Life Among the Ants

Here's a neat little guy that I had never heard of before yesterday:

Eastern Ant Cricket (Myrmecophilus pergandei),
Gander Mt. FP, Lake Co, IL  4/11/2014

This is an Eastern Ant Cricket (Myrmecophilus pergandei). I found this one living in a nest of small ants, possibly Lasius alienus. Apparently they normally live in ant nests, eating food gathered by the ants. I've seen this lifestyle, often termed inquiline, described as both kleptoparasitism and commensalism.

This particular species is a generalist, living with a number of different ant species, while others in the genus are more specialized. (None of the specialized species occur in the US except for M. americanus, which despite the name is an Old World species that occurs with the introduced Longhorn Crazy Ant (Paratrechina longicornis) (1,2)). Specialists often interact directly with their host species. (3) Since ant interactions are chemically mediated, it's apparent that these crickets mimic their host's chemical signals.

Among the ants, those signals are species-specific, which means that a specialist will have considerable trouble mimicking more than one species. Generalists avoid this problem mostly by avoiding the ants -- a technique that likely reduces their foraging success and probably leads to them being killed or ejected from the nest occasionally. On the other hand, generalists are frequently able to live without the ants - specialists typically aren't. (3) (How they reach new nests in the first place is, I'm sure, a fascinating topic.)

These two end points are easy to understand. The pathways from generalist to specialist are often difficult to untangle, but in this case we have what looks like an example of the early stages: a species (M. tetramorii from Japan) that is a host specialist but doesn't rely on chemical signals, and in fact does routinely suffer attacks from the host ants. (4)

(1) Wetterer, J. K., & Hugel, S. (2014). First North American Records of the Old World Ant Cricket Myrmecophilus americanus (Orthoptera, Myrmecophilidae).Florida Entomologist, 97(1), 126-129.

(2) Hebard, M. (1920). A Revision of the North American Species of the Genus Myrmecophila (Orthoptera; Gryllidae; Myrmecophilinae). Transactions of the American Entomological Society, 91-111.

(3) Komatsu, T., Maruyama, M., & Itino, T. (2009). Behavioral differences between two ant cricket species in Nansei Islands: host-specialist versus host-generalist. Insectes sociaux, 56(4), 389-396.

(4) Itino, T. (2013). Nonintegrated Host Association of Myrmecophilus tetramorii, a Specialist Myrmecophilous Ant Cricket (Orthoptera: Myrmecophilidae). Psyche: A Journal of Entomology, 2013.