Degenerate slave-makers, but nevertheless slave-makers? Host worker relatedness in the ant Myrmoxenus kraussei.

Socially parasitic ants of the formicoxenine genus Myrmoxenus exhibit considerable diversity in colony structure and life history. While some species are active slave-makers with many workers and others are workerless 'murder-parasites,' Myrmoxenus kraussei is considered as a 'degenerate slave-maker' because of its very low worker numbers. Here, we document that Temnothorax recedens host workers in single colonies of M. kraussei from Lago di Garda, Italy, exhibit significantly more genetic diversity than workers in unparasitized colonies. This raises the possibility that, despite its low worker numbers, M. kraussei may actively engage in slave raids in nature.