Identification of new homoterpene esters from Dufour's gland of the ponerine ant Gnamptogenys striatula

Extracts of Dufour's gland of the ponerine ant, Gnamptogenys striatula, were analyzed by using the combination of gas chromatography and mass spectrometry. Series of esters of the new homoterpenoids (2E,6)-3,4,7-trimethyl-2,6-octadiene-1-ol (4-methylgeraniol) and (2E,6)-3,4,7-trimethyl-2, 6-nonadiene-1-ol (bishomogeraniol) with unbranched medium-chain fatty acids were identified. Transformation of the chiral natural products into 1,4-di(trifluoroacetoxy)-3-methylpentane and comparison of its gas chromatographic retention time on a modified cyclodextrin phase with that of synthetic optically active reference samples proved the stereogenic center to keep (S)-configuration. (2E,4S,6)-3,4,7-Trimethyl-2,6-octadien-1-yl decanoate and the corresponding dodecanoate are the main volatiles in the extracts.     

Exocrine glands ofPolyrhachis simplex: Chemistry and function

The mandibular glands of the Israeli weaver ant,Polyrhachis simplex, contain a mixture of 4-heptanone, 6-methyl-5-hepten-2-one and 6-methyl-5-hepten-2-ol;its Dufour's gland secretion consists mainly ofn-tridecane. The significance of these glandular secretions in the biology of the weaver ant is discussed.     

Isolation of the trail recruitment pheromone ofSolenopsis invicta

TheSolenopsis invicta trail pheromone is synthesized by the Dufour's gland and is released through the sting apparatus. The recruitment subcategory of theS. invicta trail pheromone was shown to be composed of a mixture of the orientation pheromone, (Z,E)--farnesene and an unidentified homosesquiterpene consisting of three rings and one double bond (C-1). C-1 is present in worker Dufour's glands at only 75 pg per worker equivalent. This is the first report that demonstrates that different exocrine products from the same gland control different subcategories of behavior related to mass recruitment.     

Trail-Following Pheromones in Basal Termites, with Special Reference to Mastotermes darwiniensis

In the framework of an evolutionary study, trail pheromones have been studied in the most basal extant termite, Mastotermes darwiniensis (Mastotermitidae), and two other basal termites, the Termopsidae Porotermes adamsoni (Porotermitinae) and Stolotermes victoriensis (Stolotermitinae). Although workers of M. darwiniensis do not walk in single file while exploring a new environment under experimental conditions and are unable to follow artificial trails in ‘open field’ experiments, they do secrete a trail-following pheromone from their sternal glands. This unique behavior might reflect a primitive function of communication of the sternal gland. The major component of the pheromone appears to be the same in the three basal species: the norsesquiterpene alcohol (E)-2,6,10-trimethyl-5,9-undecadien-1-ol. This represents a new chemical category of trail-following pheromones for termites. The quantity of pheromone was estimated as 20 pg/individual in M. darwiniensis, 700 pg/individual in P. adamsoni, and 4 pg/individual in S. victoriensis. The activity threshold was 1 ng/cm in M. darwiniensis and 10 pg/cm in P. adamsoni. In M. darwiniensis, the trail pheromone was secreted by sternal gland 4 and to a lesser degree by sternal gland 3, sternal gland 5 being almost inactive. This study highlighted phylogenetic relationships between the Mastotermitidae and two subfamilies of the Termopsidae, the Porotermitinae and the Stolotermitinae. Furthermore, it indicated a heterogeneity within the Termopsidae, with Porotermitinae and Stolotermitinae on one hand, and Termopsinae on the other. Finally, Mastotermitidae and Termopsidae, with C14 trail pheromones, are clearly separated from the Kalotermitidae, Rhinotermitidae, and Termitidae that secrete C12 or C20 trail pheromones.     

Chemical communication in the dacetine antDaceton armigerum (Hymenoptera: Formicidae)

Contrary to previous assumptions,Daceton armigerum, the largest ant in the myrmicine tribe Dacetini, employs trail communication. We identified two anatomical sources of trail pheromones: Trails drawn with poison gland contents can last for more than seven days. Trails drawn with the newly discovered sternal glands (in the VIth and VIIth abdominal sternites) are effective but relatively short-lived. In addition, our bioassays revealed that the contents of the mandibular glands elicit alarm behavior, and secretions from the pygidial gland release attraction. When tested with artificial poison gland trails from seven other myrmicine species,Daceton did not exhibit trail following behavior. We confirmed, however, previous findings thatAtta respond toDaceton poison gland trails andSolenopsis followDaceton Dufour's gland trails.     

Hexyl Decanoate, the First Trail Pheromone Compound Identified in a Stingless Bee, Trigona recursa

Foragers of many species of stingless bees guide their nestmates to food sources by means of scent trails deposited on solid substrates between the food and the nest. The corresponding trail pheromones are generally believed to be produced in the mandibular glands, although definitive experimental proof has never been provided. We tested the trail following behavior of recruits of Trigona recursa in field experiments with artificial scent trails branching off from natural scent trails of this stingless bee. First-time recruits (newcomers) did not follow these trails when they were laid with pure solvent or mandibular gland extract. However, they did follow trails made with labial gland extract. Chemical analyses of labial gland secretions revealed that hexyl decanoate was the dominant component (72.4 ± 1.9% of all volatiles). Newcomers were significantly attracted to artificial trails made with synthetic hexyl decanoate, demonstrating its key function in eliciting scent-following behavior. According to our experiments with T. recursa, the trail pheromone is produced in the labial glands and not in the mandibular glands. Hexyl decanoate is the first component of a trail pheromone identified and proved to be behaviorally active in stingless bees.     

Aggregation pheromone of driedfruit beetle,Carpophilus hemipterus Wind-tunnel bioassay and identification of two novel tetraene hydrocarbons

A male-produced aggregation pheromone was demonstrated inCarpophilus hemipterus (L.) (Coleoptera: Nitidulidae) using a wind-tunnel bioassay. Both sexes responded to the pheromone, but the beetles flew in the wind tunnel only after they had been starved for at least several hours. The attractiveness of the pheromone was greatly enhanced by volatiles from a food source, and combinations of pheromone and food volatiles typically attracted 3–10 times more beetles than either source by itself. A variety of food-related sources of volatiles were effective. These included apple juice; a mixture of baker's yeast plus banana; the pinto bean diet used for rearing this beetle; the chemicals propyl acetate, ethanol; and a mixture of acetaldehyde, ethyl acetate, and ethanol. The pheromonal activity resided with a series of 10 male-specific, unsaturated hydrocarbons of 13, 14, and 15 carbon atoms. These were partially separated by HPLC. No single compound was absolutely required for pheromonal activity to be observed, and various subsets of these compounds were active. The most abundant component was (2E,4E,6E,8E)-3,5,7-trimethyl-2,4,6,8-decatetraene. One minor component was (2E,4E,6E,8E)-3,5,7-trimethyl-2,4,6,8-undecatetraene. These structures were proven by synthesis. Together, the synthetic compounds were as active in the wind tunnel as the beetle-derived pheromone.     

(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.     

Role of (3<Emphasis Type="Italic">Z</Emphasis>,6<Emphasis Type="Italic">Z</Emphasis>,8<Emphasis Type="Italic">E</Emphasis>)-Dodecatrien-1-ol in Trail Following,Feeding, and Mating Behavior of <Emphasis Type="Italic">Reticulitermes hesperus</Emphasis>

Trail pheromones mediate communication among western subterranean termites, Reticulitermes hesperus Banks. Repetitive passages of ≥28 termites were required to establish a pheromone trail and trails needed to be reinforced because they lasted <48 hr. The minimal threshold concentration for inducing responses from termite workers and secondary reproductives was between 0.01 and 0.1 fg/cm of (3Z,6Z,8E)-dodecatrien-1-ol (henceforth, dodecatrienol). Workers showed optimal trail-following behavior to dodecatrienol at a concentration of 10 fg/cm. Trails with concentrations >10 pg/cm were repellent to workers. Workers did not detect pheromone gradients, responding equally to increasing or decreasing gradients of dodecatrienol, and termite workers were not able to differentiate between different concentrations of dodecatrienol. Termites preferred dodecatrienol trails to 2-phenoxyethanol trails. Antennae played a key role in trail pheromone perception. Dodecatrienol acted as an arrestant for worker termites (10 fg/cm²) and male alates (5 ng/cm²), whereas sternal gland extracts from females attracted male alates. Workers and alates, upon contact with filter paper disks treated with higher doses (10 fg/cm² and 5 ng/cm², respectively) of dodecatrienol, were highly excited (increased antennation and palpation) and repeatedly returned to the treated disks. Dodecatrienol did not act as a phagostimulant when offered on a paper towel disk. Reticulitermes hesperus is highly responsive to dodecatrienol, and it may play an important role in orientation of workers and alates.     

Sex Pheromone and Trail Pheromone of the Sand Termite <Emphasis Type="Italic">Psammotermes hybostoma</Emphasis>

Within the complex network of chemical signals used by termites, trail pheromones and sex pheromones are among the best known. Numerous recent papers map the chemical identity and glandular origin of these pheromones in nearly all major isopteran taxa. In this study, we aimed to describe the sex pheromone and the trail pheromone of a poorly known sand termite, Psammotermes hybostoma. We identified (3Z,6Z,8E)-dodeca-3,6,8-trien-1-ol (dodecatrienol) as the sex pheromone released by tergal and sternal glands of female imagos and, at the same time, as the trail pheromone secreted from the sternal gland of workers. We conclude that chemical communication in Psammotermes does not differ from that of most other Rhinotermitidae, such as Reticulitermes, despite the presence of a diterpene as a major component of the trail pheromone of Prorhinotermes to which Psammotermes is presumed to be phylogenetically close. Our findings underline once again the conservative nature of chemical communication in termites, with dodecatrienol being a frequent component of pheromonal signals in trail following and sex attraction and, at the same time, a tight evolutionary relationship between the trail following of working castes and the sex attraction of imagos.     

Specificity of laboratory trail following by the argentine ant,Iridomyrmex humilis (Mayr), to (Z)-9-hexadecenal,analogs, and gaster extract

In laboratory trail-following bioassays of Argentine ant workers,Iridomyrmex humilis (Mayr), the geometric isomer, (E)-9-hexadecenal, of the trail pheromone component (Z)-9-hexadecenal elicited insignificant trail following as did the potentially more stable formate analogs, (Z)-7-tetradecenyl formate, (E)-7-tetradecenyl formate, and tetradecyl formate. Further, in direct choice tests, workers showed no preference for gaster extract trails (0.002 ant equiv/cm) over trails of (Z)-9-hexadecenal (0.2 ng/cm). Moreover, a 10-fold increase in synthetic trail concentration to 2.0 ng/cm caused (Z)-9-hexadecenal trails to be significantly preferred over gaster extract trails by trail-following ants.     

Isolation and identification of sex pheromone ofSymmetrischema tangolias (Gyen) (Lepidoptera: Gelechiidae)

The sex pheromone of the South American potato tuber mothSymmetrischema tangolias (syn.:Symmetrischema plaesiosema) was identified as a 2:1 mixture of (E,Z)-3,7-tetradecadien-1-ol acetate and (E)-3-tetradecen-1-ol acetate by means of dual-column GC, EAG, GC-EAD, GC-MS, NMR, and wind-tunnel bioassays. (Z)-5-Tetradecen-1-ol acetate and (Z)-7-tetradecen-1-ol acetate were also identified in the pheromone gland extract. MaleS. tangolias were able to detect these acetates (EAG), but their addition to the two-component sex pheromone did not improve attractiveness. Field trials in Cajamarca and Cusco, Peru, showed that traps baited with the synthetic sex pheromone were able to catch large numbers of maleS. tangolias.     

Isolation,identification, and function of the Dufour gland secretion ofXylocopa virginica texana (Hymenoptera: Anthophoridae)

The Dufour's gland secretion ofXylocopa virginica texana possesses short-term repellency for conspecifics when applied to passion flowers. This secretion contains a number of straight-chain hydrocarbons. The two major components are the methyl esters of palmitic and myristic acid. A mixture of the two esters and two of the available hydrocarbons were as effective as the Dufour's gland extract in eliciting a response in females to the passion flower,Passiflora incarnata, to which the extract was applied.Approved as TA13387 by the Director, Texas Agricultural Experiment Station and conducted in cooperation with the USDA. Supported in part by NSF-DEB-76-03963.     

Macrocyclic lactones and isopentenyl esters in the Dufour's gland secretion of halictine bees (Hymenoptera: Halictidae)

The volatile components of the Dufour's gland secretion of female halictid bees have been examined in 18 Nearctic species belonging toAgapostemon, Augochlora, Augochlorella, Augochloropsis, Dialictus, Evylaeus, Halictus, andLasioglossum. Nine saturated and unsaturated macrocyclic lactones ranging from C₁₈ to C₂₆ have been identified. Four of these compounds, the saturated C₂₆ and the unsaturated C₂₀, C₂₂, and C₂₄ lactones, are new natural products reported for halictine bees. A series of eight esters containing branched C₅-alkenols and fatty acids has been identified in several species. The cell linings and pollen ball inAugochlora pura pura contain the same major lactones as the Dufour's gland. A discussion of the significance of the Dufour's gland secretion for apoid systematics and its function in the Halictidae is presented.     

Chemistry of the Cephalic Labial Gland Secretions of Male Bombus morrisoni and B. rufocinctus, Two North American Bumblebee Males with Perching Behavior

The labial gland secretions from males of the North American bumblebees Bombus morrisoni Cresson and B. rufocinctus Cresson were analyzed by gas chromatography/mass spectrometry. In both species, 3,7,11,15-tetramethyl-2,6,10,14-hexadecatetraenyl acetate was found as the major compound of a complex mixture of alkenols, acetates, hydrocarbons, and wax-type esters. In addition to a mixture of saturated and mono-unsaturated straight chain hydrocarbons, the labial gland of both species contained the isoprenoid hydrocarbons (6E, 10E)-3,7,15-trimethyl-3-methylene-hexadeca-1,6,10,14-tetraene [β-springene], three isomers of 3,7,11,15-tetramethyl-hexadeca-1,3,6,10,14-pentaene [α-springene], and two further unidentified cyclic diterpenes. In B. morrisoni, 3,7,11-trimethyl-2,6,10-dodecatrien-1-ol and 3,7,11,15-tetramethyl-6,10,14-hexadecatrien-1-ol were detected as characteristic alcohols, as well as small amounts of 9-hexadecenol and hexadecanol. Furthermore, a large peak of hexadecyl dodecanoate and minor amounts of 9-hexadecenyl, 9-octadecenyl, and eicosenyl 9-tetradecenoate were found as typical esters in this species. In B. rufocinctus, 9-hexadecenol, hexadecanol, and 9-octadecenol were present in considerable amounts, with their acetates and 9-tetradecenoic, tetradecanoic, hexadecanoic, and 11-octadecenoic acids. The chemical composition of cephalic labial glands in male bumblebees with perching behavior is discussed.     

Volatile compounds from the predatory insectPodisus maculiventris (Hemiptera: Pentatomidae)

In the predatory spined soldier bug,Podisus maculiventris, the dorsal abdominal glands are much smaller in adult females than males. Females produce a mixture of (E)-2-hexenal, (E)-2-octenal, (E)-2-hexenoic acid, benzaldehyde, and nonanal in these glands. The female dorsal abdominal gland secretion may be a close-range pheromone since the dorsal abdominal gland secretion from males has been shown to be a long-range aggregation pheromone in this species. The metathoracic scent gland secretions of male and female spined soldier bugs are apparently identical, and similar to that of other pentatomids, except for the presence of the monoterpene alcohol, linalool.Mention of a commercial product does not constitute an endorsement of this product by the USDA.     

(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.     

Biochemical and behavioral evidence foe hybridization between fire ants,Solenopsis invicta andSolenopsis richteri (Hymenoptera: Formicidae)

Behavioral and biochemical evidence is presented for hybridization between the fire ants,Solenopsis richteri andS. invicta. The response of the two species to extracts of their trail pheromones presented as a point source is clearly species-specific; however, hybrid workers responded to parental Dufour's gland extracts and parental workers responded to Dufour's gland extracts of the hybrid. The behavioral evidence for hybridization was confirmed by gas Chromatograph comparison of the Dufour's gland extracts of the three fire ant forms, which showed a pattern for the hybrid that was intermediate to the two parental species.     

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.     

Pheromonal covariation and kinship in social beeLasioglossum zephyrum (Hymenoptera: Halictidae)

Both males and females of the primitively eusocial beeLasioglossum zephyrum can distinguish among female conspecifics with regard to genealogical relationship. Closely related females covary with respect to Dufour's gland pheromone products which are believed to function in individual or kin recognition. This is the first report of a population-wide parallel between similarity of communicative glandular product and genetic similarity.