Common Sootywing (Pholisora catullus) Life History

Probable egg, 3-11-09

First caterpillar, 3-22-09





Second caterpillar, 4-10-09

4-12-09, just before (or after?) shedding skin to form last instar

Third caterpillar, ready to pupate, 4-3-09

4-4-09, pupating

4-11-09, fully formed pupa

Fresh Common Sootywing, 4-13-09

This life history is assembled from photographs of three caterpillars. I observed a Common Sootywing ovipositing on Pitseed Goosefoot, Chenopodium berlandieri, on March 11, 2009.  A search of the plant turned up two brown eggs, which I suppose to be from the Sootywing. I decided to monitor rather than collect these eggs. On March 22, I found a small caterpillar on the plant, probably the first instar. This caterpillar was checked and photographed until, unfortunately, it disappeared. I collected two caterpillars during the next week; these were used to fill out the life history.

The caterpillars make a shelter by rolling up a leaf on the host plant, or by sewing a couple of smaller leaves together. They also pupate in these shelters. Spiders are common on these plants and form similar shelters. I suspect that the pupa with its false eyes and whiskers is a protective adaptation: to me it looks like the face of a spider, which might scare away a potential predator that looks into the rolled up leaf.

Later in the spring I began checking for more caterpillars. I found a few shelters, but instead of caterpillars I found what appeared to be parasitized remains. I will try to follow up on this as the opportunity is presented; meanwhile, if anyone is aware of a wasp (or similar creature) that parasitizes these caterpillars, I would appreciate being informed.