Epicuticular lipids and fertility in primitively social wasps (Hymenoptera Stenogastrinae) S. TURILLAZZI 1,2 , M. F. SLEDGE 1 , L. DAPPORTO 1 , M. LANDI 1 , D. FANELLI 1 , L. FONDELLI 1 , P. ZANETTI 1 and F. R. DANI 2 1 Dipartimento di Biologia Animale e Genetica and 2 Centro Interdipartimentale di Spettrometria di Massa, Universita` di Firenze, Firenze, Italy Abstract. Lipid cuticular profiles of females of four species belonging to three different genera of stenogastrine wasps are examined in connection with repro- ductive potential (relative ovarian development). Cuticular lipids may not only represent the cues for nestmate discrimination (already behaviourally ascertained in three of the same species), but also allow discrimination of fertile and non fertile individuals. Comparisons with more socially evolved insects are reported and discussed. Key words. Chemical communication, epicuticular lipids, fertility, social wasps, Stenogastrinae. Introduction The outer layer of the insect exoskeleton comprises a mix- ture of lipids that covers the entire body. This layer offers an efficient protection against the loss of water and pene- tration of microorganisms, and has been one of the major contributing factors in the evolutionary success of the insects. The main components of the lipid mixture are long-chained hydrocarbons, mainly alkanes, alkenes and methyl-branched alkanes. Epicuticular hydrocarbons have secondarily acquired communicative roles in many insects. In solitary insects, they may function as contact phero- mones enabling recognition of sexual partners or as kairo- mones when they make the recognition of a host by parasitoids possible (Howard, 1993). In social insects (mainly ants, bees, wasps and termites), cuticular lipids are involved in a number of communicative functions, espe- cially in inter- and intracolonial communication. The pro- portions of cuticular lipid components have been shown to be both species and colony-specific, furnishing potential cues to recognize nestmates and discriminate alien individ- uals and social parasites (Howard, 1993; Smith & Breed, 1995; references in Vandermeer etal., 1998). Recent research has highlighted several additional roles possibly played by cuticular compounds within colonies. One of the most important is the signalling of reproductive status by fertile individuals. Queens and egg-laying individuals are predicted to produce signals of their presence and repro- ductive capacity (e.g. ovarian activity) (Keller & Nonacs, 1993), thus allowing workers, in response, to forego repro- duction and reap inclusive fitness benefits by rearing off- spring produced by the queen. In several ants (Peeters etal., 1999; Liebig etal., 2000), bees (Ayasse etal., 1995) and wasps (Sledge etal., 2001), variation in the proportions of one or more cuticular hydrocarbons may convey informa- tion regarding an individual’s reproductive capabilities. In social wasps, nestmate recognition has been well stud- ied in the genus Polistes (Vespidae, Polistinae), where many facets of this phenomenon are understood, and the involvement of cuticular lipids in nestmate recognition is demonstrated (Singer & Espelie, 1992; Dani etal., 1996; Lorenzi etal., 1997). Nestmate recognition based on cuti- cular hydrocarbons has also been demonstrated in some species of the more advanced social subfamily of the Vespi- dae, the Vespinae (e.g. Vespa crabro, Ruther etal., 1998). However, little is known about the most primitively social subfamily of the Vespidae, the Stenogastrinae. The Steno- gastrinae, or hover wasps, represent a taxon of approxi- mately one hundred species in seven genera inhabiting the forests of South-east Asia from South India to New Guinea Correspondence: Stefano Turillazzi, Dipartimento di Biologia Animale e Genetica, Universita` di Firenze, via Romana 17, 50125, Firenze, Italy. Tel.: þ39 055 2288218; fax: þ39 055 222565; e-mail: turillazzi@dbag.unifi.it Physiological Entomology (2004) 29, 464–471 464 # 2004 The Royal Entomological Society