Elucidation of Dimethylalkylpyrazines from the Ant Streblognathus aethiopicus by GC-FTIR

The presumed mandibular gland secretions from the workers and gamergates of two colonies of Streblognathus aethiopicus have been found to contain a homologous series of 3,5-dimethyl-2-alkylpyrazines (3,5-dimethyl-2-butylpyrazine, 1; 3,5-dimethyl-2-pentylpyrazine, 2; and 3,5-dimethyl-2-hexylpyrazine, 3). The structures of these compounds were determined from their mass spectra along with a comparison of their GC-FTIR spectra with those of all the isomers of a lower homolog. This is the first time that this combination of techniques has been applied to the study of insect pyrazines. The relative amounts and proportions of these compounds were different for gamergates and workers, with the latter containing 2–10 times more total pyrazines and having a higher proportion of 2 and 3. The possible significance of this finding is discussed.     

Constituents of wing gland and abdominal hair pencil secretions of male African sugarcane borer,Eldana saccharina walker (Lepidoptera: Pyralidae)

In addition totrans-3,7-dimethyl-6-octen-4-olide (eldanolide), vanillin, and 4-hydroxybenzaldehyde, identified by French workers in the wing gland and abdominal hair pencil secretions of the male African sugarcane borer,Eldana saccharina, we have, in an earlier note, reported the presence of several other terpenoid, aromatic, and unbranched-chain compounds such as, (Z)-3,7-dimethylocta-2,6-dienoic acid, 6,10,14-trimethyl-2-pentadecanol, 4-hydroxy-3-methoxybenzyl alcohol, 1-octadecane thiol, 16-hexadecanolide, and 18-octadecanolide in these secretions. In the present paper experimental details and spectral evidence supporting the identification of these compounds, as well as the identification of (Z)-9-hexadecenal and cw-3,7-di-methyl-6-octen-4-olide (cis-eldanolide), are reported. Using electroantennography it was found that male and female antennae reacted approximately equally strongly to both secretions. This result was confirmed in analyses of the secretions using coupled gas chromatography-electroantennography and it was found that male as well as female antennae responded to eldanolide. Vanillin, substituted phenols related to vanillin, and some oxygenated monoterpenes elicited weak responses in male and female antennae. In some analyses 6,10,14-trimethyl-2-pentadecanol, present in the secretions of the insect, gave a strong antennal response. The results obtained in dynamic and static headspace determinations showed that several of the organic compounds present in the glandular secretions are released in detectable quantities and are present in widely varying quantitative ratios in the effluvia of individual calling male moths.     

Trail Pheromone of Myrmicine Ant Pristomyrmex pungens

The myrmicine ant Pristomyrmex pungens marks recruitment trails with poison gland secretions. The effective trail pheromone compound is 6-n-pentyl-2-pyrone. Poison gland components were identified by means of gas chromatographic coupled mass spectrometry. The biological activity was examined in trail-following experiments as well as in gas chromatographic coupled electroantennograms. In addition to 6-n-pentyl-2-pyrone, a number of monoterpenes were found in the poison gland secretion, i.e., α-pinene, camphene, β-pinene, myrcene, α-phellandrene, α-terpinene, and limonene. The terpenoid compounds increased the trail-following response only slightly when offered together with 6-n-pentyl-2-pyrone. In contrast to the latter component, synthetic monoterpenes elicited no orientation behavior in trail-following bioassays.     

Linalool in mandibular gland secretion ofColletes bees (Hymenoptera: Apoidea)

Uinalool was identified as the main component of the mandibular gland secretion in females and males of four species ofColletes bees, viz.,C. cunicularius, C. daviesanus, C. impunctatus andC. succinctus. It was also shown to be the dominant volatile compound in the same gland in maleC. floralis (the female of this species has not yet been investigated). Further, in another species,C. similis, linalool is present in the mandibular gland secretions of females and males, but the dominant volatile component in these secretions is geranial, together with neral. Females of the speciesC. fodiens seem to lack monoterpenes altogether; nonadecane is the dominant volatile compound of the cephalic secretion (based on analysis of a single individual). When linalool is put out in the area of nest aggregation ofC. cunicularius, where the males are patrolling, a distinct increase in flight activity is noted. The function of linalool is discussed on the basis of field observations.This report forms part XXI in the series Studies on Natural Odoriferous Compounds.     

Volatile secretions of old world army antAenictus rotundatus and chemotaxonomic implications of army ant dufour gland chemistry

The Dufour glands ofAenictus rotundatus contain a complex mixture of terpenoids with geranylgeraniol comprising over 50% of the secretion. Some novel compounds have been tentatively identified as higher homologs of 1,3,3-trimethyl-2,7-dioxabicyclo[2,2,1]heptane based on GC-MS data. The Dufour gland secretion ofA. rotundatus is more similar in composition to the secretions of members of the subfamily Ecitoninae than to its closer relatives from the tribe Dorylini, a result that further complicates studies on the phylogeny of army ants. The mandibular glands ofA. rotundatus contain a mixture of 4-methyl-3-heptanone and limonene in trace amounts, and the well-developed postpygidial glands contain methyl anthranilate only.     

Mandibular gland allomones ofDasymutilla occidentalis and other mutillid wasps

The mandibular gland secretion of the mutillid wasp,Dasymutilla occidentalis, possesses three short-chained ketones-4-methyl-3-heptanone (4MH), 4,6-dimethyl-3-nonanone (4,6DMN), 4,6-dimethyl-3-octanone (4,6DMO)—and several unidentified compounds. This is the first report of 4,6DMN as a natural product and its synthesis is described. These ketones, which are either known to be ant alarm pheromones or are structurally very similar to ant alarm pheromones, appear to function as allomones against ants, major potential predators of mutillid wasps. The major secretory component, 4-methyl-3-heptanone, which was identified in females and/ or males of the species analyzed within the generaDasymutilla, Timulla, Traumatomutilla, andPappognatha, appears to constitute a chemical character of the defensive secretions of these genera.     

The Mandibular Gland Secretions of the Leaf-Cutting Ants Atta sexdens sexdens and Atta opaciceps Exhibit Intercaste and Intercolony Variations

The mandibular gland secretions of worker castes from wild colonies of the leaf-cutting ants Atta sexdens sexdens and Atta opaciceps were analyzed quantitatively by gas chromatography–mass spectrometry. The secretions comprised a complex mixture of volatile, mainly oxygenated compounds, and their profiles exhibited considerable qualitative and quantitative variations among species and castes. The known alarm pheromone 4-methyl-3-heptanone was common to both species. The elevated relative proportions of this ketone found in the secretions of gardeners and generalists suggest that such castes are primarily responsible for the production and release of the alarm pheromone. Quantitative variations (but no qualitative differences) in the profiles of secretions of soldiers from different colonies of A. sexdens sexdens were detected, supporting the view that intraspecific colony recognition is mediated through mandibular gland secretions. Subsequent laboratory assays showed that, among the compounds identified by GC–MS, 4-methyl-3-heptanone elicited a strong alarm response in workers of A. sexdens sexdens and A. opaciceps.     

Mandibular Gland Secretion in Different Castes of the Leaf-Cutter Ant Atta laevigata

Gas chromatography analyses and behavioral assays showed that Atta laevigata, a highly polymorphic ant species, has a mandibular gland secretion that varies with castes. All castes contain 4-methyl-3-heptanone as the main component and its concentration is proportional to head size. Small workers and soldiers, but not medium size workers, also contain 4-methyl-3-heptanol. Queens show variations in their chemical composition after mating, as virgin males contain a secretion dominated by 4-methyl-3-heptanol, and, in a lesser proportion, 4-methyl-3-heptanone. In mated males these proportions are inverted. The compounds 4-methyl-6-hepten-3-one, 4-methyl-4-hepten-3-one, 6-methyl-tetradecene, and 2,6-dimethyl-2-dodecene are found only in queens. The behavioral response elicited by the secretion is mainly alarm, which is elicited more strongly by glands of larger workers. The results suggest that chemical castes, behavioral castes, and morphological castes overlap in this species.     

Chemical Profiles of Scent Gland Secretions in the Cyphophthalmid Opilionid Harvestmen, <Emphasis Type="Italic">Siro duricorius</Emphasis> and <Emphasis Type="Italic">S. exilis</Emphasis>

Gas chromatographic–mass spectrometric analyses of the scent gland secretions of Siro duricorius and S. exilis (Opiliones, Cyphophthalmi, Sironidae) revealed a set of 24 components, comprising a series of saturated and unsaturated methyl ketones (C11–C15) and four naphthoquinones. Whereas the scent gland secretions of S. duricorius, collected in Austria, and S. exilis from USA were qualitatively nearly indistinguishable (with the exception of acetophenone that was specific to S. duricorius), they distinctly differed in their relative quantitative compositions: major components of the secretion of S. duricorius were 7-tridecen-2-one, tridecan-2-one, undecan-2-one, 1,4-naphthoquinone, 6-methyl-1,4-naphthoquinone (tentatively identified only), and 4-chloro-1,2-naphthoquinone. In contrast, in S. exilis a compound tentatively identified as 6-methyl-4-chloro-1,2-naphthoquinone was present in large amounts (in S. duricorius a trace component), whereas undecan-2-one only occurred in minor quantities. Secretion profiles of juveniles and adults (both sexes) of each species showed high correspondence.This is the first report on the chemistry of scent gland secretions of the opilionid suborder Cyphophthalmi. 4-Chloro-1,2-naphthoquinone was identified as a new exocrine product of arthropods, whereas 1,4-naphthoquinone and the tentatively identified 6-methyl-1,4-naphthoquinone are known constituents of exocrine secretions from one species of palpatorid opilionids, Phalangium opilio. In contrast, all ketones identified were new for opilionid scent glands, although similar ketones are characteristic of scent gland secretions of palpatorid genera Leiobunum and Hadrobunus. With regard to the near-basic position of Cyphophthalmi in currently proposed phylogenetic trees of Opiliones, naphthoquinones and ketones from Siro may represent the condition ancestral to the (derived) naphthoquinone- and ketone-rich secretions in phalangid Palpatores.     

Male-specific volatiles from nearctic and Australasian true bugs (Heteroptera: Coreidae and Alydidae)

Aeration and exocrine gland extracts were analyzed for three Coreidae and two Alydidae. Males of all the species studied emit volatile blends that are probably pheromones, but sexual communication in these insects evolved differently. In the alydids,Riptortus serripes andMirperus scutellaris, the metathoracic scent glands are sexually dimorphic, and the dimorphisms are expressed chemically. Secretions from the male alydids contain high concentrations of esters or alcohols [e.g., (E)-2-hexenyl (Z)-3-hexenoate, (E)-2-hexenyl butyrate, and (E)-2-octenol], while females produce mainly acids and aldehydes [e.g., butyric and hexanoic acids, and (E)-2-hexenal]. In the coreids,Amblypelta lutescens lutescens, Amblypelta nitida, andLeptoglossus phyllopus, the metathoracic scent glands are not sexually dimorphic, but male- and species-specific volatiles are released, apparently from cells in the cuticular epidermis. The coreid male-specific volatiles are primarily monoterpenes and sesquiterpenes, including (–)-(3R)-(E)-nerolidol as the major component fromA. lutescens lutescens (an Australasian species) andL. phyllopus (a Nearctic species). Only (+)-(3S)-(E)-nerolidol is commonly found in plants so (E)-nerolidol from these coreids is environmentally unique because of its chirality.     

Chemical Characters of Two Related Species of Giant Honeybees (Apis dorsata and A. laboriosa): Possible Ecological Significance

The Himalyan honeybee, Apis laboriosa, is sometimes considered to be a form of the rock honeybee, A. dorsata, rather than a separate species. Analyses of potential exocrine compounds produced by both forms revealed that the cephalic and abdominal natural products of these two honeybees shared no common denominators. The sting shaft of workers of A. dorsata is the source of a large series of esters dominated by 1-acetoxy-2-decene. Other major constituents include isopentyl acetate, accompanied by isopentyl propionate, farnesyl acetate, and several other esters. On the other hand, nothing but presumed structural lipids (e.g., ethyl palmitoleate) were identified from sting shafts of workers of A. laboriosa. By contrast, cephalic (including mandibular glands) extracts from workers of A. laboriosa contained -octanoic lactone, whereas comparable extracts of A. dorsata workers contained only structural lipids. The major qualitative differences in the chemical characters between A. laboriosa and A. dorsata are consistent with the designation of these two forms as distinct species.     

Anal gland secretion of the ferret (Mustela putorius formaFuro)

2,2-Dimethylthietane(1),trans-2,3-dimethylthietane(2),cis-2,3-dimethylthietane(3), 2-propylthietane(4), 3,3-dimethyl-1,2-dithiolane(5),trans-3,4-dimethyl-1,2-dithiolane(6),cis-3,4-dimethyl-1,2-dithiolane(7), 2-pentylthietane (8), 3-propyl-1,2-dithiolane(9), quinoline(10), and indole(11) have been identified as components of the anal gland secretion of the ferret,Mustela putorius formafuro. Male and female ferret secretions were indistinguishable except during the breeding season.     

Defensive secretions of new zealand tenebrionids:

The defensive secretions of four species of the genusArtystona endemic to New Zealand differ from those of other tenebrionids in that they contain -pinene and limonene, as well as the more characteristic quinones and alkenes. Adults and larvae ofA. obscura, A. erichsoni, A. rugiceps, andArtystona sp. feed on the lichenParmotrema reticulatum (Taylor), but the terpenes are not sequestered from it. The defensive secretions of the four species show some interspecific variation.     

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.     

Volatile compounds in anal gland of Siberian weasels (Mustela sibirica) and steppe polecats (M. eversmanni)

The volatile constituents in anal gland secretions of two sympatric Mustela species, the Siberian weasel (M. sibirica) and steppe polecat (M. eversmanni), were studied by the headspace technique, followed by gas chromatography–mass spectrometry (GC-MS) analysis. Nine sulfur-containing compounds were identified. They were 2,2-dimethylthietane, (Z)- or (E)-2,4-dimethylthietane, (E)-2,3-dimethylthietane, 2-ethylthietane, (E)-2-ethyl-3-methylthietane, (Z)-2-ethyl-3-methylthietane, 2-propylthietane, 3,3-dimethyl-1,2-dithiacyclopentane, and (Z)-3,4-dimethyl-2,2-dithiacyclopentane. Among them, (E)-2-ethyl-3- methylthietanes, (Z)-2-ethyl-3-methylthietanes, and (Z)-3,4-dimethyl-1,2-dithiacyclopentane were present in the polecat but not in the weasel. The predominant compound was 2,2-dimethylthietane in the weasel and (E)- or (Z)-2,4-dimethylthietane in the polecat. These differences were consistent between the two species, regardless of sex and age and, therefore, could possibly be used for species recognition. In the weasel, 2-ethylthietane was found only in the female, and the relative abundance of several compounds was significantly different between males and females. In the polecat, although no sex-specific volatile compounds were found, males and females differed in the relative abundance of several of the compounds. In both species, the relative abundance of some compounds varied with age. We conclude that these volatile compounds can be used to communicate information about species, sex, and age.     

Virgin Queen Mandibular Gland Signals of Apis mellifera capensis Change with Age and Affect Honeybee Worker Responses

The mandibular gland secretions of Apis mellifera capensis virgin queens were analyzed by gas chromatography–mass spectroscopy. Changes in the patterns of the mandibular gland volatiles of A. m. capensis virgin queens were followed from emergence until 14-d old. Ontogenetic changes in the mandibular gland secretions were largely quantitative in nature, delineating the age categories (global R = 0.612, P = 0.001), except for 7- and 14-d-old queens, which cannot be separated on their mandibular gland profiles (P = 0.2). (E)-9-Oxodec-2-enoic acid (9ODA) contributes most and most consistently to the dissimilarity between groups as well as the similarity within groups. Worker reactions to introduced virgin queens of various ages were recorded. Workers showed a significant increase in hostile reactions as queens aged (r = 0.615, N = 20, P < 0.05). Consequently, worker reactions and relative 9ODA production exhibit a positive queen age-dependent response.     

Chemistry of metapleural gland secretions of three attine ants,Atta sexdens rubropilosa,Atta cephalotes,andAcromyrmex octospinosus (Hymenoptera: Formicidae)

The chemical composition of the secretions of the metapleural glands of workers and soldiers of twoAtta species,Atta sexdens rubropilosa andA. cephalotes, and workers ofAcromyrmex octospinosus, has been studied. As indicated by infrared spectrometry and confirmed by the ninhydrin test, the secretions contain chiefly proteins. Of the volatile acidic portion, which is present as ionized salts, phenylacetic acid is the major component in workers and soldiers ofA. s. rubropilosa andA. cephalotes. BothAtta species also contain 3-hydroxydecanoic acid and its homolog as minor components together with indoleacetic acid. While there are qualitative similarities in the acidic composition in the secretions ofA. s. rubropilosa andA. cephalotes, they differ quantitatively. The secretion ofAcromyrmex octospinosus contains 3-hydroxydecanoic and indoleacetic acids, but lacks phenylacetic acid. The bactericidal and fungicidal actions of the three major substances have been confirmed.     

Variation with caste of the mandibular gland secretion in the leaf-cutting antAtta sexdens rubropilosa

InAtta sexdens rubropilosa, a strongly polyethic and polymorphic species of myrmicine ant, the contents of the mandibular gland vary with caste. Small workers of head width 0.5–1.8 mm, those generally engaged in duties inside the nest, contain chiefly 4-methyl-3-heptanone. Larger workers, those chiefly engaged in foraging, and the soldier caste contain a mixture dominated by neral and geranial, with very little of the ketone of the smaller workers. The soldiers have massive glands containing milligram amounts of neral and geranial. Virgin and mated females contain essentially only 4-methyl-3-heptanone, the amount increasing after mating, while virgin males have 4-methyl-3-heptanone and 4-methyl-3-heptanol in approximately equal proportions. Mated males have less secretion and lose the 4-methyl-3-heptanol.     

Behavioral correlates for minor volatile compounds from stink bugs (Heteroptera: Pentatomidae)

Many terrestrial Heteroptera have small, but functional, dorsal abdominal glands as adults. The chemistry, and associated intra- and inter-specific behavior, for dorsal abdominal gland secretions from 10 species representing four genera of Pentatomidae was investigated. Eighteen volatile compounds were identified in species-specific blends from the dorsal abdominal gland secretions ofEuschistus, Acrosternum, andEurydema adults, including aliphatic, aromatic, and terpenoid constituents. Evidence from bioassays is presented that parasitic Tachinidae (Diptera) and Scelionidae (Hymenoptera) use these secretions as kairomones. A field experiment was performed to test the hypothesis that minor volatiles increase the specificity of the main pheromone component from NearcticEuschistus species, methyl (2E,4Z)-decadienoate. However, significantly fewer individuals ofE. tristigmus were captured in traps baited with the complete blend for this species than in traps baited with methyl (2E,4Z)-decadienoate alone. Thus, at the concentrations tested, these kinds of dorsal abdominal gland secretions may be epideictic, promoting spacing in the natural habitat.     

Chemical Defense in Harvestmen (Arachnida,Opiliones): Do Benzoquinone Secretions Deter Invertebrate and Vertebrate Predators?

Two alkylated 1,4-benzoquinones were identified from the defensive secretion produced by the neotropical harvestman Goniosoma longipes (Gonyleptidae). They were characterized as 2,3-dimethyl-1,4-benzoquinone and 2-ethyl-3-methyl-1,4-benzoquinone. We tested the effectiveness of these benzoquinone secretions against several predator types, including invertebrates and vertebrates. Different predators were exposed to the harvestmen's gland secretion or to distilled water in laboratory bioassays. Our results indicate that secretions containing the 1,4-benzoquinones released by G. longipes can be an effective defense against predation, and that the effectiveness of the secretion is dependent on the predator type. The scent gland secretion repelled seven ant species, two species of large wandering spiders, and one frog species, but was not an effective defense against an opossum. Our study also demonstrates that the scent gland secretion of G. longipes can work as a chemical shield preventing the approach of three large predatory ants for at least 10 min. The chemical shield may protect the harvestman against successive attacks of the same ant worker and also allow the harvestman to flee before massive ant recruitment. Our data support the suggestion that chemical defenses may increase survival with some but not all potential predators. This variation in defense effectiveness may result from many interacting factors, including the attack strategy, size, learning ability, and physiology of the predators, as well as the chemical nature of the defensive compounds, type of emission, and amount of effluent released by the prey.