Bug of the Month October 2016: Oslar’s Oakworm

Subject: Orange Caterpillar with Black Spikes
Location: Canyon de Chelly National Monument, Chinle, North Eastern AZ
September 30, 2016 11:09 am
Hello, I’m trying to identify this caterpillar (see photo) that we encountered at Canyon de Chelly. I have found some pictures of similar ones but nothing that looks exactly the same. Can you help?
Signature: Jeannette

Spiny Oakworm: Oslar's Oakworm
Spiny Oakworm: Oslar’s Oakworm

Dear Jeannette,
This is one of the Spiny Oakworms in the genus
Anisota, and because of your Arizona location, we are relatively certain it is Oslar’s Oakworm, Anisota oslari, which is pictured on BugGuide.  According to BugGuide:  “Larva – last instars are brick red” and “Larvae are known to feed on oaks, including Mexican blue oak (Quercus oblongifolia), scrub oak (Q. turbinella), and Emory oak (Q. emoryi).”  There are several related species in the genus found in eastern North America as well, and we frequently get images of mating Oakworm Moths  and newly emerged Oakworm Moths submitted to our site.  Since it is the first of the month, we are tagging your submission as our Bug of the Month for October 2016.

Thanks so much – it’s a beautiful caterpillar and I was frustrated trying to find out what it was. Your site is great!

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