Evidence, using radioactive phosphorus, of interspecific food exchange in ants

Abstract

MEMBERS of many ant species exchange fluid foods within the colony^1–4. Similar exchange between social symbionts, living as “slaves”⁵ or “guests”⁶ and their hosts, is also documented¹. However, in non-symbiotic species, found in the same habitat or in distinctly different habitats, this phenomenon is usually overlooked. We document here that the food-transporting worker ant of one species offered carbohydrate food to the aggressive worker ants of another as a means of suppressing aggression in the latter, as in appeasement displays in higher animals. The workers of the aggressive red fire ant species, Solenopsis invicta, introduced into the southern United States in the 1930s but comparatively recently named⁷, were invariably offered regurgitated fluids by indigenous species S. geminata and Pheidole dentata which had been fed earlier with ³²P-labelled 20% sucrose solution.