Cuticular hydrocarbons of eight species of north american cone beetles,Conophthorus hopkins

A study to determine the degree of similarity and/or diversity among eight of the 15 described species ofConophthorus is reported. Cuticular hydrocarbons were evaluated forC. conicolens, C. ponderosae, C. cembroides, C. edulis, C. radiatae, C. coniperda, C. resinosae, andC. banksianae. Seventy-eight individual and isomeric mixtures of hydrocarbons were identified by gas chromatography-mass spectrometry, includingn-alkanes, alkenes, alkadienes, 2- or 4-methylalkanes, 3-methylalkanes, and single-component and isomeric mixtures of internally branched mono-, di-, and trimethylalkanes. Differences in alkenes and mono-, di-, and trimethylalkanes can be used easily to separate the eight species.Conophthorus conicolens andC. ponderosae contain the most complex blends. Hydrocarbon patterns in three geographically separated populations ofC. ponderosae, each from a different host, are qualitatively identical with the exception of a homologous series of 3,7-dimethylalkanes from adults collected fromPinus lambertiana cones. The latter could comprise a sibling species. Hydrocarbon mixtures of two eastern species,C. resinosae andC. banksianae, are qualitatively identical, supporting the suspicion thatC. banksianae may not be a valid species. Closely relatedC. cembroides andC. edulis have similar combinations of hydrocarbons except for a unique and abundant alkene (C₂₇₁) inC. edulis and two dimethyhexacosanes inC. cembriodes.Coleoptera: Scolytidae.     

Genetic Control of the Enantiomeric Composition of Ipsdienol in the Pine Engraver, Ips pini

The genetic nature of pheromone variation within species has rarely been studied, and never for male-produced long-range pheromones. Males from western North American populations of Ips pini produce predominantly (R)-(−)-ipsdienol, whereas those from eastern North American populations produce higher proportions of (S)-(+)-ipsdienol. From a population in the hybrid zone, we divergently selected lines for the opposing pheromonal types and then created F1, F2, and backcross lines. We formed additional F1, F2, and backcross lines, first by using populations with low (+)-ipsdienol enantiomeric ratios near to and distant from the hybrid zone, and then by using populations with high (+)-ipsdienol enantiomeric ratios near to and distant from the hybrid zone. Three types of analysis were employed: (1) line means analysis; (2) Mendelian analysis of assigned high and low (+)-ipsdienol enantiomeric ratio phenotypes when applicable; and (3) Castle–Wright estimation of the number of effective factors. Dominance at one autosomal locus explains much of the variation in ipsdienol blend between the divergently selected lines. Thus, as in all previously studied female long-range pheromone systems, a major genetic element is implicated. The populations with low (+)-ipsdienol enantiomeric ratios near and distant to the hybrid zone differ negligibly for this trait. We confirmed previous studies showing slightly higher ratios of (+)-ipsdienol at the hybrid zone than in a distant eastern population and reveal a genetic basis for this difference.     

Cuticular Hydrocarbons of Termites of the Hawaiian Islands

Seven species of termites (Isoptera) belonging to three families are found in the Hawaiian Islands. The Kalotermitidae include Neotermes connexus Snyder, Cryptotermes brevis (Walker), Cryptotermes cynocephalus Light, Incisitermes immigrans Snyder, and the recently introduced Incisitermes minor (Hagen). Zootermopsis angusticollis (Hagen), a native of the Pacific Coastal region of North America has become established on Maui and is the sole representative of the Termopsidae. The only rhinotermitid known to be established in the Hawaiian Islands is Coptotermes formosanus Shiraki. A closely related species, Coptotermes vastator Light, has been reported from the Hawaiian Islands, but not recently documented. Cuticular hydrocarbon mixtures were characterized for each of the established and introduced species, as well as for C. vastator from Guam. The diversity of the hydrocarbon mixtures was extreme. At least half the hydrocarbons of C. brevis, C. cynocephalus, I. immigrans, and N. connexus are olefins. C. formosanus and C. vastator make no olefins, but methyl-branched alkanes comprise ca. 95% and 85% of their hydrocarbon mixtures, respectively. Blends of abundant hydrocarbons are species-specific and can be used to identify a given taxon without the diagnostic castes, soldiers, or imagoes. Cuticular hydrocarbon mixtures appear to correlate with habitat requirements.     

Cuticular Hydrocarbons of Buffalo Fly, <Emphasis Type="Italic">Haematobia exigua</Emphasis>, and Chemotaxonomic Differentiation from Horn Fly, <Emphasis Type="Italic">H. irritans</Emphasis>

We determined the quantity and chemical composition of cuticular hydrocarbons of different strains, sexes, and ages of buffalo flies, Haematobia exigua. The quantity of cuticular hydrocarbons increased from less than 1 μg/fly for newly emerged flies to over 11 μg/fly in 13-d-old flies. The hydrocarbon chain length varied from C₂₁ to C₂₉, with unbranched alkanes and monounsaturated alkenes the major components. Newly emerged flies contained almost exclusively C₂₇ hydrocarbons. Increasing age was accompanied by the appearance of hydrocarbons with shorter carbon chains and an increase in the proportion of alkenes. 11-Tricosene and 7-tricosene were the most abundant hydrocarbons in mature H. exigua. Cuticular hydrocarbons of H. exigua are distinctly different from those of horn flies, Haematobia irritans. The most noticeable differences were in the C₂₃ alkenes, with the major isomers 11- and 7-tricosene in H. exigua and (Z)-9- and (Z)-5-tricosene in H. irritans, respectively. Cuticular hydrocarbon analysis provides a reliable method to differentiate the two species, which are morphologically difficult to separate. The differences in cuticular hydrocarbons also support their recognition as separate species, H. exigua and H. irritans, rather than as subspecies.     

Cuticular hydrocarbons of the screwworm,Cochliomyia hominivorox (Diptera: Calliphoridae)

A novel series of 2,X-dimethylalkanes were isolated and identified. The nonpolar fraction of the surface lipids secreted by the adult (5-day-old) screwworm,Cochliomyia hominivorax, contains over 130 different hydrocarbons comprising normal alkanes (32% of the total hydrocarbon), branched alkanes (53%), and monoalkenes (11%). Branched alkanes included monomethylalkanes with substitution in all possible positions except for 4-methylalkanes, internally branched dimethylalkanes, and 2,X- and 3,X-dimethylalkanes. At emergence, adults of both sexes of the 009 strain have nearly identical gas Chromatographic profiles, which diverge as the insect ages. Irradiation of pharate pupae does not affect the hydrocarbon produced.Mention of a commercial or proprietary product in this paper does not constitute an endorsement of that product by the USDA.     

Cuticular hydrocarbons of gregarious and solitary locustsLocusta migratoria cinerascens

The cuticular hydrocarbons ofLocusta migratoria cinerascens—larvae and adults, males and females, gregarious and solitaries—have been investigated by combined gas chromatography-mass spectrometry. The hydrocarbons comprise 52–78% of the cuticular lipids and are divided inton-alkanes (28.7–47.3%), 3-, 4-, and 5-methylalkanes (11.3–15.8%), internally branched monomethylalkanes (13.7–19.9%), and internally branched dimethylalkanes (19.8–35.9%) with seven or nine methylenes between the two branch points. While the sexual dimorphism does not seem to be reflected in the cuticular hydrocarbon composition, clear quantitative variations favoring the longest chain alkanes have been observed between gregarious and solitary locusts, thus revealing a new phase character in these insects.     

Cuticular hydrocarbons of the eastern subterranean termite,Reticulitermes flavipes (Kollar) (Isoptera: Rhinotermitidae)

Major cuticular hydrocarbon components in several castes ofReticulitermes flavipes (Kollar) have been identified and quantitated. Types of hydrocarbons present includen-alkanes, 2-methylalkanes, 3-methylalkanes, 5-methylalkanes, an alkene, and an alkadiene, with a range in carbon numbers from C₂₁ to C₂₆, This is the first report on insect cuticular hydrocarbons in which both 2- and 3-methylalkanes are present, as well as the first report of an insect with a conjugated alkadiene.     

Antennal olfactory responsiveness of three sympatricIps species [Ips avulsus (Eichhoff),Ips calligraphus (Germar),Ips grandicollis (Eichhoff)], to intra- and interspecific behavioral chemicals

Electroantennograms (EAGs) from male and femaleIps avulsus, I. calligraphus, andI. grandicollis to their pheromones and selected host odorants or kairomones verified the presence of antennal olfactory receptors in both sexes of each species capable of detecting ipsdienol, ipsenol,cis- andtrans-verbenol,endo-brevicomin -pinene, frontalin, and verbenone. Each species possesses receptors with lower thresholds and in greater abundance for the compounds they produce and to which they are behaviorally most responsive. Detection of bothIps andDendroctonus pheromones by the three cohabiting species provides a sensory basis for olfactory interactions among the species. Differences in both threshold and saturation levels for EAGs for the various behavioral chemicals could denote differences in specific behavioral roles for each compound.Texas Agricultural Experiment Station Paper Number TA-22463. This research was supported in part by McIntire-Stennis Project 1525, USDA-CR grants 85-CRCR-1-1856 and 86-CRCR-2019 and NATO Collaborative Research Grant 86-0710. The findings, opinions, and recommendations expressed herein are those of the authors and not necessarily those of the U.S. Department of Agriculture. All programs and information of the Texas Agricultural Experiment Station are available without regard to race, ethnic origin, religion, sex, or age.Mention of a trademark, proprietary product, or vendor does not constitute a guarantee or warranty of the product by the U.S. Department of Agriculture and does not imply its approval to the exclusion of other products or vendors that may also be suitable.     

Cuticular Surface Hydrocarbons of Desert Locust Nymphs, Schistocerca gregaria, and Their Effect on Phase Behavior

The quantity of cuticular hydrocarbons is higher in solitarious nymphs of the desert locust, Schistocerca gregaria, compared to gregarious nymphs, but the total hydrocarbon fraction of solitarious nymphs does not significantly divert behavioral transition of isolated nymphs to the gregarious phase, while gregarious hydrocarbon extracts do. This suggests that qualitative differences in composition are responsible for the biological effect. The profile of cuticular hydrocarbon components is similar in the two phases, but some peak ratios differ. Crowding of solitarious nymphs leads to rapid changes in the profile of the hydrocarbon fraction, suggesting that specific hydrocarbons are produced and secreted as a consequence. Isolating previously crowded nymphs has an opposite effect. The composition of cuticular hydrocarbons from the migratory locust, Locusta migratoria, which differs considerably from that of S. gregaria, does not induce the gregarious behavioral phase in solitarious nymphs of the latter.     

Hydrocarbons ofNasutitermes acajutlae and comparison of methodologies for sampling cuticular hydrocarbons of caribbean termites for taxonomic and ecological studies

Using data from the arboreal nestingNasutitermes acajutlae (Holmgren), we propose standard collection and extraction methodology for characterization of cuticular hydrocarbons of termites under field conditions in the tropics. Specifically, we evaluated: (1) the effect of the duration and the number of extractions; (2) the effect of drying termites before extraction; (3) the effect of sample size; (4) the effect of solvents (ethanol versus hexane) on cuticular hydrocarbon profiles. Olefins comprise ca. 70% of the cuticular hydrocarbons ofN. acajutlae. Hydrocarbons consist of two distinct groups: early-eluting components, primarilyn-alkanes and methyl-branched alkanes, and late-eluting compounds, which consist almost exclusively of unsaturated components with one to six double bonds. Soldiers have more early-eluting compounds than workers or alates. Nests from the same island had qualitatively similar, but quantitatively dissimilar hydrocarbon mixtures. Brief extractions of 300 live workers in 10 ml of hexane for only 20 sec produced a hydrocarbon mixture equivalent to a 10-min extraction. Long-term extraction of 300 workers in hexane for two years resulted in different mixtures of hydrocarbons. Drying workers tended to enhance extraction of the less abundant unsaturated compounds such as C_41.4 and C_41.5. A single extraction of a minimum of 100 workers (live or dried), with hexane for 20 sec to 10 min is best; these extraction regimes resulted in mixtures of hydrocarbons that are quantitatively very similar. For quantitative comparisons, extracts from dried samples should not be compared to those from live samples. Storage in ethanol caused numerous unidentified, nonhydrocarbon compounds to be extracted either from the cuticle or from internal tissues.     

Semiochemicals from Fungal Associates of Bark Beetles May Mediate Host Location Behavior of Parasitoids

In laboratory olfactometer bioassays, females of two hymenopteran parasitoid species, Roptrocerus xylophagorum (Ratzeburg) (Hymenoptera: Pteromalidae) and Spathius pallidus (Ashmead) (Hymenoptera: Braconidae), were attracted to odors from bark or bolts of loblolly pine, Pinus taeda L., colonized by bluestain fungi (genus Ophiostoma) associated with the parasitoids' bark beetle hosts. Mock-inoculated bolts and bark were less attractive or unattractive in these bioassays. Bark infested with host larvae that lacked their fungal and other normal microbial associates was attractive to R. xylophagorum females, but was less so than bark infested with larvae possessing their normal complement of associated microbes. In contrast, in oviposition bioassays, R. xylophagorum females spent approximately equal time searching, made similar numbers of oviposition attempts, parasitized similar percentages of hosts, and laid similar numbers of eggs in bark fragments infested with either associate-free or associate-bearing host larvae. Furthermore, in field bioassays using bluestain-inoculated or mock-inoculated loblolly pine bolts as sources of attractants, the numbers of parasitoids attracted by the two treatments did not differ significantly and the two treatments were less attractive than bolts naturally infested with bark beetle larvae. Whereas our laboratory olfactometer data suggest that bark beetle fungal associates may enhance attraction of some parasitoids, our bioassays with associate-free hosts indicate that associate-produced are not required for short-range host location and parasitization. In addition, our field trials indicated that long-range attraction of parasitoids to the host-fungi-tree complex is not caused simply by an interaction between bluestain fungi and tree tissues.     

Cuticular hydrocarbons ofReticulitermes virginicus (Banks) and their role as potential species- and caste-recognition cues

The cuticular hydrocarbon components of four castes ofReticulitermes virginicus (Banks) have been identified and quantitated. Components identified includen-alkanes; 2-, 3-, 11-, 13-, and 15-methyl-alkanes; 11,15-dimethylalkanes, (Z)-9-alkenes; (Z,Z)-7,9-dienes; and (E/Z)-6,9-dienes ranging in carbon number from C₂₁ to C₄₀. All caste forms ofR.virginicus contained the same components, but showed caste-specific proportions. Comparison of these hydrocarbons with those of the sympatric termiteR. flavipes (Kollar) suggest that cuticular hydrocarbons might serve as species- and caste-recognition cues. A bioassay was developed to test this species-recognition hypothesis, with the experimental results supporting the hypothesis.Isoptera: Rhinotermitidae.     

Cuticular Hydrocarbons of Polistes dominulus as a Biogeographic Tool: A Study of Populations from the Tuscan Archipelago and Surrounding Areas

In social insects, the types and proportions of epicuticular lipids may exhibit significant diversity as a result of factors such as age, sex, caste, rank, nest, and relatedness. It is known that these variations can be used by social insects to acquire information regarding conspecific individuals. Recent findings have shown that different populations of Polistes dominulus (Christ.) have distinctly different chemical cuticular profiles, and that wasps are able to recognize individuals of their own population. In this study, we showed that cuticular hydrocarbon patterns of Polistes dominulus are consistent with similarities among northern Tyrrhenian islands, as reported in previous biogeographic studies. Indeed, our findings indicate that cuticular hydrocarbon mixtures of P. dominulus from Capraia and Corsica are grouped together by cluster analysis, while those from Elba and Giglio cluster with cuticular profiles of the mainland wasps (Venturina).     

Cuticular hydrocarbons and defensive compounds ofReticulitermes flavipes (Kollar) andR. santonensis (feytaud): Polymorphism and chemotaxonomy

Colonies ofReticulitermes flavipes andR. santonensis were collected from the southeastern United States (Georgia) and the southwest of France (Charente-maritime). Defensive compounds and cuticular hydrocarbons were identified by gas chromatography-mass spectrometry and quantified by gas chromatography using an internal standard for each caste and all colonies. These analyses show that although the cuticular hydrocarbons ofR. santonensis in Europe andR. flavipes in Georgia are identical, their relative proportions are different. However, the defensive compounds synthesized by their soldiers are different. A strong chemical polymorphism between sympatric colonies ofR. flavipes in the SW United States was detected in terms of both the hydrocarbons of the workers and soldiers and in the defensive secretions of the soldiers. The six defensive secretion phenotypes are based on the presence or absence of terpenes whereas the cuticular hydrocarbon phenotypes are based on significant differences in the proportions of the various components. A multivariate analysis (analysis of principal components) clearly permitted discrimination of four phenotypes (three inR. flavipes and one inR. santonensis) without intermediates. The hydrocarbons responsible for these variations were identified, and it was shown that the variations are neither seasonal nor geographic. The phenotypes of the cuticular hydrocarbons (workers and soldiers) and defensive compounds are linked in each colony, forming in three groups inR. flavipes Georgia, one subdivided into four subgroups according to the defensive secretion phenotypes. The role of these polymorphisms is discussed and ethological tests indicate that the chemical polymorphism do not determine aggressive behavior. The taxonomic significance of these results is considered and two hypothesis are formulated: (1) We only detected a strong genetic polymorphism in one unique species, and we believe thatR. santonensis was introduced into Europe in the last century from oneR. flavipes colony. (2) Chemical variability characterizes the sibling species that can be grouped into the same subspeciesR. flavipes. Unknown mechanisms of reproductive isolation separate them.     

Cuticular Hydrocarbons Provide Reliable Cues of Fertility in the Ant Gnamptogenys striatula

In ca. 150 species of queenless ants, a specialized queen caste is rare or absent, and mated workers take over the role of the queen in some or all of the colonies. Previously, it has been shown that reproduction in queenless ants is regulated by a combination of dominance behavior and chemical fertility signaling. It is unknown, however, whether chemical signals alone can sufficiently regulate reproduction. To investigate this possibility, we studied reproductive regulation in the facultatively queenless ant Gnamptogenys striatula, a species where dominance behavior is rare or absent. Active egg layers and infertile workers showed qualitative and quantitative differences in their cuticular hydrocarbon profile. Five long-chain methyl alkanes, 3,13- and 3,15-dimethyl pentriacontane, 3,13- and 3,15-dimethyl heptentriacontane, and 3,11,15-trimethyl heptentriacontane occurred only on the cuticles of virgin and mated egg layers. Pronounced quantitative differences were found in a further 27 alkenes; alkanes; and mono-, di-, and trimethyl alkanes. Workers that had recently stopped laying eggs had profiles similar to infertile workers, and mating status did not affect this chemical pattern. We conclude that the cuticular hydrocarbon profiles of G. striatula workers provide reliable information about their current fertility. In the interest of colony productivity, this allows reproduction to be regulated without the use of aggression.     

Chemometric Classification of Comb and Cuticular Waxes of the Honeybee Apis Mellifera Carnica

Waxes are important as building material and for the chemical communication of the honeybee Apis mellifera carnica. In this study chemometric tools were established for classifying the different waxes inside the hive. By using gas chromatography in combination with mass spectrometry, components of different types of waxes were analyzed. By considering different substance classes of waxes, discriminant function analyses revealed distinct subtypes of comb waxes and of cuticular waxes. It is shown that the aging of comb wax is in part a spontaneous physicochemical process due to differential volatilities of compound classes with different chain length ranges. On the other hand it is directly influenced by the bees by adding lipolytic enzymes to the comb wax. The data suggest that the varying cuticular wax and comb wax compositions could serve as cues for bees to recognize castes, sexes, or comb age.     

Cuticular hydrocarbons of the paper wasp,Polistes fuscatus: A search for recognition pheromones

The cuticular chemicals of 124 individual wasps (foundresses and workers) from 23 colonies ofPolistes fuscatus were analyzed. The compounds identified, all of which were hydrocarbons, were similar to those of other vespid wasps in that the bulk of the hydrocarbons were 23–33 carbons in chain length. However, the hydrocarbon profile ofP. fuscatus differed from those of its congeners in its proportions of straight-chain alkanes, methylalkanes, and alkenes. Three of the 20 identified hydrocarbons, 13- and 15-MeC₃₁, 11,15- and 13,17-diMeC₃₁, and 13-, 15-, and 17-MeC₃₃, had properties postulated for recognition pheromones: colony specificity, efficacy in assigning wasps to the appropriate colony, heritability, lack of differences between foundresses and workers, and distinctive stereochemistry.     

Novel internally branched,internal alkenes as major components of the cuticular hydrocarbons of the primitive australian antNothomyrmecia macrops Clark (Hymenoptera: Formicidae)

Internally mono- and dimethyl branched, internal alkenes, which constitute most of the cuticular hydrocarbon present on workers of the primitive Australian antNothomyrmecia macrops Clark, have been identified by gas chromatography-mass spectrometry. They are the first such alkenes reported from insects. Also present are alkanes with similar carbon skeletons. The hydrocarbon patterns of three separateNothomyrmecia colonies were very similar.     

Resistance of Neonates and Field-Collected Garter Snakes (Thamnophis spp.) to Tetrodotoxin

Prior studies of tetrodotoxin (TTX) resistance in garter snakes (Thamnophis spp.) have used laboratory-reared neonates as subjects, but the use of field-caught individuals would reduce cost and effort. We compared estimates of TTX resistance in field-caught and laboratory-born garter snakes. We found that a mass-adjusted dose of TTX administered to field-caught garter snakes produces an estimate of a population 50% dose that is comparable and unbiased with respect to those previously reported using laboratory-born neonates. Dose-response curves estimated for three field-caught populations closely matched the curves estimated from neonate data. The method was tested using populations with levels of TTX resistance ranging between approximately 5-90 mass-adjusted mouse units for their respective 50% doses. The technique of using field-caught snakes as test subjects provides larger genetically independent data sets that are more easily obtained. Our results indicate that changes in mass during development parallel ontogenetic shifts in TTX resistance.     

Responses of the Mediterranean Pine Shoot Beetle Tomicus destruens (Wollaston) to Pine Shoot and Bark Volatiles

The pine shoot beetle Tomicus destruens has two dispersal phases per generation. In the first, mature adults move toward trunks of dying pines to lay eggs; in the second, callow adults move toward the shoots of healthy pines for maturation feeding. However, there is no information on the chemical stimuli that govern host selection by T. destruens adults. The aims of this study were: (1) to identify the volatiles released by shoots and bark of stone pine that are behaviorally and electrophysiologically active on T. destruens; (2) to verify which blends and concentrations of such volatiles are differently active on males and females, as well as on callow and mature adults, during the two host search phases (breeding and feeding). A four-arm olfactometer was used to test the behavior of walking T. destruens adults toward various sources of volatiles including fresh shoots and bark, their collected volatiles, and two synthetic blends. For each odor, the behavior of both callow and mature males and females was recorded individually. Shoot and bark extracts were analyzed by coupled gas chromatography and mass spectrometry (GC-MS), and tested by gas chromatography coupled with electroantennography (GC-EAD) on T. destruens males and females. Two blends of two (alpha-pinene and beta-myrcene; blend A) and three (alpha-pinene, beta- myrcene, and alpha-terpinolene; blend B) synthetic compounds, chosen among those that induce EAD responses and known to be attractive for other bark beetle species, were tested in the olfactometer at five concentrations. Insect behavior was affected by the degree of sexual maturation but not by sex. Callow insects were attracted by shoots and their extracts, while mature individuals by bark and its extracts. Six extracted compounds were active on T. destruens antennae: limonene, (Z)-3-hexen-1-ol and beta-caryophyllene, alpha-pinene, beta-myrcene, and alpha-terpinolene. alpha-Terpinolene, released only by bark, was active only on mature insects, whereas (Z)-3-hexen-1-ol, released only by shoots, was active only on callows. Males and females showed similar EAD responses. Of the six extracted volatiles, two were attractive for callow adults (blend A) and three for matures (blend B). In both cases, responses were positively correlated with blend concentration, although a repellent effect was noted at the highest concentrations.