An ant that protects herself with… um… butt foam

I’ve left you hanging long enough. Here is what Thursday’s mystery ant, an Asian Pachycondyla, does when bothered. She sprays foam from her venom gland.

This big tropical ant is a new addition to Andy Suarez’s University of Illinois research bestiary. A colony was collected by the recent multi-institutional Cambodian expedition for studies of ant venom chemistry, among other projects. A 1981 paper by Maschwitz et al describes the unusual defensive behavior:

When disturbed, two species of Malayan Pachycondyla release foam threads more than 10 cm in length or foam piles. The source of the proteinaceous foam is the enlarged venom gland, which is probably frothed up by air from the spiracles of the spiracular plates. The Dufour’s gland normally producing hydrocarbons in stinging ants is atrophied. Therefore, absence of the Dufour’s gland could be essential to the foaming ability, since the lipophilic hydrocarbons inhibit froth production in protein solutions. The release of foam is a mechanically acting defense mechanism, which is very effective against small mass-attacking ants. Pachycondyla species are also able to sting effectively.

I can vouch for their ability to sting effectively, too*.

*no ants were harmed in the making of this post, and the colony was rewarded for their participation with several fat crickets. I, on the other hand, discovered that the ants have a more conventional defense, too: a good, old-fashioned stinger.

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source: Maschwitz U, Jessen K, Maschwitz E (1981) Foaming in Pachycondyla: a new defense mechanism in ants. Behav Ecol. Sociobiol 9:79-81.