Social parasitism involving ants of different subfamilies: Polyrhachis lama (Formicinae) an obligatory inquiline of Diacamma sp. (Ponerinae) in Java

Summary:

Socially parasitic ants usually live in dependence on closely related host species. An instance of obligatory social parasitism by a formicine ant, Polyrhachis lama, on colonies of a ponerine ant, Diacamma sp., from Java is described. Reproductive females of both species coexist in the nests, in which one gamergate queen of the Diacamma host is always found. Dealate females (gynomorphs) of the parasite species are rare (7 in a total of 48 mixed colonies), and only 2 out of 4 dissected individuals were inseminated. Parasitized nests comprise a very low number of P. lama "workers" (ergatomorphs), between one and rarely more than 10 (Table 2). Both virgin and mated dealate gynomorphs, and also the ergatomorphs, which always lack a spermatheca, are fully reproductive, probably having males, ergatomorphs and alate gynomorphs as offspring. The broods of host and parasite are mixed, and the Diacamma workers take over, at least in part, the brood care for the parasite. Polyrhachis lama is very rarely found outside the nests and its ergatomorphs do not engage in foraging. Parasitizing distantly related species may be more common in ants, particularly in the genus Polyrhachis, though the few reported instances are anecdotal. We suggest an evolutionary origin of this kind of parasitism from mimetic relations between Polyrhachis lama and the pugnacious Diacamma species.