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.     

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.     

Trail-following behavior ofReticulitermes hesperus Banks (Isoptera: Rhinotermitidae)

The behavior ofReticulitermes hesperus Banks pseudergates (workers) was assessed on artificial trails containing different concentrations of sternal gland extract. On nongiadient trails, more pseudergates were recruited to trails of greater pheromone concentration, they traveled a greater distance without pausing, and their rate of locomotion increased over that observed on trails of lesser concentration (positive orthokinesis). Of the individuals pausing before completing trails of high concentration, fewer left the trails or reversed direction (negative klinokinesis) than on trails of lower concentration. Termites walking down concentration gradients failed to complete these trails to the low-concentration termini. At a point representing an average decrease of slightly more than 10-fold in the original concentration of pheromone, individuals reversed their direction of travel and returned to the high-concentration terminus. Termites walking up pheromone gradients proceeded to the high-concentration termini without reversing direction.R. hesperus pseudergates are thus able to orient along a gradient of trail pheromone by longitudinal klinotaxis.     

Chemical ecology ofReticulitermes flavipes (Kollar) andR. virginicus (Banks) (Rhinotermitidae)

Reticulitermes flavipes andR. virginicus have been examined for the presence and possible defense functions of soldiers specific secretions. The cephalic extracts for soldiers of both species contained the identical two major sesquiterpenes which were absent from other castes. The sesquiterpenes have been identified as ₁-cadinene (I) and the corresponding aldehyde (II) by high-resolution nuclear magnetic resonance spectrometry using homonuclear proton decoupling and by high-resolution mass spectrometry. When groups of termite soldiers were exposed to foraging parties of the sympatric native fire ant,Solenopsis geminata, the termites utilized only mechanical defenses. No evidence was obtained to indicate that the ants had been sprayed or coated with either an irritant or toxicant, and there was no evidence that an alarm had been promulgated.     

Cuticular hydrocarbons of dampwood termites,Zootermopsis: Intra- and intercolony variation and potential as taxonomic characters

Colonies ofZootermopsis were collected from the central Sierra Nevada and the Monterey Penninsula in California, and from southern Arizona. Cuticular hydrocarbons were identified by gas chromatography-mass spectrometry (GC-MS) and quantified by gas-liquid chromatography (GLC) for each caste of all colonies. Four consistent and distinct cuticular hydrocarbon patterns, or chemical phenotypes, were identified. Unique and abundant monomethyl- and dimethylalkanes, and ann-alkene provided easy separation of the various phenotypes. Significant differences in the proportions of the various components were found among castes within a colony and colonies within phenotypes from California. Differences in the hydrocarbon proportions for castes were not consistent between colonies. The current taxonomy of the genusZootermopsis recognizes three species. Our identification of four consistent, unique cuticular hydrocarbon phenotypes from the three described species should alert systematists and others to a major concern. If there are truly only three extant species, then the hypothesis that cuticular hydrocarbon profiles in this genus are species specific is not acceptable. Conversely, if cuticular hydrocarbon profiles are truly species specific, then there is at least one new, undescribed species ofZootermopsis.Isoptera: Termopsidae.     

Behavior and survival ofReticulitermes hesperus banks (Isoptera: Rhinotermitidae) on selected sawdusts and wood extracts

Survival ofReticulitermes hesperus workers was assessed inPseudotsuga menziesii, Lysiloma seemanii, andTabebuia ochracea sawdusts; and on heartwood solvent extracts ofP. menziesii, L. seemanii, T. ochracea, Pinus ponderosa, Tabebuia guayacan, and aCentrolobium species. Survival inP. menziesii sawdust was 100% at 5 days and 81–87% at 15 days. Survival inL. seemanii andT. ochracea sawdusts was significantly less over both 5 and 15 days than in the starvation control, indicating toxicity. Survival on filter papers treated with solvent extracts ofT. ochracea andP. ponderosa was significantly less than that on control papers, but onlyP. ponderosa differed significantly from the starvation control. In behavioral assays with groups and with individualR. hesperus workers, extracts ofP. menziesii andP. ponderosa were preferred. In the individual behavioral assays, extracts ofT. guayacan andT. ochracea were repellent. Results of toxicity assays were not predictable from preference assays.     

Behavioral evidence for multicomponent trail pheromone in the termite,Reticulitermes flavipes (Kollar) (Isoptera: Rhinotermitidae)

Evidence is presented for a multicomponent trail pheromone in the eastern subterranean termiteReticulitermes flavipes (Kollar). Choice tests were used to compare strength and persistency of trails made by termites in glass tubes. Tubes connected to termite nests for 24 hr were marked by termites with an extremely long-lasting chemical that persisted for at least one year, and a highly volatile substance that decayed in 15 min. Individual termites varied the trail they deposited under different circumstances. When removed from the nest and placed in a clean tube, they deposited a highly volatile substance. They left stronger and more persistent trails when exploring clean tubes attached to the nest. When they discovered a new food source, they left trails that were more attractive and far more persistent than trails made by exploring or displaced termites. A food trail made by 15 workers was still effective after 24 hr, whereas a trail made by 50 displaced workers, walking one after another through a tube, lasted only 5 min.     

Trail-following pheromones of the rhinotermitidae: Approaches to their authentication and specificity

A method for determining the authenticity of subterranean termite trail pheromones is suggested and utilized to verify the presence of trail pheromones inReticulitermes virginicus, R. flavipes, andR. tibialis. In addition, a possible trail pheromone has been demonstrated forCoptotermes formosanus. A choice bioassay method shows that the above trail pheromones are species specific.     

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.     

Cuticular Hydrocarbons and Soldier Defense Secretions of <Emphasis Type="Italic">Reticulitermes</Emphasis> in Southern California: A Critical Analysis of the Taxonomy of the Genus in North America

Cuticular hydrocarbons (CHC) and soldier defense secretions (SDS) were characterized for collections of Reticulitermes from six counties (Los Angeles, Orange, Riverside, San Bernardino, San Diego, and Santa Barbara) in southern California. Collection sites included the type locality for R. hesperus, Lake Arrowhead (formerly known as Little Bear Lake) in the San Bernardino Mountains. In southern California, there are two CHC phenotypes, SC-A and SC-B, which are easily distinguished by the presence or absence of 5-methyl pentacosane, 5-methyl heptacosane, 5,17-dimethyl pentacosane, and 5,17-dimethyl heptacosane. These phenotypes are similar, but not identical, to previously designated phenotypes of Reticulitermes from northern California. The SDS of termites collected from southern California were characterized; (—)-germacrene A was abundant in all but the four samples from Lake Arrowhead. Soldiers of phenotype SC-A produced >79% germacrene A. The four samples from Lake Arrowhead produced no germacrene A, but contained >78% γ-cadinene. The SDS from the Lake Arrowhead samples were more similar to those of CA-A/CA-A′ from northern California than to any of the CHC phenotypes from southern California. Soldiers of CHC phenotype SC-B produced germacrene A, with the proportion varying from 16.2 to 98.7%. The SDS of SC-B were more similar to those of SC-A than to any of the phenotypes from northern California. The CHC phenotype SC-A found in southern California likely represents R. hesperus and SC-B appears to be a new, as yet undescribed species. We discuss the state of current taxonomic research on Reticulitermes.

Interspecific recognition among termites of the genusReticulitermes: Evidence for a role for the cuticular hydrocarbons

Two species of termites,Reticulitermes (lucifugus) grassei andR. (l.) banyulensis, show a high degree of aggressivity toward each other. The epicuticular signature, recognized by contact, can be extracted using organic solvents, and the removal of the signature abolished all types of aggressive behavior. The signature can be transferred to lures, where it triggers interspecies aggression. It was found to be mainly present in the apolar fraction of the cuticular extracts, which contained only hydrocarbons, are determined by GC/MS techniques. Chemical recognition contributes towards isolation of the two species belonging to theR. lucifugus complex.     

Cuticular Hydrocarbons as Chemotaxonomic Characters of Pine Engraver Beetles (Ips spp.) in the grandicollis Subgeneric Group

Cuticular hydrocarbons were extracted, identified, and evaluated as chemotaxonomic characters from all species of adult Ips pine engraver beetles in the grandicollis subgeneric group. The grandicollis group consists of Ips grandicollis (Eichhoff), I. cribricollis (Eichhoff), I. lecontei Swaine, I. montanus (Eichhoff), I. paraconfusus Lanier, I. confusus (LeConte), and I. hoppingi Lanier. In order to provide outgroups for a phylogenetic analysis, cuticular hydrocarbons were also analyzed from Orthotomicus caelatus (Eichhoff), I. latidens (LeConte) (latidens subgeneric group), and I. pini (Say) (pini subgeneric group). Two hundred forty-eight hydrocarbon components were identified by gas chromatography–mass spectrometry. The members of the grandicollis group provided 206 of these compounds. The components represented eight classes: n-alkanes, alkenes, alkadienes, terminally branched methylalkanes, internally branched methylalkanes, dimethylalkanes, trimethylalkanes, and tetramethylalkanes. Different populations of O. caelatus, I. grandicollis, I. lecontei, I. montanus, I. paraconfusus, I. confusus, and I. hoppingi provided no evidence for interpopulational variation in cuticular hydrocarbons. Single populations only were analyzed for I. latidens, I. pini, and I. cribricollis. Sexual dimorphism in cuticular hydrocarbons occurred only in I. lecontei where females produced eight unique components with a pentatriacontane parent chain. Several phylogenetic analyses based on hydrocarbon phenotypes agreed in general with the established morphologically based system of relatedness and with published phylogenies reconstructed from protein and nucleic acid characters. Nearly all hydrocarbon analyses suggested a close relationship between I. grandicollis and I. cribricollis; between I. lecontei and I. montanus; and among the sibling species I. paraconfusus, I. confusus, and I. hoppingi. The presence or absence of specific n-alkanes (n-docosane, n-triacontane); certain dimethylalkanes (terminally branched with octacosane and triacontane parent chains and internally branched with heptacosane, hentriacontane, and docotriacontane parent chains); and 3,7,11-; 3,7,15-trimethylheptacosane permit facile discrimination of I. paraconfusus, I. confusus, and I. hoppingi. These three sibling species are difficult to resolve by external morphology. These data support the species status of I. hoppingi rather than it being considered a host race of the I. confusus complex. They also support the species status of I. cribricollis rather than it being considered part of I. grandicollis. In contrast to other published phylogenies reconstructed from molecular data, phylogenies reconstructed from cuticular hydrocarbons repeatedly place I. lecontei as an integral part of the grandicollis subgeneric group. Thus, cuticular hydrocarbon and pheromone alcohol composition of I. lecontei support its inclusion in the grandicollis subgeneric group.     

Meliaceae and rutaceae limonoids as termite antifeedants evaluated usingReticulitermes speratus kolbe (Isoptera: Rhinotermitidae)

Four limonoids were evaluated by a no-choice bioassay method as termite antifeedants usingReticulitermes speratus Kolbe. Obacunone showed the highest degree of antifeeding potency (PC₉₅=1133 ppm w/w), followed by nomilin (PC₉₅=4475 ppm), azadirachtin (PC₉₅=65,293 ppm), and limonin (with PC⁹⁵ estimates beyond the bioassay limits), which was the least potent. None of the four limonoids exhibited any evidence of acute toxicity towardsR. speratus, although termites fed on obacunone and nomilin at concentrations higher than their PC₉₅ estimates tend to die faster than those in the unfed treatment. Obacunone and nomilin also showed a drastic antifeedant consumption (AC) reduction effect at concentrations higher than 510 and 1360 ppm, respectively. With azadirachtin and limonin, such an effect was not observed. The present data suggest that both obacunone and nomilin have an absolute antifeeding activity towardsR. speratus.     

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.     

Intercaste,intercolony, and temporal variation in cuticular hydrocarbons ofCopotermes formosanus shiraki (Isoptera: Rhinotermitidae)

We characterized the variation in cuticular hydrocarbon mixtures between seven colonies of the Formosan subterranean termite,Coptotermes formosanus Shiraki, from the same population. We report differences between castes, between colonies, and within the population over time to assess seasonality. Colonies ofC. formosanus from Oahu, Hawaii, were sampled for 25 months. Each month, one sample each of 200 workers, 50 soldiers, nymphs, or alates from each colony was subjected to gas chromatography-mass spectrometry (GC-MS) analysis of the cuticular hydrocarbons. We resolved 39 individual peaks and identified 52 individual or isomeric mixtures of hydrocarbons. Onlyn-alkanes and methyl-branched alkanes occur; no olefins were found. Internally branched monomethylalkanes were the most abundant class of hydrocarbons, representing 45% to 50% of the total 9-;11-;13-Methyl-heptacosane accounted for over 30% of the total hydrocarbon for all castes. 2-Methyl- and 3-methylalkanes comprise approximately 30% of the total. Internally branched dimethylalkanes constitute 15% to 20% of the total cuticular hydrocarbon. Only one trimethylalkane, 13,15,17-trimethylnonacosane, was found in small amounts. The hydrocarbon mixtures of all four castes were similar. Quantitative differences in hydrocarbon mixtures among the castes were easily displayed using canonical discriminant analysis. Soldiers and workers are significantly different from one another and from nymphs and alates. Nineteen peaks are statistically significant between workers and soldiers. Nymphs and alates were not statistically different. We detected statistically significant quantitative differences between colonies in 18 peaks for workers and 12 peaks for soldiers. Each of the colonies ofC. formosanus can be separated from the others by the proportions of their hydrocarbon components. We detected statistically significant differences between months of the year for 12 peaks for workers and four peaks for soldiers; two peaks each for workers and soldiers showed distinct, seasonal trends. This seasonal shift in proportions of hydrocarbons correlates with the production of alates.     

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.     

(Z,Z,E)-3,6,8-Dodecatrien-1-ol, A Major Component of Trail-Following Pheromone in Two Sympatric Termite Species Reticulitermes lucifugus grassei and R. santonensis

Trail-following bioassays show that trails of the two subterranean termites, Reticulitermes lucifugus grassei and R. santonensis, which are sympatric in some areas of southwestern France, are not species specific. Even when tested just above threshold level, trails from pentane extracts of whole workers of R. santonensis are always preferred by both species. If the R. santonensis extract is progressively diluted, the preference is lost. In purified extracts of workers of R. lucifugus grassei that elicited a trail-following response, only one compound is active. It was identified by GC-MS as the same major compound of the trail-following pheromone of R. santonensis: (Z,Z,E)-3,6,8-dodecatrien-1-ol (DTE-OH). The threshold concentration of activity of synthetic DTE-OH was determined to be 10^–3 ng/cm of trail; optimal activity was obtained at 10^–2 ng/cm of trail. The increase of trail-following activity of worker extracts of R. lucifugus grassei after hydrolysis by potassium hydroxide suggests that DTE-OH also is bound to other components in sternal gland secretions. DTE-OH was also identified in alates of R. lucifugus grassei, suggesting that the compound functions both as a trail-following and a sex pheromone, as has been shown to be the case in R. santonensis. This demonstrates the high economy developed by termites in their strategies of chemical communication.     

(Z,E,E)-dodecatrien-1-ol: A minor component of trail pheromone of termite,Coptotermes formosanus Shiraki

In the course of the elucidation of the primary structure of an isolated trail pheromone fromC. formosanus, a minor component that had the same molecular weight as the major trail pheromone, (Z,Z,E)-3,6,8-dodecatrien-1-ol [(Z,Z,E)-DTE-OH], was detected in the mass chromatogram ofm/z 180 of capillary GC-MS. The mass spectrum of the minor component showed a prominent pattern of dodecatrien-1-ol. Chemical analysis demonstrated that the complete structure was (Z,E,E)-DTE-OH. Furthermore, capillary GC-MS-HR-SIM analysis indicated that the component existed only in the workers ofCoptotermes formosanus Shiraki and was not present in workers ofReticulitermes speratus (Kolbe). This minor component may be a species-specific factor ofC. formosanus, although this was not suggested by a two-choice bioassay.     

Chemical taxonomic studies of cuticular hydrocarbons in locusts of theSchistocerca americana complex (Acrididae: Cyrtacanthacridinae): Chemical relationships between new world and old world species

Genetics studies gave an insight into the evolutionary systematics of theS. americana complex. Chemical analysis and comparison of the cuticular hydrocarbons of five species of this complex (S. gregaria, cancellata,americana, piceifrons, andpallens) confirmed the species status previously established by hybridization and also revealed new elements. We have shown the existence of two groups of species:S. gregaria andS. cancellata on one hand,S. americana andS. piceifrons on the other.S. pallens does not fit into either of these groups. These analyses thus have shed some light on the possible origins ofS. gregaria vis-à-visS. cancellata for which an explanation is proposed.