A first description of the structural organization of two exocrine glands associated with the mandibles of queens of the obligatory slave-making ant Polyergus rufescens is reported. The mandibular gland consists of clustered bicellular secretory units connected by means of cuticular ducts to a big reservoir. The reservoir continues in a duct that opens proximally on the mandible cuticle. Intramandibular glands are isolated bicellular secretory units connected to the external pores through a cuticular duct. No reservoir has been observed. In both cases the secretory cells belong to the 3 rd class. Functional aspects of the investigated glands are discussed taking also into account for the parasitic habit of this slave-making species.
In hymenopteran societies, workers are not always sterile, and may produce parthenogenetically either males (arrhenotoky) or females (thelytoky). Thelytoky however is exceptional, and has been recorded in only four ant species. Here we provide evidence for worker thelytoky in an additional species, the harvesting ant Messor capitatus (Latreille) (Hymenoptera Formicidae Myrmicinae). Two orphaned colonies produced a large amount of worker offspring during 10 months in the laboratory. Dissections showed that reproduction was performed by workers and not by mated worker-like individuals (ergatoids). In some parasitoid wasps, parthenogenetic reproduction is caused by the maternally transmitted bacterium Wolbachia. Using a PCR-based assay we showed that Wolbachia can not be involved in parthenogenesis induction in this species. Finally, we point out reasons for the low Wolbachia susceptibility of parthenogenetic ant species.
In the European slave-making ant Polyergus rufescens, the occurrence of chemical strategies during the initial phase of dependent colony foundation or usurpation was investigated. To test this idea, we analysed the effect of the secretion of different glands (Dufour's, poison, pygidial, rectal, and mandibular) on the behaviour of workers of its common host species, Formica cunicularia (subgenus Serviformica). Workers of another species, Formica rufibarbis (Serviformica), were daubed with these extracts, and introduced into colony fragments of F. cunicularia. The results of a set of laboratory aggression test showed that the secretion of the mandibular, pygidial, rectal, and poison glands do not alter the characteristic aggressive reactions generally performed by resident workers against alien ants. By contrast, the Dufour's gland seems to play a crucial role in the appeasement of residents of the target host colony. In fact, its secretion drastically lowers the degree of overt attacks shown by F. cunicularia workers against the intruders. This chemical strategy probably allows an easier invasion and usurpation of host colonies by newly mated females of P. rufescens.
Some aspects of the chemical communication system employed by the harvesting ant Messor capitatus during foraging were investigated in the laboratory. After locating a conspicuous food item the scouts return home dragging their gaster on the ground. Once inside the nest they run among nestmates and perform an excited motor display. Soon after, groups of workers rush out and move towards the food. Bioassays of different gland extracts showed that nestmates are activated and induced to leave the nest by substances from Dufour's gland. This gland was also found to be the source of the orientation-recruitment trails by which foragers reach newly discovered food sources. The bioassays showed that poison gland extracts are also active in inducing trail following. However, this response was accompanied by typical aggressive reactions by tested ants, suggesting that the poison gland is involved in alarm communication and recruitment towards a source of danger rather than in foraging activities. Some features of the Dufour's gland trail (such as its durability and lack of colony-specificity) are discussed with regard to the ecological requirements of this species.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations鈥揷itations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.