Re-Analysis of Abdominal Gland Volatilome Secretions of the African Weaver Ant, Oecophylla longinoda (Hymenoptera: Formicidae)

The African weaver ant, Oecophylla longinoda, is used as a biological control agent for the management of pests. The ant has several exocrine glands in the abdomen, including Dufour’s, poison, rectal, and sternal glands, which are associated with pheromone secretions for intra-specific communication. Previous studies have analyzed the gland secretions of Dufour’s and poison glands. The chemistry of the rectal and sternal glands is unknown. We re-analyzed the secretions from Dufour’s and poison glands plus the rectal and sternal glands to compare their chemistries and identify additional components. We used the solid-phase microextraction (SPME) technique to collect gland headspace volatiles and solvent extraction for the secretions. Coupled gas chromatography–mass spectrometry (GC-MS) analysis detected a total of 78 components, of which 62 were being reported for the first time. These additional components included 32 hydrocarbons, 12 carboxylic acids, 5 aldehydes, 3 alcohols, 2 ketones, 4 terpenes, 3 sterols, and 1 benzenoid. The chemistry of Dufour’s and poison glands showed a strong overlap and was distinct from that of the rectal and sternal glands. The different gland mixtures may contribute to the different physiological and behavioral functions in this ant species.

Identification and evaluation of (3Z,6Z,8E)-dodeca-3,6,8-trien-1-ol as the trail following pheromone on Microcerotermes exiguus (Isoptera:Termitidae)

Trail-following pheromone is one of the most important semiochemical in termites. This pheromone is responsible for the recruitment of individuals from the colony to perform different tasks. The aim of this work was to isolate and identify the trail-following pheromone of Microcerotermes exiguus (Isoptera: Termitidae), a typical termite from the Neotropic, that is considered pest in some crops. Subterranean nest of M. exiguus were collected with a shovel in Caracas, Venezuela in 2010. Different chemical micro-reactions combined with chromatographic analysis of solvent extracts, as well as solid phase microextraction analyses (SPME) were applied to termite sternal glands; besides, some behavioral biossays were undertaken. A peak in the chromatograms from extracts (retention index: 1483), presented a fragmentation pattern with m/z ions: 41; 55; 67; 79; 91; 105; 119; 135; 142; 180, this result alongside behavioral assays allowed us to conclude that (3Z,6Z,8E)-dodeca-3,6,8-trien-1-ol (DTOH) acts as the main component of the trail following pheromone. The estimated optimum concentration for termite recruitment and orientation was around 1 pg/cm, being statistically comparable to the value on trails marked with whole body extracts at concentration of 1 worker/cm. The period of time that this compound takes to recruit other colony members is 13.67 ± 5.76 s and lasts up to two hours. Both analytical and behavioral results provided better understanding on the chemical communication of M. exiguus. This information could be used for the future development of newer pest control methods.

Evaluation of Pheromone Lure as Mass-Trapping Tools for Western Flower Thrips

Frankliniella occidentalis  (Pergande) (Thysanoptera: Thripidae) adult male has sternal glands whose role is to produce pheromones. It is known that there are two major components in the headspace volatiles of thrips adult male that are not present in the headspace volatiles of adult female. Those components, (R)-lavandulyl acetate and neryl (S)-2-methylbutanoate were synthesized for the first time in Romania by "Raluca Ripan" Institute for Research in Chemistry (Cluj-Napoca). We have tested a blend of those in the greenhouse cucumber ( Cucumis sativum ) crops of University of Agricultural Sciences and Veterinary Medicine. Period study lasted in 4 weeks. Blue sticky traps were coated with insect glue on both surfaces and a rubber septum which contained the blend was attached in the center of a side of a trap. Two traps with pheromone lure and one trap without pheromone lure were hung up to a 20 cm distance from the tip of the plant. Both female and males were trapped. We observed a higher percentage of males on pheromone trap. Our data revealed that the total number of western flower thrips caught on pheromone traps ranged between 1537 and 1941 as compared with the total number of thrips caught on control trap (1333). According to our results we conclude that pheromone traps could be effective tools for F. occidentalis mass trapping and for the use in integrated pest management strategies.

Pheromone gland musculature in Phryganeidae: Structural features, postcopulatory modification and taxonomic significance

Ultrastructure of the cells forming the sternal glands in males and both fertilized and virgin females of Phryganea bipunctata Retzius and Phryganea grandis L. has been studied by optical and transmission electron microscopy. The structures involved in the synthesis and excretion of pheromone mixtures consist of 4 types of cells: secretory, canal, muscle and epidermal. The secretory and canal cells form a compound structure where the secretory cells produce the secretion, while the canal cells form the conducting and receiving cuticular canals, which participate in conducting the secretion to the cavity of a cuticular reservoir. The cuticle of the reservoir is rough and has numerous folds. Muscle fibers are situated between the epidermal cells and the secretory cells in several layers, which are perpendicular to each other. The presence of muscle fibers in pheromone glands is in agreement with the eliciting of the droplets from the gland orifice in this family. The structure of muscle fibers changes in inseminated females: they become more loose and apparently non-functional. The ultrastructure of secretory cells of the pheromone glands evidences also the greater functional activity of these glands in females as compared to the cells of males. The presence of muscle fibers in the examined pheromone glands in Trichoptera suggests these structures to be a putative apomorphy of Phryganeidae.

Age and seasonal changes in the semiochemicals of the sternal gland secretions of male koalas (Phascolarctos cinereus)

Male koalas communicate with conspecifics using scent markings from their sternal scent gland. We examined age and seasonal changes in the profile of organic compounds produced by koala sternal glands. Scent exudates from 12 male koalas were collected over a one-year period and analysed by direct-injection gas chromatography–mass spectrometry (GC–MS) of the methanol extract. Carboxylic acids, aldehydes, ketones, and alcohols were found to dominate the scent mixture. Thirty-seven compounds were identified by comparison of their spectra with those in the Wiley 138K library. The identity, complexity and relative concentrations of these compounds were found to vary both seasonally and by age of the individuals, with the most odorous and complex mixtures occurring during the mating season. We suggest that seasonal and age differences in the complexity of the chemical composition of the koala scent gland exudate provides evidence that olfactory communication probably has important ramifications for male reproductive success in the wild.