# Novel Worker‐Like Behavior Observed in Gynes of the Social Parasite Tetramorium microgyna

## TL;DR

Scientists observed a type of socially parasitic ant performing worker-like tasks, which may hint at evolutionary remnants of non-parasitic behavior.

## Contribution

First observation of inquiline gynes performing worker tasks for their host colony.

## Key findings

- Tetramorium microgyna gynes were seen excavating soil and maintaining host nests.
- All participating gynes were unmated with ~6 ovarioles, suggesting a non-reproductive role.
- The behavior may reflect an ancestral trait from a non-parasitic past.

## Abstract

Socially parasitic ants increase their own fitness by exploiting the labor and resources of non‐kin ant colonies. Here, we report a novel worker‐like behavior observed in an African workerless inquiline,
Tetramorium microgyna
, a parasite of
Tetramorium sericeiventre
and
Tetramorium sepositum
. We observed several
T. microgyna
gynes excavating soil and performing nest maintenance tasks at the entrance of an established
T. sericeiventre
host colony. We photographed this event in nature, then dissected
T. microgyna
gynes to establish mating status and reproductive capacity. All
T. microgyna
gynes that participated in excavation behaviors were unmated, with ~6 ovarioles. We hypothesize nest excavation by inquilines represents an artifact of a non‐parasitic past, where gynes that fail to mate and disperse remain in their natal colony and assume a secondary, but still mutually beneficial worker‐like role. While nest excavation by socially parasitic foundresses could be an artifact of an ancestral behavioral repertoire associated with independent colony founding, this possibility is unlikely, because the behavior occurred in the presence of a robust worker population. While helping behavior in post‐reproductive inquilines does not increase personal fitness, it also does not reduce it, and may be maintained through relaxed selection. Although host and parasite gynes are morphologically distinct, a third possibility is that putative
T. microgyna
parasites are actually microgynes of their ‘host’ species. Socially parasitic ants are rarely found and poorly studied compared to their non‐parasitic counterparts. Our findings provide insights into how selection may act on developmental and behavioral programs during the evolution of social parasites from non‐parasitic ancestors.

Our article reports, to our knowledge, the first observations of inquiline gynes performing worker tasks for their host colony. We dissected these gynes to establish that they were all unmated. We hypothesize that nest excavation by social parasites represents an artifact of a non‐parasitic past.