Strange White Caterpillar from Oil City Pennsylvania
Hello Bugman!
I emailed you last week but just realized that you requested the location of the bugs found. I am resending this letter in hopes that you can help me identify the caterpillar we found in our backyard. First, I must say I love your website and check it regularly. Recently my fiance and I found this caterpillar (the first two pictures) on a small tree in our backyard in Oil City (Northeastern) Pennsylvania. There were 4 of them and I cannot seem to find it anywhere on your website or the rest of the Internet. I was hoping you could tell us what it is. The third picture I believe is the Gypsy Moth Caterpillar but just wanted to double check. Thank you for your help in advance. Keep up the great website!!! Thank you,
Shannon G.

Hi Shannon,
Your white caterpillar is, we believe, infected with Fungus that will probably kill it. It is difficult to determine the species of caterpillar from your photo. BugGuide has a big section on Fungus riddled Flies, but not one for caterpillars. In trying to research Fungus attacking Caterpillars, we found references to a fungus, Entomophaga maimaiga, that is host specific on Gypsy Moth Caterpillars, but it does not resemble the Fungus in the image you have provided. The Gypsy Moth Fungus, Entomophaga maimaiga, is an important biological control of this invasive species, and you can read more on the Country Gardener. The Cornell University Biological Control website has a photo of an infected Gypsy Moth Caterpillar. Your second caterpillar is a Gypsy Moth Caterpillar.

Correction: (07/29/2008) Strange White Caterpillar from Oil City Pennsylvania
This looks a lot like the “Butternut Wooly Worm” images on bugguide. Found them while trying to see if the fly/wasp I sent matches any of their sawflies.

Thanks for the correction Audrey. Seems someone on BugGuide also entertained the fungus idea. The Butternut Wooly Worm is actually a Sawfly, Eriocampa juglandis.

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