This is a repost of an original Bug Chicks article on Science Friday.

Back in March, we traveled to the Soltis Center in Costa Rica to film material for Texas A&M Videos.  Each night for a week, we trekked into the rain forest to film and photograph anything with an exoskeleton we could find. The first night we ran across an amblypygid, also known as a tailless whip scorpion or whipspider. These dorsoventrally flattened animals are arachnids, but are not true spiders or scorpions.  They possess no venom and are very gentle (if you’re a human). They look like they have long whip-like antennae, however those are the first pair of legs. The tarsal segments are elongate and they whip out and feel for prey.  Once a potential prey animal has been detected, the amblypygid lunges forward with outstretched pedipalps.  The pedipalps (we like to think of them as mouth-hands) have spines on their inner surfaces that pierce into crawling prey like crickets and cockroaches.
On the third night, we came across this interesting individual. It’s an adult amblypygid, like the one above, but notice the mass on its back. Some people might think the objects on the back of the whipspider are eggs.  But amblypygids carry their eggs underneath their abdomen. These are insect pupae, from a parasitoid insect.  A parasitoid is an insect that lays its eggs on or in a host animal. They almost always kill the host.
Flies in the family Chloropidae emerged from these pupae.  The adult female fly probably laid her eggs onto the eggsac of the amblypygid and when the larvae hatched they ate the whipspider eggs.  To pupate, the larvae climbed up onto the back of the whipspider.  So the adult amblypygid will live but her progeny did not survive.
It always exciting to find an animal that’s been a victim of a parasitoid. As we dug into the literature, we could only find one other reference of this behavior of amblypygid egg parasitism (Vicquez et al 2009).
We went a step further to see if anyone had posted pictures of this online.  We only found one picture, from Stuart Longhorn on Flickr, taken in Honduras.  We will admit, it’s pretty incredible:


Have you seen something like this on your travels?  We’d love to know.  Drop us a comment!


Viquez, C. Armas, L. F. de. 2009. Parasitism on whip spider eggs (Arachnida: Amblypygi) by Chloropidae flies (Insecta: Diptera). Boletin de la S.E.A. 45: 541-542.