Rove beetles are an ancient family, primarily distinguished by a short shard (wing cover) that typically leaves over half their abdomens exposed. Emerging over 200 million years ago during the Triassic, rove is the most specious family of beetle, with over 63,000 species in thousands of genera. Rove are roving in every biome where beetles live.
Most rove are invertebrate predators, especially of other insects. They often live in obscure places: forest leaf litter, under stones, and around freshwater margins. Around 400 species reside on ocean shores that are submerged at high tide.
A social insect colony is an energy-packed resource with lots of different niches. If you manage to get in, the payoff is very high. ~ American evolutionary biologist Daniel Kronauer
Army ants are notoriously fierce. They specialize in coordinated mass attacks. Yet within the bivouacs of all 340 known species of army ant live tiny rove beetles, surreptitiously stealing food from their unsuspecting hosts.
These flea-sized parasites lost their beetleness to look, smell, and behave so much like ants that they can pilfer food stores or eat ant larvae with impunity. This remarkable feat of evolutionary deception independently evolved dozens of times.
The common ancestor of the parasitic lineage of rove beetles evolved a gland at the tip of the abdomen that can squirt noxious compounds – quinones – at attackers. This was a useful head start.
It’s a pre-adaptation that allows you to undergo some extreme adaptations. ~ American entomologist Joseph Parker
Since then, parasitic beetles evolved variant glands with new functions. One group sprays ant alarm pheromones that send would-be attackers scattering. Another secretes chemicals that ants use to recognize colony mates.
With the help of a raft of morphological features – including narrowed waists, longer legs, antennae like ants, and even an antlike gait – interloping rove beetles persuasively fool their fearsome hosts into feeding, protecting, and transporting them.