The Dufour Gland Contents of Three Species of Euro-African Messor Ants and a Comparison with those of North American Pogonomyrmex (Hymenoptera: Formicidae)

-The Dufour gland secretions of Messor minor, Messor capitatus and Messor bouvieri differ from those of other myrmicine ants so far studied in having no sesquiterpenoids present. M. minor resembles the North American harvester ants, Pogonomyrmex, in containing branched chain hydrocarbons. Messor and Pogonomyrmex appear anomalous among myrmicines and more closely resemble some formicines in this respect. M. minor queens contain chiefly pentadecene (57%), a substance absent from workers (major substance, tridecane, 33%), but are otherwise similar. M. capitatus workers contain tridecane (28%) and nonadecane (26%) and no branched hydrocarbons. M. bouvieriworkers contain linear hydrocarbons, with heptadecadiene (50%) as the major substance, but also small quantities of citronellyl decanoate, a new natural product. Introduction Harvester ants (belonging to the subfamily Myrmicinae) occur in the warmer regions of the Northern Hemisphere [1, 2]. The Old and New World species occupy very similar or even identical ecological habitats and display the same behavioural characteristics of harvesting and storing seeds, but they differ considerably in their stinging abilities. The European and North African Messor have a very much reduced and probably non-functional sting, whereas the North American Pogonomyrmex species possess an extremely effective and powerful sting apparatus. The two main exocrine glands that discharge through the formicid sting are the venom gland and the Dufour gland. The former generally produces the toxic and mostly proteinaceous venom, while the Dufour gland contents can perform a variety of pheromonal functions [3], and moreover has a species-specific composition [4]. This character therefore has recently tPresent address: Department of Zoology, El Minia University, Minia, Egypt. §Author to whom all correspondence should be addressed. (Received 1 March 1989) been used as a reliable chemotaxonomic tool. From an earlier and preliminary study of the Dufour gland substances of two Messorspecies, we formed the view that they bore considerable resemblance to at least one species of Pogonomyrmex [5]. When this present work was done, the only published investigations of Dufour gland substances of harvester ants were two studies on Pogonomyrmex species [6, 7]. In the few species examined, there appeared to be a divergence from the normal pattern of substances found in myrmicine ants, in that they include methyl-branched hydrocarbons in addition to straight chains. We therefore wished to examine again, with the more powerful techniques now available (capillary gas chromatography and linked mass spectrometry), some Messor species and to compare them with the results available on Pogonomyrmex and other myrmicine species. We describe here our examination of Messot minor (Andre), Messor capitatus (Latr.) and Messor bouvieri Bondroit. By chance, in collecting M. minor workers, a number of deallated queens were collected also. We have therefore included data on both queens and workers in order to build up a picture of specificity between