Antibiotic Production: a Possible Function for the Metapleural Glands of Ants (Hymenoptera: Formicidae)

Abstract

Secretions from the metapleural gland of the Australian ant Myrmecia nigriscapa Roger were bioassayed against the spores of soil fungi that commonly occur where this ant nests. Four of the seven fungal species were nonentomogenous: Cladosporium resinae (Lindau) DeVries, Colletotrichum gloeosporioides (Penz.) Sacc, Gliocladium roseum Bain, and Mucor plumbeus Bon. Three were entomogenous: Beauveria bassiana Bals. Vuill., Paecilomyces lilacinus (Thorn.) Samson, and Metarhizium brunneum Petch. Metapleural secretions significantly reduced germination of the spores of all fungal species except M. brunneum. In this species, experimental and control spores germinated at approximately equal rates, but the secretions significantly reduced subsequent hyphal growth. These data, together with previously published experiments that show suppression of mycelial growth in eight other soil fungi by metapleural secretions, are consistent with the hypothesis that the metapleural gland is a source of antibiotic. The other social Hymenoptera, the bees and wasps, protect their juvenile stages in antibiotic-impregnated brood cells. By contrast, ants appear to utilize antibiotic secretions from the metapleural gland.