Yesterday during my class at FEEL, I asked participants to go out in the corn and soybean plots and find pests. It didn’t take too long to find a few plants loaded with soybean aphid. It was the largest natural colonies I have seen this summer (potentially exciting for my research but not great for farmers). They also found potato leafhopper, green cloverworm, Japanese beetle and corn rootworm. Not too surprising given its mid-July, and soybeans are blooming and corn is silking.
But one guy (let’s call him Todd) brought me a funky caterpillar that I’ve never seen before. So like a good entomologist, I brought it back to the lab for identification. Dr. Lewis is one of my go-to diagnosticians in our department. He recognized it as a geometrid species, commonly known as inchworms. There are about 1,400 geometrid moths in North America alone – so not that unusual. Then he used some butterfly and moth references to further narrow it down. We both agreed it looked like Nematocampa resistaria, or a common name of spanworm moth.
This species has a variable body color, but tends to be brown and mottled with dark spots to blend into the background. This caterpillar gets to be 3/4ʺ long, and has one pair of prolegs and four filaments. The filaments on the top of the abdomen are like flexible tentacles. They filled up with fluid and waved around when I touched them (yes, I had to touch them!). I am guessing it is a defense mechanism.
Normally this filament bearer likes to be on low-growing, woody plants (e.g., pine, hemlock, fir, larch, and spruce). Of course, soybean was the wrong place for this filament bearer and not considered an economic pest. But I took and few pictures to share anyway. Thanks, “Todd” for finding this treasure!