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For Insects, Spiders & Their Kin
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Photo#609830
Caterpillar - Tethida barda

Caterpillar - Tethida barda
Washington County, Ohio, USA
May 25, 2011
Small yellow caterpillar with black head and legs. "Lumpy" comes to mind. Found on box elder that had many galls on its leaves.

Moved

Looks like Tethida barda but
Looks like Tethida barda but T. barda feeds on ash.

 
Ash vs. boxelder
The two have somewhat similar leaves (and another name for boxelder is "ash-leaved maple")... If there are photos that show a whole leaf--or even what the galls looked like--that would help to confirm the plant ID.

 
Acer is not tasty
for sawflies larvae, as far as I know :) only a couple of species are known on Acer, but they definitely look different.
Let's imagine that we don't know the plant at all.
This larva belongs to Tenthredinidae -> Blennocampinae.
If this were a monochrome photograph, then larvae with a similar appearance should be looked for in several genera: Monophadnus, Stethomostus, Tomostethus, Tethida. But this specimen has a very distinctive coloration that matches Tethida barda.
It doesn't make sense to leave this in the undefined section.

However, if there are any objections, I am always ready to return it back.

Moved

Moved
Moved from ID Request.
Not related to the galls, but it's good that you noted the host plant.

sawfly
the sawfly people will tell you more.