Guest post by Joseph Parker, Coleopterist, Columbia University.
If you’ve ever been fortunate enough to walk through a rainforest, you’ll probably have noticed huge numbers of ants patrolling the ground at your feet. Ants dominate forest environments, dismembering other arthropods, harvesting honeydew from plant sucking bugs, and waging war on neighbouring colonies.
But amongst the ants exists another, far more poorly known group of creatures… a group of beetles called Pselaphinae (SEH-LA-FIN-EE). In terms of species richness they rival—and may even surpass—ants. These beetles are remarkable, being one of the most morphologically diverse groups of organisms out there, with a seemingly endless range of bizarre body forms.
What is more, Pselaphinae are one of the few groups of organisms which have evolved the capacity to exploit ants, living inside their colonies where they feed on the ant brood.
In some cases, the beetles are so dependent on ants that they can no longer exist out the nest. The ants carry them around and feed them liquid food, and the beetles even exude substances from brush-like structures on which the ants feed. Some of these species rank among the strangest-looking insects known: they can be eyeless and wingless, their body and antennal segments have fused together to make rigid plate and club-like structures, and they’re covered in secretory glands which exude mysterious chemicals.
The mechanisms these beetles use to dupe the ants are largely unknown, but likely involve chemical and perhaps physical and behavioural mimicry. How they disperse to find mates is also unclear, but one possibility is that they attach phoretically to dispersing queen ants during the nuptial flight.
Over 9000 species of Pselaphinae have already been described, and still many tens of thousands more await description. A giant backlog of new species sits in museums around the world, and new species and genera are continually added with every tropical expedition. Unfortunately, probably because of their minute size (most are 1-3mm long), few entomologists actively study them, and the group epitomizes the “vast, neglected group of insects” problem which pervades taxonomy.
To give these remarkable creatures some much needed attention, a crowd-funding project has been set up at PetriDish.org to reconstruct their evolutionary relationships and where you can learn more about them.
Thank you to Taku Shimada of antroom.jp, for kindly allowing the use of his photographs.