Wednesday, July 6, 2011

Green-striped Mapleworm

I found some green-striped mapleworm (Dryocampa rubicunda) caterpillars on a young maple tree.
 The caterpillars were making quick work of the maple's leaves. 
The green-striped mapleworm caterpillars are not very cute, with their black "horns" and rows of studs, but the adult is a very attractive moth.
Rosy Maple Moth, Dryocampa rubicunda
The green-striped mapleworms turn into the rosy maple moths.
 This caterpillar has just shed its skin.

The photo above shows some of the "studs".
   The green-striped mapleworms start out in a group, or gregariously.  Later they migrate to other leaves and form less of a group.  That means there were quite a number of these caterpillars in the vicinity.  I noticed several interesting activities among that group.
   First, I saw several leaves with stains like the ones in the photo below.
   That looks like the caterpillar recently encountered some kind of enemy and was deploying some of its defensive responses.  Maybe a parasitic wasp (I saw a few flying around them) or a predatory beetle was there just before I was.  Anyway, the marks on the leaf make me think the caterpillar was defensively thrashing around and regurgitating at the same time.
   I recreated the scene in the photo below.
   When I "pinched" the caterpillar it swung its head to the side and regurgitated that black "tobacco juice".  Then it swung its head back the other way still spitting.  Those are some of the caterpillar's defensive maneuvers.
   Another interesting action I saw among the caterpillars was what I think was some kind of defensive signaling.  When I disturbed a caterpillar (like bump the leaf), it would rear up like this one pictured below.
Then the caterpillar would rhythmically jerk its head slightly from side to side which would shake the leaf it was on.  Soon other nearby caterpillares were doing the same thing.  Thus I assumed this was a defensive response and the caterpillars were communicating danger either through the vibrations or some other means.
   I'd rather see those sherbert-colored rosy maple moths than those tobacco spitting, stud covered, horned, creepy crawlies.

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