Here’s another cohabitant I frequently turn up in fire ant nests. These tiny black beetles belong to one of the largest and most diverse beetle families, Scarabaeidae, the scarab beetles. They fool their ant hosts by coating themselves in chemicals that cause them to smell and taste like ants. When I went to research more information on these interesting little beetles I could find very few scientific studies addressing them. These beetles, Martineziana dutertrei, seem to function primarily as parasites of the ant colonies that host them, stealing prey and other nutrients, and even eating ant larvae.
Martineziana dutertrei was apparently introduced to the United States at some point during the introduction of its host species, either the red imported fire ant, Solenopsis invicta, or the black imported fire ant, Solenopsis richteri. This beetle species are now also found in the nests of a native relative of the infamous imported fire ants, the tropical fire ant Solenopsis geminata, where the beetles have evidently somewhat displaced their own native relative.
Reference: Wojcik, et al. Ins. Soc. 38:273-281 (1991)