Dufour's gland secretion in the cell linings of bees (Hymenoptera: Apoidea)

The volatile chemicals, detectable by coupled capillary gas chromatography-mass spectrometry, in the nest cell linings of four species in the bee generaColletes, Andrena, andLasioglossum are identical with, and limited to, the volatile components present in the Dufour's gland of females, suggesting this source for some of their cell-lining constituents. The extractable material that lines the cells ofTrachusa byssina, in contrast, is derived fromPinus resin, to which it can be chemically traced.Contribution number 1738 from the Department of Entomology, University of Kansas, Lawrence.     

Dufour's gland and its role in secretion of nest cell lining in bees of the genusColletes (Hymenoptera: Colletidae)

The liquid secretion of the Dufour's gland in mated females comprises a mixture of macrocyclic lactones, straight chain mono- and dicarboxylic acids, together with trace amounts of di- and trihydroxy monocarboxylic acids and a series ofn-alkanes. Polymerization of the liquid to form the membranous nest cell lining, which also contains alanine and glutamic acid as major constituents, may be mediated by an enzyme from the thoracic salivary gland and voided via the mouth. The composition and structure of the cell linings are similar to those of Wigglesworth's cuticulin.     

Pheromonal cues direct mate-seeking behavior of maleColletes cunicularius (Hymenoptera: Colletidae)

Males of the vernal ground nesting bee,Colletes cunicularius, actively search their nesting aggregations for emerging virgin females. Males often detect and unearth preemergent virgin males and females which have not yet dug up to the soil surface. Field experiments indicate that the odors from one unmated individual are sufficient to both excite males and direct their excavation of the virgin bee. A volatile component of this species' mandibular gland secretion, linalool, increases flight activity and directs local search behavior in aerially patrolling males. Linalool is detectable by coupled gas chromatography-mass spectrometry in association with the digging activities of either sex.     

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.     

Predator deterrence by mandibular gland secretions of bees (Hymenoptera: Apoidea)

Volatile lipids from the mandibular gland secretions of bees (Hymenoptera: Apoidea) are potent olfactory repellents of foraging ants (Formica, Crematogaster) in biologically relevant contexts and quantities. In contrast, differential success in capture of bee and fly prey by predatory asilid flies (Efferia), reduviid bugs (Apiomerus), and arachnids (Agelenopsis, Argiope) is better explained by prey size than by chemical repellence, aposematism, or possession of a sting. Supernormal doses of some allomones, applied to worker honeybees (Apis mellifera) that were fed toArgiope aurantia spiders, elicted more frequent preenvenomation pauses following ensnarement but did not significantly increase other prey-handling times. These pauses merely delayed the bee's demise. Mandibular gland secretions of solitary bees augment their other secondary defenses in at least two contexts:

1. during intranest encounters when repelling intruding ants, and
2. retaliation delivered to their arthropodan predators which, if the bee is nearly too large for the predator to handle, may allow the bee to escape.

     

Host recognition and the study of a chemical basis for attraction by cuckoo bumble bees (Hymenoptera: Apidae)

Species ofPsithyrus (Hymenoptera; Apidae) are obligate bumble bee social parasites. In this study, females ofP. vestalis andP. ashtoni were presented with pentane extracts prepared from different body parts of queens of their respective host species,Bombus terrestris andB. terricola. Parasites of both species were capable of distinguishing host bees from other bumble bee species using chemical cues contained within extracts. Among extracts of several body parts presented to parasites, the abdomen produced the greatest behavioral response, with Dufour's gland and terminal tergal segments eliciting the greatest response among abdominal regions. Extracts of these two body parts obtained fromB. terrestris queens shared a number of compounds, identified by GC-MS. Among the identified compounds are a number that have been reported to be of importance in bee sociochemistry.     

Odor correspondence betweenMelitta females and males of their nest parasiteNomada flavopicta K. (Hymenoptera: Apoidea)

Analyses have been performed with the help of combined capillary gas chromatography and mass spectrometry on volatile secretions emanating from the Dufour glands of femaleMelitta haemorrhoidalis andM. leporina and heads of maleNomada flavopicta, a nest parasite of theMelitta species. It was found that the cephalic secretions ofN. flavopicta males have definite similarities with the Dufour gland secretions of the two species ofMelitta. They all contain octadecyl butyrate as a major component. Monounsaturated alcohols of different chain lengths are also present in the secretions. Beside these compounds,Melitta has some other esters, notably C₁₂-, C₁₄-, C₁₆-, and C₂₀-butyrates as well as C₁₂- and C₁₆-acetates.     

Chemistry of the Dufour's gland secretions of North American andrenid bees (Hymenoptera: Andrenidae)

The volatile components of the Dufour's gland secretions were examined in 22 Nearctic species of andrenid bees representing 10 subgenera. Farnesyl hexanoate was the dominant component in the secretion of 17 species. In others, various terpenoid esters such as geranyl octanoate, farnesyl octanoate and geranylgeranyl octanoate were the major components. Approximately 30 compounds have been identified in the secretions; many are newly identified in andrenid bees. Three different groups of secretions are discerned with exceptions. A discussion of the possible function of the Dufour's gland secretion in the biology of, and its use in, the systematics of these bees is presented.     

Chemistry of the mandibular gland secretion of the Indian beePithitis smaragdula

The mandibular glands of the stem-nesting Indian beePithitis smaragdula contain a mixture of salicylaldehyde, citronellyl acetate, geranyl acetate, pentadecane, heptadecane, ethyl tetradecanoate, and ethyl hexadecanoate. Salicylaldehyde is reported for the first time from a hymenopterous source. The secretion, emitted when the bee is disturbed, is rubbed with the legs over the bee's body and the disturbing object. The reactivity of some of the components in combination with the bee's behavior make the glandular exudate an effective defensive secretion.     

Change in mandibular and mesosomal gland contents of maleXylocopa micans (Hymenoptera: Anthophoridae) associated with mating system

Males ofXylocopa micans employ two mating systems in south-central Texas. They defend territories around flowering wisteria and redbud in March and April, and they maintain nonresource-based or landmark territories in July and August. Mandibular and mesosomal gland contents (analyzed by GC-MS) are different in bees employing the two mating systems. Mandibular glands contain only straight-chain hydrocarbons in bees defending floral resources, but include ethyl oleate in bees defending landmark territories. Mesosomal glands contain saturated, mono- and diunsaturated straight-chain hydrocarbons and methyl and ethyl esters of long-chain fatty acids. The major ethyl ester, ethyl oleate, comprises only 1.1% of mesosomal gland contents in bees defending floral resources but comprises 39.7% of gland content of bees defending landmark territories. These findings are discussed relative to the proposed sex pheromone function ofXylocopa gland secretions.Approved as TA 24821 by the Director of the Texas Agriculture Experiment Station.     

Exocrine secretions of bees X. 3,7-Dimethyldeca-2,6-dien-1,10-diol: A sex-specific compound fromNomada annulata (Hymenoptera: Anthophoridae)

3,7-Dimethyldeca-2,6-dien-1,10-diol was isolated from male cephalic extracts of the cleptoparasitic or cuckoo bee,Nomada annulata. The compound is absent in female head extracts. This diol, previously known only from a male danaid butterfly, is a new bee natural product and is not found in the volatile exocrine secretions of the host bee,Andrena macra. The role of this compound in this parasite-host system, including the chemical basis ofNomada-Andrena associations, is discussed.     

A comparative study of the exocrine products of cleptoparasitic bees (Holcopasites) and their hosts (Calliopsis) (Hymenoptera: Anthophoridae,Andrenidae)

The cephalic secretion of females of the cleptoparasitic beeHolcopasites calliopsidis contains two main volatiles, 6-methyl-5-hepten-2-one and geranyl acetone. The mandibular gland secretion of its host,Calliopsis andreniformis, on the other hand, contains the two isomeric forms of citral (neral and geranial). Neral and geranial are also produced by mandibular glands of two other species ofCalliopsis and one species in the related genusNomadopsis. The Dufour's gland ofC. andreniformis contains an oily secretion composed of hydrocarbons that are deposited on the brood cell walls and pollen balls providing a waterproof lining for both.     

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.     

Mandelonitrile in larval secretion of mountain ash sawfly,Pristiphora geniculata (Hymenoptera: Tenthredinidae)

The larval defensive secretion of the mountain ash sawfly,Pristiphora geniculata, contains seven volatile components. They include benz-aldehyde, borneol, bornyl acetate, mandelonitrile, and C₁₄, C₁₆, and C₁₈ acetates.     

Nerol: An alarm substance of the stingless bee,Trigona fulviventris (Hymenoptera: Apidae)

Bees of the genusTrigona and subgenusTrigona possess volatile materials in their mandibular glands, used as alarm substances and as marking pheromones. Heads of workers ofTrigona fulviventris were analyzed by gas chromatography-mass spectrometry. The two major volatile components were nerol ( 50%), and octyl caproate ( 20%). Relative to other substances tested at a Costa Rican nest, treatments containing 20 g of nerol attractedT. fulviventris, depressed numbers of bees leaving the nest by about 50%, and elicited wing vibration and biting. The responses were similar to those obtained with the contents of one worker head. Attraction and biting were also seen in response to captures of colony members by assassin bugs (Apiomerus pictipes) outside a nest entrance; one bee responded in about 15% of the captures. This alarm behavior, although weak, is of interest since it was thought thatT. fulviventris was unusual for its subgenus in its lack of nest defense behaviors.     

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.     

Species,individual and kin specific blends in Dufour's gland secretions of halictine bees

The compositions of Dufour's gland secretions of four sympatric halictine bee species were chemically studied by combined gas chromatography-mass spectrometry. The secretion is composed of C₁₆-C₂₄ macrocyclic lactones, isopentenyl esters, and hydrocarbons. Comparative analyses have revealed that the blends of compounds are species specific. Studies of individual glands belonging to bees of the speciesEvylaeus malachurum have demonstrated that each bee exhibits a specific blend in its Dufour's gland. Nestmate bees (considered as sister bees), however, are more similar to each other than nonrelated bees. The relative importance of species specificity, individual specificity, and similarities between kins are discussed.     

Termite predation byMegaponera foetens (FAB.) (Hymenoptera: Formicidae)

Termite predation by the ponerine ant,Megaponera foetens, is coordinated by chemicals from at least two glands. Columns of ants are guided to termite foraging areas by pheromones originating from the poison apparatus. On finding groups of termites, ants release alkyl sulfides (dimethyl disulfide and trisulfide) from their mandibular glands which attract sister workers who dig, into the termite galleries, in response to other unidentified mandibular gland pheromones.     

Chemical constituents of the chest gland secretion of the thick-tailed galago (Galago crassicaudatus)

The naturally exuded chest gland secretions of adult male and female thick-tailed bush babies were collected directly in capillary tubes. The pure secretion was subjected to GC-MS analysis which revealed three major components. These were identified by comparison with the appropriate standard compounds: benzyl cyanide,p-hydroxybenzyl cyanide, and 2-(p-hydroxyphenyl)ethanol. Analysis of a male and a female secretion indicated that some sexual dimorphism in the relative concentrations of these components may exist.     

Formic acid in caustic cephalic secretions of stingless bee,Oxytrigona (Hymenoptera: Apidae)

The cephalic extracts of two species in the stingless bee genusOxytrigona were analyzed. Extracts made in diethyl ether, and then derivatized with diphenyldiazomethane, revealed large quantities of formic acid, potentially a major defensive secretion of this stingless bee group. We additionally identify several hydrocarbons, aldehydes, ketones, and acetates. Novel diketones identified by others were detected in both species.