Ectal mandibular gland in Polistes dominulus (Christ) (Hymenoptera, vespidae): ultrastructural modifications over the secretory cycle.

An ultrastructural study was carried out on the secretory activity of the ectal mandibular gland in the wasp Polistes dominulus (foundress and worker females as well as males). Secretory activity in foundresses proceeds slowly during hibernation and early spring, becoming prominent in late spring and then falling sharply during the summer. This sequential pattern of ultrastructural modifications follows a functional, annual cycle. However, by comparing the subcellular changes in the gland with colonial development, it appears that secretory activity fits in with the specie's social cycle rather than merely following the seasons. The highest levels of secretory activity correspond to the early, critical breeding phases, while activity slows down with an increase in colony protection, based on both primary (passive) and secondary (active) defenses, with the emergence of the workers. These correlations suggest that the ectal mandibular gland secretory product in P. dominulus is involved in chemical nest defense. Copyright 2000 Wiley-Liss, Inc.