Saw-toothed grain beetleOryzaephilus surinamensis (L.) (Coleoptera: Silvanidae) : Antennal and behavioral responses to individual components and blends of aggregation pheromone

Biology of a putative male aggregation-sex pheromone in Sirex noctilio (Hymenoptera: Siricidae)

A putative male-produced pheromone has recently been described for the global pest of pines, Sirex noctilio, but field-activity has not been demonstrated. This study aimed to investigate the pheromone biology of S. noctilio in more detail. Specifically, we i) analysed effluvia and extracts for additional compounds by gas chromatography coupled with electro-antennographic detection (GC-EAD), mass spectrometry (GC-MS) and two dimensional time of flight mass spectrometry (GC X GC TOF MS), ii) conducted dose-response experiments for putative pheromone components, iii) determined the site of synthesis/ storage of the putative pheromone and iv) determined the release rate of the putative pheromone from males and three types of lures. A blend of four compounds was identified, including the previously described (Z)-3-decenol and (Z)-4-decenol, and two new compounds (Z)-3-octenol and (Z)-3-dodecenol. All compounds elicited a response from both male and female antennae, but the strength of the response varied according to sex, compound and dose tested. (Z)-3-Decenol and (Z)-3-octenol at lower and higher doses, respectively, elicited larger responses in males and females than the other two compounds. (Z)-3-Octenol and (Z)-4-decenol generally elicited larger female than male antennal responses. The site of synthesis and/or storage in males was determined to be the hind legs, likely in the leg-tendon gland. The relative release rate of the major compound by male wasps was shown to be 90 ± 12.4 ng/min, which is between 4 and 15 times greater than that observed from typical lures used previously. These observations are consistent with the hypothesis that these compounds may mediate lek formation in S. noctilio males and lek location in females.

Saw-toothed grain beetleOryzaephilus surinamensis (L.) (Coleoptera: Silvanidae) : Collection, identification, and bioassay of attractive volatiles from beetles and oats

Over 200 beetle- and food-produced volatiles were collected from cultures of the saw-toothed grain beetleOryzaephilus surinamensis (L.) on oats. It proved possible to develop the electroantennogram recording technique for these beetles, despite their small size, allowing volatiles causing antennal responses to be identified by coupled GC-EAG and subsequent GCMS techniques. Three beetle-produced macrolide lactones were identified as (Z,Z)-3,6-dodecadien-11-olide, (Z,Z)-3,6-dodecadienolide, and (Z,Z)-5,8-tetradecadien-13-olide in an average ratio of 4.4∶1∶2. These have been reported as components of the aggregation pheromone from a different population of this species, although the ratio of the components produced was different. Three food volatiles with EAG activity were also identified: 1-octen-3-ol, 3-octanone, and nonanal. A mixture of the six identified volatiles produced similar levels of attraction, in a behavioral assay, to the entire mixture of collected volatiles.

Identification of the sex pheromone of the guernsey carpet beetle,Anthrenus sarnicus Mroczkowski (Coleoptera: Dermestidae)

It has been confirmed that adult virgin females ofAnthrenus sarnicus Mroczkowski exhibit a characteristic headstand posture that is associated with the release of a sex pheromone. Volatiles trapped on filter papers suspended above calling females were attractive to adult virgin males when tested in a two-choice target bioassay. Separate aeration extracts of males and females were analyzed by gas chromatography-mass spectrometry and showed that decanol and decyln-butyrate were released by females only. These components were present in approximately equal amounts and accounted for about 90% of the total area of the chromatogram. Decyl butyrate produced an electroantennogram response with a larger response from males than females. Behaviorally, a mixture of 10μg of decanol and 10μg of decyl butyrate attracted 88% of males and 10μg of decyl butyrate alone attracted 82% of males in the bioassay. The role of decyl butyrate as a sex pheromone is convincing, but this is not the case for decanol.

Scent, sex, and the self-calibrating rat

We propose that one mechanism whereby male rats,Rattus norvegicus, might gauge the reproductive condition of a female is by calibrating a stable odor with an odor that fluctuates through her reproductive cycle. We provide behavioral and histological evidence in support of such a self-calibration model. Male rats sniffed frequently at various body zones of females, and the proportion of sniffs deployed to each zone varied with the females' reproductive condition and relatedness. The females' haunches received more sniffs than any other part of their bodies, irrespective of their relatedness or reproductive condition. Furthermore, males tended to sniff the haunch after sniffing the forequarters, as part of a sequence of sniffing along a female from forequarters to hindquarters. Histology of the skin sebaceous glands indicated that the secretory activity of glands in the haunch, but not those in the forequarters, changed during estrus. Therefore, male rats had the opportunity to judge a female's reproductive status by calibrating the odor of her haunch against that of her forequarters. Self-calibration could represent a means of accommodating differences in odor within individuals.

Grain weevil,Sitophilus granarius (L.): Antennal and behavioral responses to male-produced volatiles

Coupled GC-EAG techniques have been applied to the study of volatiles from the grain weevil,Sitophilus granarius. for the first time. The size of EAG response was independent of the sex of the responding insect but was consistently larger to extracts of males than those of females. This difference was reflected in a behavioral preference for the male extracts by mated adults of both sexes tested together and virgin adults of both sexes tested separately. The GC-EAG results provide evidence for two materials that are released specifically by the males. Using circular dichroism. one has been found to be identical stereochemically with the (2S,3R)-sitophilate reported by others as the aggregation pheromone in a different strain. This enhances the prospects for the development of a single pheromone lure that would be generally applicable whatever the origin of the strain. The small amount of sitophilate found in the males suggests that it is not stored in large amounts. The other material, present in such a small amount that it has yet to be fully characterized, elicits a higher antennal activity than sitophilate and may have a significant role to play in enhancing the trap catch of this economically important pest.

Pheromone-mediated aggregation in nonsocial arthropods: an evolutionary ecological perspective

Although the use of aggregation pheromones has been reported for hundreds of nonsocial arthropod species, the evolutionary ecological aspects of this behavior have received little attention. Despite the elaborate literature on mechanisms, robust data on costs and benefits of aggregation pheromones are scant. Existing literature indicates that, in contrast to the diversity of mechanisms, the ecological conditions in which aggregation pheromones are used are more alike. This points to a few general categories for costs and benefits of aggregation pheromones, and these are discussed. We subsequently review interspecific interactions that may be affected by the use of aggregation pheromones. We encounter a strikingly frequent association of aggregation pheromones with fungi and microorganisms and address cross-attraction by competitor species and exploitation by natural enemies. We show that aggregative behavior by individuals through the use of pheromones can profoundly affect ecological interactions and advocate further evolutionary and ecological investigations of pheromone-mediated aggregation.

Semiochemical-mediated flight responses of sap beetle vectors of oak wilt, Ceratocystis fagacearum

The sap beetle, Colopterus truncatus (Coleoptera: Nitidulidae), is one of the primary vectors of the oak wilt pathogen, Ceratocystis fagacearum, in the north-central United States. Field behavioral assays utilizing various release rates and blends of three methyl-branched hydrocarbon aggregation pheromone components showed that flight responses of this beetle were similar in Illinois and Minnesota populations. In both locations, both sexes of the beetle responded synergistically to a combination of the three-component pheromone and fermenting whole-wheat bread dough. Further, Colopterus truncatus preferred a high release rate over a low release rate of the three-component blend. In both locations, the response of C. truncatus to a simplified version of the pheromone consisting of (2E,4E,6E)-3,5-dimethyl-2,4,6-octatriene (1) and (2E,4E,6E,8E)-3,5,7-trimethyl-2,4,6,8-decatetraene (3) was not significantly different from the response to the three-component blend. An experiment in Illinois with all possible combinations of the components demonstrated that the decatetraene (3) was the crucial component in the blend; of all treatments, the maximal response was elicited by 3 + dough. Chipped bark, phloem, and xylem from northern pin oak, Quercus ellipsoidalis, was not attractive to C. truncatus in Minnesota. During a weekly survey over two seasons in Minnesota, C. truncatus flew in response to the three-component pheromone between early April and early July, with the maximum responses coming on May 4, 2000 and April 20, 2001. During both years, more than 98% of the beetles were trapped between April 14 and June 1. During the same survey, Glischrochilus spp. (Nitiduildae) flew during longer periods of the summer, particularly in 2001. The sex ratio of C. truncatus responding during all experiments was female-biased (1.8:1, female-male), which is characteristic of other male-produced coleopteran aggregation pheromones. Other sap beetles that play a minor role in the pathobiology of C. fagacearum also responded in experiments conducted in Minnesota. Carpophilus brachypterus Say was cross-attracted to the two- and three-component blends of the C. truncatus pheromone and dough, whereas two Glischrochilus spp. were attracted to all treatments that contained dough.

Gas-chromatographic analyses of the subcaudal gland secretion of the European badger (Meles meles) part I: chemical differences related to individual parameters

In many species, chemical signals are important in the context of intraspecific communication. European badgers (Meles meles) use the secretion of their subcaudal gland to mark both the environment and conspecifics. In this paper, we investigated the chemical composition of subcaudal gland secretions and how it varies among individuals according to group membership, season, sex, age, body condition, and reproductive status. We analyzed 66 samples by gas chromatography using a mass-spectrometer as detector. We found 110 different components, of which 21 were present in every profile. The chemical composition of the secretions proved to be highly individual-specific, but no single peak was found to be typical for one of the investigated categories (season, sex, etc.). Analyses of the relative area (% area) that every peak contributed to the overall profile area showed that, in general, group members have more similar profiles than do badgers from different groups. Composition varied over seasons and between sexes and was influenced by age, body condition, and reproductive status. We, therefore, conclude that the secretion not only encodes group membership and individuality as previously assumed, but might also convey information about fitness-related parameters.

Rust-red grain beetle,Cryptolestes ferrugineus, and flat grain beetle,Cryptolestes pusillus: Antennal and behavioral responses to synthetic components of their aggregation pheromones

Antennal and behavioral responses of the rust-red grain beetle,Cryptolestes ferrugineus, and the flat grain beetle,C. pusillus, to synthetic samples of the macrocyclic lactones reported to comprise their aggregation pheromones were investigated. Electroantennogram (EAG) recordings were obtained successfully from both species for the first time. Females of both species showed larger EAGs than males. The EAGs ofC. ferrugineus showed a high degree of specificity for conspecific aggregation pheromone components;C. pusillus showed much less specificity. Behavioral tests were conducted using two-choice pitfall bioassays. Separation of the results into the two effects of activity stimulation and direction finding showed that both effects contributed to the overall response, although sometimes to different extents. The strain ofC. pusillus studied responded equally well to both components of its pheromone, whereas it had been reported previously that only one was active, the other acting as a Synergist and eliciting no response when tested alone. With both species, behavioral response was elicited with a single lactone, suggesting that it might not be necessary to use both components for field use. Particularly surprising was thatC. pusillus showed a greater response to the pheromone components ofC. ferrugineus than to its own. Aeration of the two species and thermal desorption of the collected volatiles confirmed production of the expected lactones, and aeration of authentic lactones showed that the response was not due to the C.ferrugineus pheromone components being markedly more volatile. This response, which seems to be an actual preference, is the first to be discovered among the cucujid beetles and encourages optimism that a practical lure for various species may not need to be as complex as originally feared.