Morphology and ultrastructure of the allomone and sex-pheromone producing mandibular gland of the parasitoid wasp Leptopilina heterotoma (Hymenoptera: Figitidae)

Abstract

Chemical communication by the parasitoid wasp Leptopilina heterotoma is based largely on (−)-iridomyrmecin. The female wasps use (−)-iridomyrmecin as a defensive allomone, a chemical cue to avoid competition with con- and heterospecific females, and as a major component of their sex pheromone to attract males. Males of L. heterotoma produce (+)-isoiridomyrmecin, which is also used for chemical defense. In this study we show that females and males of L. heterotoma produce the iridomyrmecins in a pair of mandibular glands. Each gland consists of a secretory part composed of class 3 gland cells and their accompanying duct cells, as well as a reservoir bordered by a thin intima. The gland discharges between the mandible base and the clypeus. Males have considerably smaller glands than females, which corresponds to the lower amount of iridomyrmecins produced by males. Chemical analyses of the mandibular gland contents showed that the gland of females contained mainly (−)-iridomyrmecin, as well as low amounts of the other previously described iridoid pheromone compounds, while the glands of males contained only (+)-isoiridomyrmecin. The morphology and sizes of the mandibular glands of males and females of L. heterotoma have evolved to the multi-functional use of iridomyrmecin.