Subject: What is this bug/caterpillar living on Mesquite Tree?
Location: North Texas
July 29, 2012 11:57 am
There’s multiple bugs of this kind all over a growing mesquite tree. I’m not sure if it’s a caterpillar or what. Whenever we touch it with a stick it has what looks to be two tongues that come out of its head. Then I start smelling something. I don’t know if that smell comes from the bug. It’s summer here in the Northern part of Texas.
Signature: Robert

Giant Swallowtail Caterpillar

Hi Robert,
This caterpillar is aGiant Swallowtail Caterpillar and it will eventually metamorphose into a beautiful adult Giant Swallowtail.  Giant Swallowtail Caterpillars are frequently found feeding on the leaves of orange trees, giving the caterpillars the common name Orange Dog.  The tongue you mention is a scent organ called an osmeterium and it functions to discourage predators by releasing a smell that could be described as unpleasant.  We were confused by your claim that these caterpillars are feeding on mesquite, and the plant in your photo does not resemble mesquite which you can view on Desert USA.  We learned on BugGuide that Giant Swallowtail caterpillars feed on the leaves of Prickly Ash, and upon doing some research, we found photos of Prickly Ash
on the North Carolina Wildflowers, Shrubs & Trees website, and they appear to match the plant in your photo.  We believe your caterpillars are feeding on Prickly Ash, not Mesquite.

Location: Texas

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