Friday, January 8, 2010

What's this? It's Paussinae.

This is Platyrhopalopsis, a Carabid (ground beetle) from Thailand. Those radar dishes on the top of its head are the antenna.

Although the exact host is unknown, this beetle almost certainly lives in an ant nest. This lifestyle is known as myrmecophily, and you wouldn't believe all the crazy species that make a living this way. Paussinae may be using those antenna to communicate with their ant hosts, but beetles in this group are generally collected only at light traps; so most of their natural history remains a mystery. Some researchers have reported ants using the antenna as handles to relocate the beetles. The plate below shows the astounding diversity of antenal morphology in the subfamily. It's a great example of 19th century naturalist drawing, by John Obadiah Westwood, 1837. 

Primitive Paussinae generally have standard mouthparts and thick exoskeletons, while more derived species are lighter and have spoon shaped mouthparts specially adapted to receive regurgitated food directly from ants. All members of the group can mix quinones and gases to produce an explosive self defense, evolutionarily independent of but extremely similar to the famous Bombardier beetles, a different lineage of the Carabidae.



  1. That's absolutely ridiculous. It looks like the disc is just one huge flattened segment. The nerve architecture going through that thing must be crazy.

    Do they get collected at light traps year round or just in bursts, as if they are out en masse for mating?

  2. Hey Jess!

    I think they get collected mainly during the summer, but dissected females display ovaries in all stages of development. I found this on the antenna:

    In the myrmecophilous genus Paussus, these structures are composed of three joints: scape, pedicel and a wide third joint, the “antennal club”, resulting from the fusion of antennomeres A3–A11 (flagellum). The antennal club shows an exceptional glandular activity, with the presence of pores mostly crowded in special hairless cuticular areas, surrounding the base of single setae, grouped at the base of tufts of setae, or positioned inside deep pockets that store the secretions, with filiform material arising from them.

    Fine structure of the antennal glands of the ant nest beetle Paussus favieri (2009)

    Another great paper is: A review of myrmecophily in ant nest beetles (Coleoptera: Carabidae: Paussinae): linking early observations with recent findings (2005).