Sex Pheromone of the American Warble Fly, <Emphasis Type="Italic">Dermatobia hominis</Emphasis>: The Role of Cuticular Hydrocarbons

Chemical communication between adults of the American warble fly, Dermatobia hominis (Diptera: Oestridae), was investigated by electroantennography and behavioral bioassays. Significant electroantennographic responses were recorded from both sexes to hexane-soluble cuticular lipids from either sex. Olfactometer tests indicated an attraction between males and females, and between females. Copulatory behavior of males with a white knotted string treated with female extract confirmed production of a sexual stimulant by females. Such behavior was not observed in tests with male extract, demonstrating that the pheromone acts also as a sex recognition factor. Cuticular hydrocarbons of sexually mature female and male D. hominis were identified by Gas chromatography–mass spectrometry and consist of a mixture of saturated n-, monomethyl-, and dimethylalkanes in both sexes. Sexual dimorphism was characterized by a higher relative concentration of dimethylalkanes in males and the presence of alkenes only in females.     

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 and Aggression in the Termite Macrotermes Subhyalinus

Cuticular hydrocarbons are among the prime candidates for nestmate recognition in social insects. We analyzed the variation of cuticular hydrocarbons in the termite species M. subhyalinus in West Africa (Comoë National Park) on a small spatial scale (<1 km). We found considerable variation in the composition of cuticular hydrocarbons among colonies, with four distinct chemical phenotypes. Different phenotypes occurred within each of the four habitats. The difference between these phenotypes is primarily due to unsaturated compounds. A clear correlation between the difference of the hydrocarbon composition and the aggression between colonies was found. This correlation also holds in a multivariate analysis of genetic similarity (measured by AFLPs), morphometric distances (measured by Mahalanobis-distances), as well as geographic distances between colonies. In a more detailed analysis of the correlation between the composition of cuticular hydrocarbons and aggression, we found that no single compound is sufficient to explain variation in aggression between pairings of colonies. Thus, termites seem to use a bouquet of compounds. Multiple regression analysis suggested that many of these compounds are unsaturated hydrocarbons and, thus, may play a key role in colony recognition.     

Unsaturated Cuticular Hydrocarbons Synergize Responses to Sex Attractant Pheromone in the Yellow Peach Moth, Conogethes punctiferalis

Four trienyl hydrocarbons, (Z3, Z6, Z9)-tricosatriene (Z3, Z6, Z9-23:HC), (Z3, Z6, Z9)-pentacosatriene (Z3, Z6, Z9-25:HC), (Z3, Z6, Z9)-heptacosatriene (Z3, Z6, Z9-27:HC), and (Z3, Z6, Z9)-nonacosatriene (Z3, Z6, Z9-29:HC) were identified in a non-polar fraction of the body wax of male and female yellow peach moth, Conogethes punctiferalis. The relative amounts and ratios of these hydrocarbons differed between sexes. In females, the ratios in body wax and pheromone gland extracts were similar, with lesser amounts found in gland extracts. Synergistic effects of these hydrocarbons when added to the known aldehyde pheromone components were assessed in wind tunnel tests. A blend of (E)-10-hexadecenal (E10-16: Ald) and (Z)-10-hexadecenal (Z10-16: Ald) elicited upwind flight and orientation of males to the pheromone source, but arriving males did not remain close to source for very long. Among the hydrocarbons identified, only Z3, Z6, Z9-23:HC enhanced the activity of the aldehyde blend by increasing the time spent close to the source and the number of source contacts. Z3, Z6, Z9-23:HC and (Z9)-heptacosene (Z9-27:HC) also increased close-range responses to the aldehyde blend. The activity of the aldehyde blend plus these two hydrocarbons was similar to that of crude pheromone extract. Positive dose-response relationships between the aldehyde blend and two hydrocarbon mixtures were found. The lowest doses that elicited synergism were 10^?1 female equivalents (of body wax extracts) for the two hydrocarbons, and 10^?2 female equivalents for the total unsaturated hydrocarbon mixture.     

Cuticular Hydrocarbons of Glossina, III: Subgenera Glossina and Nemorhina

The cuticular methyL-branched alkanes of tsetse flies of the subgenera Glossina (sensu stricto, formerly morsitans) and Nemorhina (formerly palpalis) were identified and quantified by capillary gas–liquid chromatography (GC) and gas chromatography–mass spectrometry (GC-MS). Males of Glossina (Nemorhina) are differentiated from G. (Glossina) by dominant 27-, 28-, and/or 29-carbon backbone trimethylalkanes with the methyl positions at 3,7,11-, 4,8,12-, and 3,7,11-, respectively. All females contain major quantities of long-chain internally branched di- and/or trimethylalkanes that were previously implicated as mediators of sexual behavior in males. Taxa within these two subgroups that are closely related and/or conspecific, based upon conventional morphological and ecological criteria, exhibit similar GC patterns and similar internally branched di- and trimethylalkane isomers in females. Examination of these potentially stimulatory methylalkanes may provide reasons for the reproductive isolation of closely related species from each other.     

Cuticular Hydrocarbons of Termites of the British Virgin Islands

A survey of the termites (Isoptera) of 17 islands of the British Virgin Island (BVI) complex yielded eight taxa belonging to three families. The Kalotermitidae include Neotermes mona (Banks), Cryptotermes brevis (Walker), Procryptotermes corniceps (Snyder), and an undetermined species of Incisitermes, likely Incisitermes nr snyderi (Light) or I. incisus (Silvestri). The only rhinotermitid collected is an undetermined species of Heterotermes (Froggatt). Parvitermes wolcotti (Snyder), Nasutitermes costalis (Holmgren), and N. acajutlae (Holmgren) comprise the Termitidae. Cuticular hydrocarbon mixtures were characterized for each of the taxa. Blends of abundant hydrocarbons are species-specific and can be used to identify a given taxon without the diagnostic castes, soldiers, or imagoes, although the species of Incisitermes were not separable on the basis of cuticular hydrocarbons.     

Cuticular lipids of insects: I. Hydrocarbons ofLeucophae maderae andBlatta orientalis

The major hydrocarbons found in the surface lipids of the cockroachesLeucophaea maderae andBlatta orientalis have been identified asn-heptacosane, 11-methylheptacosane, 13-methylheptacosane and 3-methylheptacosane. The hydrocarbons from the two genera of cockroaches are qualitatively identical and quantitatively similar.     

Sources of Variation in Cuticular Hydrocarbons in the Ant Formica exsecta

Phenotypic variation arises from interactions between genotype and environment, although how variation is produced and then maintained remains unclear. The discovery of the nest-mate recognition system in Formica exsecta ants has allowed phenotypic variation in chemical profiles to be quantified across a natural population of 83 colonies. We investigated if this variation was correlated or not with intrinsic (genetic relatedness), extrinsic (location, light, temperature), or social (queen number) factors. (Z)-9-Alkenes and n-alkanes showed different patterns of variance: island (location) explained only 0.2 % of the variation in (Z)-9-alkenes, but 21–29 % in n-alkanes, whereas colony of origin explained 96 % and 45–49 % of the variation in (Z)-9-alkenes and n-alkanes, respectively. By contrast, within-colony variance of (Z)-9-alkenes was 4 %, and 23–34 % in n-alkanes, supporting the function of the former as recognition cues. (Z)-9-Alkene and n-alkane profiles were correlated with the genetic distance between colonies. Only n-alkane profiles diverged with increasing spatial distance. Sampling year explained a small (5 %), but significant, amount of the variation in the (Z)-9-alkenes, but there was no consistent directional trend. Polygynous colonies and populous monogynous colonies were dominated by a rich C_23:1 profile. We found no associations between worker size, mound exposure, or humidity, although effect sizes for the latter two factors were considerable. The results support the conjecture that genetic factors are the most likely source of between-colony variation in cuticular hydrocarbons.     

Sex Pheromone of South American Tortricid Moth Argyrotaenia sphaleropa

By means of electroantennographic detection and gas chromatography-mass spectrometry, the sex pheromone of Argyrotaenia sphaleropa was identified as a mixture of (Z)-11-tetradecenal, (Z)-11,13-tetradecadienal, (Z)-11-tetradecenyl acetate, and (Z)-11,13-tetradecadienyl acetate in the ratio of 1:4:10:40. Best trap catches were obtained with mixtures of (Z)-11-tetradecenal and (Z)-11,13-tetradecadienal in the ratio of 1:4 to 1:9.     

Cuticular Hydrocarbons of the Dampwood Termite, Zootermopsis nevadensis: Caste Differences and Role of Lipophorin in Transport of Hydrocarbons and Hydrocarbon Metabolites

The epicuticular and internal hydrocarbons (HC) from different castes of the dampwood termite Zootermopsis nevadensis were analyzed by gas chromatography–mass spectrometry. The epicuticular HC profiles of workers and alates contained large proportions of n-heneicosane (n-C21), 5-methylheneicosane (5-MeC21), and 5,17- and 5,15-dimethylheneicosane (5,17-, 5,15-diMeC21). Sixty-three HC peaks were identified as normal-, monomethyl-, dimethyl-, and trimethylalkanes up to 41 carbons long. The HC content of the internal tissues was significantly greater than on the epicuticle in all castes examined (2.8-fold in female alates, 5.7-fold in male alates, and 13.7-fold in workers). The hemolymph of all castes, including workers, soldiers, nymphs, and female and male alates, contained large amounts of HC and all hemolymph samples had nearly identical HC profiles. However, the hemolymph profile was remarkably different from the cuticular profile. KBr equilibrium gradient ultracentrifugation of worker hemolymph showed that all HC were associated with a high-density lipophorin (density of 1.12 ± 0.005 g/ml) consisting of two subunits, apolipophorin-I (220 kDa) and apolipophorin-II (82 kDa). After topical application of radiolabeled 3,11-dimethylnonacosane, a HC that is closely related to a native HC, all the internalized HC and radiolabeled lipid metabolites that were recovered from the hemolymph were associated with lipophorin. These findings are consistent with the hypothesis that lipophorin transports HC and some HC metabolites through the hemolymph from the sites of synthesis to the integument and from the integument to metabolic and excretory tissues. In many social insects, different castes have different relative proportions of the same HC and lipophorin appears to play an important role in regulation of the externalization and internalization of HC and, therefore, in the attainment of caste-specific chemical profiles.     

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.     

Male Sex Pheromonal Components Derived from Methyl Eugenol in the Hemolymph of the Fruit Fly Bactrocera papayae

Pharmacophagy of methyl eugenol (ME)--a highly potent male attractant, by Bactrocera papayae results in the hydroxylation of ME to sex pheromonal components, 2-ally-4,5-dimethoxyphenol (DMP) and (E)-coniferyl alcohol (CF). These compounds, which are also male attractants, are then sequestered and stored in the rectal gland prior to their release during courtship at dusk. Chemical analyses of the digestive tract (excluding the crop and rectal gland) showed the absence of the sex pheromonal components and their precursor, ME. However, B. papayae males were attracted to and fed on the ME-fed male hemolymph extracts but not on hemolymph extracts of ME-deprived males. After thin layer chromatography in a hexane:ethyl acetate solvent system, flies were attracted to and fed on the original point on the TLC plate where the hemolymph extract had been spotted, suggesting that the pheromone components were bound in polar complexes. Chemical analyses of the ME-fed male hemolymph and crop extracts revealed the presence of the sex pheromonal components. The presence of the ME-derived pheromonal components and the absence of ME in the hemolymph suggest that the hemolymph is involved in the transportation of sex pheromonal components from the crop to the rectal gland.     

Cuticular lipids of insects: II. Hydrocarbons of the cockroachesPeriplaneta australasiae,Periplaneta brunnea andPeriplaneta fuliginosa

The major cuticular hydrocarbons of the cockroachesPeriplaneta australasiae, Periplaneta brunnea andPeriplaneta fuliginosa aren-tricosane,cis-9-tricosene, 3-methyltricosane, 11-methyltricosane and 13-methylpentacosane. There are as yet unexplained quantitative differences between the hydrocarbon compositions of males and females ofP. australasiae andP. fuliginosa, cis-9-tricosene being a major hydrocarbon of the males only. A series of mono-methyl internally branched hydrocarbons ranging in chain length from 23 to 26 carbons with the methyl branch on the 13th carbon from one end was observed. Minor quantities of other hydrocarbons have been identified.     

Genetic Distance and Age Affect the Cuticular Chemical Profiles of the Clonal Ant Cerapachys biroi

Although cuticular hydrocarbons (CHCs) have received much attention from biologists because of their important role in insect communication, few studies have addressed the chemical ecology of clonal species of eusocial insects. In this study we investigated whether and how differences in CHCs relate to the genetics and reproductive dynamics of the parthenogenetic ant Cerapachys biroi. We collected individuals of different ages and subcastes from several colonies belonging to four clonal lineages, and analyzed their cuticular chemical signature. CHCs varied according to colonies and clonal lineages in two independent data sets, and correlations were found between genetic and chemical distances between colonies. This supports the results of previous research showing that C. biroi workers discriminate between nestmates and non-nestmates, especially when they belong to different clonal lineages. In C. biroi, the production of individuals of a morphological subcaste specialized in reproduction is inversely proportional to colony-level fertility. As chemical signatures usually correlate with fertility and reproductive activity in social Hymenoptera, we asked whether CHCs could function as fertility-signaling primer pheromones determining larval subcaste fate in C. biroi. Interestingly, and contrary to findings for several other ant species, fertility and reproductive activity showed no correlation with chemical signatures, suggesting the absence of fertility related CHCs. This implies that other cues are responsible for subcaste differentiation in this species.     

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).     

Identification of Chemicals Emitted by Calling Males of the Sapote Fruit Fly, <Emphasis Type="Italic">Anastrepha serpentina</Emphasis>

Emissions from sexually active Anastrepha serpentina males were collected by solid-phase microextraction. Calling behavior of wild-type males showed no clear peak during the day, except that it was evident less frequently immediately after daybreak and just before dark. Calling by laboratory males was highest between 8 and 11 h after onset of the photophase, and mating by wild flies occurred mostly between 6 and 10 h after onset of the photophase. Two major components of male emissions were identified as 2,5-dimethylpyrazine (DMP) and 3,6-dihydro-2,5-dimethylpyrazine (DHDMP). DHDMP was synthesized, and the identity of the natural product confirmed by comparison of gas chromatographic retention times and mass spectrum. Emissions of DMP and DHMP were greatest during peak calling behavior, with males emitting up to 1.8 and 3.3 μg/h of DMP and DHDMP, respectively. A minor component, which did not vary with time of day, was identified as 2,3,5-trimethylpyrazine. To our knowledge, this is the first report of 3,6-dihydro-2,5-dimethylpyrazine in nature. D. C. Robacker and R. J. Bartelt are now retired.     

多环芳烃在广州市大气中垂直高度浓度分布和昼夜变化

摘利用TSP大流量采样器分别在2010年8月和12月于广州市某铁塔(50 m和100 m)处进行大气采样,并分析大气样品中多环芳烃(polycyclic aromatic hydrocarbons,PAHs)的浓度分布、组成分布、垂直变化、昼夜变化、季节变化。结果显示:在海拔高度100 m(塔高50 m)的采样点处,广州市大气(气相+颗粒相)中PAHs夏季白天(98 ng/m~3)和夜间(99 ng/m~3)浓度均高于冬季的白天(56 ng/m~3)和夜间(84 ng/m~3);但在海拔高度150 m(塔高100 m)的采样点处,大气中(气相+颗粒相)中PAH夏季白天(53 ng/m~3)和夜间浓度(73 ng/m~3)略低或相当于冬季的白天(62 ng/m~3)和夜间浓度(77 ng/m~3)。     

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.