and threatened insects as well as for detecting hitherto unknown cryptic species.

Crematoenones - a novel substance class exhibited by ants functions as appeasement signal.

BACKGROUND: Parasitic, commensalistic, and mutualistic guests in social insect colonies often circumvent their hosts' nestmate recognition system to be accepted. These tolerance strategies include chemical mimicry and chemical insignificance. While tolerance strategies have been studied intensively in social parasites, little is known about these mechanisms in non-parasitic interactions.Here, we describe a strategy used in a parabiotic association, i.e. two mutualistic ant species that regularly share a common nest although they have overlapping food niches. One of them, Crematogaster modiglianii, produces an array of cuticular compounds which represent a substance class undescribed in nature so far. They occur in high abundances, which suggests an important function in the ant's association with its partner Camponotus rufifemur. RESULTS: We elucidated the structure of one of the main compounds from cuticular extracts using gas chromatography, mass spectrometry, chemical derivatizations and nuclear magnetic resonance spectroscopy (NMR). The compound consists of two fused six-membered rings with two alkyl groups, one of which carries a keto functionality. To our knowledge, this is the first report on the identification of this substance class in nature. We suggest naming the compound crematoenone.In behavioural assays, crematoenones reduced interspecific aggression. Camponotus showed less aggression to allospecific cuticular hydrocarbons when combined with crematoenones. Thus, they function as appeasement substances. However, although the crematoenone composition was highly colony-specific, interspecific recognition was mediated by cuticular hydrocarbons, and not by crematoenones. CONCLUSIONS: Crematenones enable Crematogaster to evade Camponotus aggression, and thus reduce potential costs from competition with Camponotus. Hence, they seem to be a key factor in the parabiosis, and help Crematogaster to gain a net benefit from the association and thus maintain a mutualistic association over evolutionary time.To our knowledge, putative appeasement substances have been reported only once so far, and never between non-parasitic species. Since most organisms associated with social insects need to overcome their nestmate recognition system, we hypothesize that appeasement substances might play an important role in the evolution and maintenance of other mutualistic associations as well, by allowing organisms to reduce costs from antagonistic behaviour of other species.

First sex pheromone of the order strepsiptera: (3R,5R,9R)-3,5,9-trimethyldodecanal in Stylops melittae KIRBY, 1802.

The twisted-wing parasites (Strepsiptera) are an unusual and small order of insects with about 600 known species. As obligate endoparasitoids, they develop and spend most of their lives living in other insects. Adults show an extreme sexual dimorphism: The free-living males have large eyes, branched antennae, reduced forewings, and well developed hind wings, while the neotenic females of most species lack all external characters that normally define an insect, remain endoparasitic, and only extrude the cephalothorax from the host. Due to the males' short life span of only a few hours, there must be an efficient means of mate finding. This is believed to be mediated by chemical cues released by virgin females. Here, we report the first identification and synthesis of a female-produced strepsipteran sex pheromone, (3R,5R,9R)-3,5,9-trimethyldodecanal, from Stylops melittae, a species parasitizing andrenid bees. We found this highly EAD-active compound to be present in cephalothoraxes of and released from unmated females, and synthetic samples proved to be extremely attractive when offered in the field during the swarming period of the males. The structural features of this new natural compound may further support the re-establishment of the Strepsiptera as the closest living relatives of the Coleoptera.

Sex Pheromone of Agriotes acuminatus (Stephens, 1830) (Coleoptera: Elateridae).

The click beetle species Agriotes acuminatus is distributed in open deciduous forests throughout a large area in Europe. In order to identify its sex pheromone, gland extracts of female beetles were investigated by using GC/MS. Neryl butanoate and 2,6-dimethyl-(Z,E)-2,6-octadien-1,8-diol dihexanoate, in a ratio of approximately 1:5, were the only volatile compounds present in the extracts. Structures of both esters were confirmed by synthesis. Field experiments revealed a strong attraction of A. acuminatus males towards neryl butanoate, which could be synergistically enhanced by addition of 2,6-dimethyl-(Z,E)-2,6-octadien-1,8-diol dihexanoate. The latter compound alone did not show any attractive effect. While all Agriotes spp. investigated to date use geranyl and/or (E,E)-farnesyl esters as sex pheromones, the nerol derivatives of A. acuminatus are the first (Z)-2-configurated pheromones within this genus.

Mate finding in the parasitic wasp Cephalonomia tarsalis (Ashmead): more than one way to a female's heart.

The parasitic wasp, Cephalonomia tarsalis (Hymenoptera: Bethylidae), parasitizes larvae of the sawtoothed grain beetle, Oryzaephilus surinamensis (L.) (Coleoptera: Silvanidae), and is used for biological control of this worldwide pest of stored grain. To study the hypothesis that C. tarsalis not only mates at its natal patch but also uses olfactory cues to find mating partners elsewhere, we investigated semiochemical use by male C. tarsalis. Olfactometer experiments revealed that male C. tarsalis are arrested by odors emanating from the cocoons of conspecifics, from young unmated females, and from feces of the host. Dodecanal, which was identified from extracts of filter paper contaminated by young females, had an arresting effect on males but not on females and was, therefore, considered as a sex pheromone. These findings indicate that C. tarsalis is a species with partial local mate competition. Males mate with females: 1) at the emergence site following location of females by sex pheromones from their cocoons, and 2) after dispersal from the natal patch following location of females directly by dodecanal and indirectly by unidentified sexual kairomones from host feces.

Sex pheromone of Elater ferrugineus L. (Coleoptera: Elateridae).

The rare European click beetle, Elater ferrugineus L., develops exclusively in old, hollow deciduous trees. As a result of massive habitat loss caused by modern forestry, it is threatened throughout its entire distribution range and regarded as an indicator species for undamaged natural forests. As E. ferrugineus lives cryptically and its populations are frequently overlooked, we investigated its sex pheromone to develop a reliable detection tool. Pheromone gland extracts of single female E. ferrugineus were examined by using gas chromatography-mass spectrometry (GC-MS). All samples contained 7-methyloctyl 5-methylhexanoate, 7-methyloctyl octanoate, 7-methyloctyl 7-methyloctanoate, and 7-methyloctyl (Z)-4-decenoate in a ratio of approximately 1:1:3:3. Structures of all four esters, which have not been reported as pheromone compounds before, were confirmed by synthesis. A blend of the components was tested in the field and proved to be attractive for E. ferrugineus males, which were found to swarm exclusively during the day. This blend provides a noninvasive and effective monitoring method for this cryptic species, promising future collection records of E. ferrugineus in regions where it exists below the limit of detection by conventional collecting methods.

A male sex pheromone in a parasitic wasp and control of the behavioral response by the female's mating status.

Male insects may increase their chance of successful reproduction by releasing pheromones that attract females or elicit sexual acceptance. In parasitic wasps, male pheromones have been suggested for a few species but no chemicals have been identified so far. Here we report the first identification of a male sex pheromone in parasitic Hymenoptera. In abdomens of male jewel wasps, Nasonia vitripennis Walker, we found a mixture of (4R,5R)- and (4R,5S)-5-hydroxy-4-decanolide (HDL), which was released intermittently and attracted virgin females, but no males, in an olfactometer bioassay. However, only a few minutes after copulation mated females avoided the male-derived pheromone. Neither preference nor avoidance was shown by mated females after 24 h and even after they had been allowed to oviposit for 6 days. Nasonia vitripennis females normally mate only once. Thus, their variable response to the sex attractant depending on the mating status makes sense from an evolutionary perspective. Firstly, it increases the chance of virgins to be inseminated. Secondly, by terminating the response or even avoiding the male pheromone, mated females decrease the probability of encountering males and being disturbed by their courtship activities when searching for new oviposition sites.

Foreign-language skills in rove-beetles? Evidence for chemical mimicry of ant alarm pheromones in myrmecophilous Pella beetles (Coleoptera: Staphylinidae).

By using chemical analyses, as well as laboratory and field behavioral tests, we tested the hypothesis that rove beetles of the myrmecophilous genus Pella use alarm pheromone compounds to avert attacks by their host ant Lasius fuliginosus. The secretions of Pellafunestus and P. humeralis contain quinones and different aliphatic compounds, mainly undecane and 6-methyl-5-hepten-2-one (sulcatone). The latter two chemicals are also found in L. fuliginosus pheromone glands. Behavioral tests confirmed that undecane serves as an "aggressive alarm"-inducing pheromone in L. fuliginosus, whereas sulcatone most likely is a "panic-alarm"-inducing pheromone. The main tergal-secretion compounds, various quinones and undecane, individually and in mixtures induced aggression in L. fuliginosus workers. When sulcatone was added to these compounds, the space around the odor source was avoided and a reduced number of aggressive acts observed, suggesting that sulcatone blocks the aggression-inducing effect of undecane and the quinones. These results support the hypothesis that Pella beetles mimic alarm pheromones of their hosts. This is a rare example of chemical mimicry in myrmecophilous insects in which chemicals other than cuticular hydrocarbons are used.

(R)-acetoin-female sex pheromone of the summer chafer Amphimallon solstitiale (L.).

Extracts of Amphimallon solstitiale (L.), a well known, widely distributed and rather common European scarab beetle, were analyzed by GC-MS and GC-EAD. Acetoin - (R):(S) > 9:1 - as well as 2,3-butanediol - (2R,3R): (2S,3S):meso = 1:1:9 - were present in extracts of both males and females. Although (2S,3S)-butanediol did not show any EAD activity, the other compounds elicited strong responses exclusively with male antennae. In contrast, several EAD active green leaf volatiles were detected equally well by male and female antennae. During preliminary field bioassays, (R)-acetoin was highly attractive to swarming males, whereas neither rac-acetoin nor the 2,3-butanediols showed activity. Therefore, (R)-acetoin is the female sex pheromone of A. solstitiale.

Characteristic odor of Osmoderma eremita identified as a male-released pheromone.

Osmoderma eremita (Scopoli) is an endangered scarab beetle living in hollow trees. It has mainly been known for its characteristic odor, typically described as a fruity, peachlike or plumlike aroma. The odor emanating from a single beetle can sometimes be perceived from a distance of several meters. In this paper, we show that the characteristic odor from O. eremita is caused by the compound (R)-(+)-gamma-decalactone, released in large quantities mainly or exclusively by male beetles. Antennae from male and female beetles responded in a similar way to (R)-(+)-gamma-decalactone in electroantennographic recordings. Field trapping experiments showed that (R)-(+)-gamma-decalactone is a pheromone attracting female beetles. Lactones similar to (R)-(+)-gamma-decalactone are frequently used as female-released sex pheromones by phytophagous scarabs. This is, however, the first evidence of a lactone used as a male-produced pheromone in scarab beetles. We propose that the strong signal from males is a sexually selected trait used to compete for females and matings. The signal could work within trees but also act as a guide to tree hollows, which are an essential resource for O. eremita. Males may, thus, attract females dispersing from their natal tree by advertising a suitable habitat. This signal could also be exploited by other males searching for tree hollows or for females, which would explain the catch of several males in our traps.

Identification of pheromones and optimization of bait composition for click beetle pests (Coleoptera: Elateridae) in Central and Western Europe.

Based on analysis of pheromone gland extracts, highly attractive new baits have been developed for three click beetle pests. That for Agriotes brevis is a mixture of geranyl butanoate and (E,E)-farnesyl butanoate, and that for A rufipalpis and A sordidus contains geranyl hexanoate alone. From known data from species populating Russia, optimized bait compositions for species in Central and Western Europe were developed as follows: geranyl octanoate + geranyl butanoate for A lineatus, geranyl isovalerate for A litigiosus, geranyl hexanoate + geranyl octanoate for A obscurus, geranyl butanoate alone for A sputator and (E,E)-farnesyl acetate alone for A ustulatus. Although slight differences were found in gland contents with A litigiosus var laichartingi and fenotypus typicus, nevertheless there were no differences in response to the optimum bait. There were no differences in pheromone composition or response to the optimized bait between the two morphological forms ('black' and 'red') of A ustulatus. As a result of these studies, highly effective pheromone baits are now available for monitoring and population reduction in all important pest click beetle species in Central and Western Europe.

(S)-(+)-linalool, a mate attractant pheromone component in the bee Colletes cunicularius.

Enantiomerically pure (S)-(+)-linalool was the main constituent in the extracts of the cephalic secretions of virgin females, mated females, freshly emerged males, and patrolling males of the solitary bee Colletes cunicularius. After copulation, the content of (S)-(+)-linalool emitted by the female was strongly reduced. Electrophysiological experiments revealed that both enantiomers of linalool elicited responses from the antennae of the males. Field tests using the pure enantiomers and the racemate of linalool showed that the number of male bees attracted was highest for (S)-(+)-linalool. The search flight activity in the mating flight area increased dramatically when patrolling males were presented with (S)-(+)-linalool vs (R)-(-)-linalool. Taken together, these data indicate a mate attractant pheromone function of (S)-(+)-linalool.

Enantiospecific antennal response of bark beetles to spiroacetal (E)-conophthorin.

Optically pure synthetic enantiomers of (E)-conophthorin [(E)-7-methyl-1,6-dioxaspiro[4.5]decane], one of the volatiles affecting coniferophagous bark beetles, were tested on antennae of Ips typographus, I. duplicatus, I. subelongatus, Dendroctonus micans, and five Scolytus spp. by using combined gas chromatography-electroantennographic detection (GC-EAD). EAD dose-responses indicated that all three Ips species perceived only the naturally occurring and quantitatively dominant (5S,7S)-enantiomer, while its antipode, (5R,7R)-(E)-conophthorin was antennally inactive. Response thresholds for the Ips species were estimated as between 0.1 ng and 1 ng, or lower. The antennal responses of the Ips species caused by 100 ng of the (5R,7R)-enantiomer might be due to 1% impurity-(the active (5S,7S)-enantiomer) in the (5R,7R)-sample. At the 50-ng level, D. micans and five angiosperm Scolytus species (S. intracatus, S. mali, S. ratzeburgi, S. rugulosus, and S. scolytus) responded strongly to the (5S,7S)-enantiomer, while the (5R,7R)-enantiomer was antennally inactive. Currently updated knowledge on the natural occurrence, and electrophysiological and behavioral activity of (E)-conophthorin is summarized.

Phenol--another cockchafer attractant shared by Melolontha hippocastani Fabr. and M. melolontha L.

The response of the two most abundant cockchafer species in central Europe, Melolontha hippocastani and M. melolontha, towards phenol, mixtures of phenol with the leaf alcohol (Z)-3-hexen-1-ol and the known cockchafer pheromones, 1,4-benzoquinone (M. hippocastani) and toluquinone (M. melolontha), was investigated in the field. During the swarming period at dusk, phenol attracted males of both species, and enhanced the known attraction of cockchafer males towards (Z)-3-hexen-1-ol. A mixture of phenol plus (Z)-3-hexen-1-ol was less attractive for M. hippocastani males than a mixture of (Z)-3-hexen-1-ol plus 1,4-benzoquinone, whereas phenol plus (Z)-3-hexen-1-ol attracted as many M. melolontha males as a mixture of (Z)-3-hexen-1-ol plus toluquinone. In both species three component mixtures containing phenol, (Z)-3-hexen-1-ol, and the respective benzoquinone did not capture more males than two component mixtures consisting of only (Z)-3-hexen-1-ol and the benzoquinone. A possible role of phenol as another cockchafer sex pheromone component is discussed.

Identification of sex pheromone composition of click beetle Agriotes brevis candeze.

Geranyl butyrate (GB) and (E, E)-farnesyl butyrate (FB) were identified in the pheromone gland extract of females of the click beetle, Agriotes brevis (Candeze) (Coleoptera: Elateridae) as the major sex pheromone components. Polyethylene vial dispensers containing 20-200 mg of a 1:1 mixture caught high numbers of beetles. Captures did not decrease even after 73 days of field exposure of dispensers. At sites where both Agriotes sputator L. and A. brevis were present, the above baits were selectively catching only A. brevis, despite the fact that GB is also the main pheromone component of A. sputator, suggesting that FB has a role in reproductive isolation. In the early part of the season, traps into which the insects could both crawl and fly captured more A. brevis than designs where the insects could only fly in. Trap design was not important later in the season. This indicates the need for future development of a trap suitable for use throughout the whole season.