Caterpillar-y action

Ned and Lyn noticed these caterpillars in action on Desert Hackberry plants (Celtis pallida) and turned to Fred for details.

Photo by Ned Harris 9/11/2015

Fred Heath writes:

Those are Snouts. Mary and I have been noticing them in the Desert Hackberries in Sabino over the last week. The caterpillars hanging down in “J” shape are about to pupate. They will shed their skin and the pupa will be underneath. I see that there are at least three pupas visible in this shot (two green and one gray green, the most obvious is the one in back, left of center, framed by two brown dead leaves).
Unlike Empress Leilia, which use only Desert Hackberry as a host plant, Snouts will use any Hackberry. I found a Snout caterpillars on the Net-Leaf Hackberry (Celtis reticulata) just above the dam the other day. Also, Snouts will sometimes decimate the leaves on the trees in an area and then have mass migrations to areas with more hackberry trees. The Empress Leilia on the other hand never seem to have these huge population surges.
Also of note, when I was photographing the Snout caterpillars and got too close or knocked a branch, they would drop on a silk thread, hang from the branch, and then slowly climb back up when the danger had passed. This is protective measure when approached by hungry birds and lizards. I’ve never known a butterfly caterpillar to do this.

 Thanks for another great post, Fred and Ned!