Large Spotted Acrea Caterpillars bothered by Tachinid Fly

Location: Kinshasa, Congo
January 2, 2012
Thanks for the additional information on the caterpillars.  We went back yesterday to the same location where we found the Acraea zetes menippe and saw a whole lot more caterpillars.  There were quite a few climbing up a certain plant and regrouping in clumps of 5-10 individuals. We photographed a group on one of the leaves they were eating and filmed some interesting behavior.   Where the caterpillars were in a group, they seemed to react to flies.  As flies approached, they all started flailing their heads in the air.  We tried to reproduce the behavior by tapping on the leaf and blowing on the caterpillars but they only seemed to have that reaction to approaching flies.  The video can be viewed here:
A few pictures of the group on the leaf they were feeding on and one of a solitary caterpillar found nearby also attached.
Thanks again
Katy and her Dad

January 4, 2012
Keith and Daniel,
We hope you had a great New Year celebration.  We are intrigued to get your opinion on the behavior witnessed by a group of Acraea zetes caterpillars that we saw a few days ago.  We sent an email will additional photos of the caterpillars on one of their food source leaves but the internet connection has been very problematic.  Please confirm receipt or we can send again, one image at a time.   The video can be viewed here:
Katy and Nick

Acraea Caterpillars and Tachinid Fly

Keith Wolfe responds
Katy, Dad, and Daniel,
Let’s pretend for a minute that these seven caterpillars are the five of us (mustn’t forget Mom) and two friends having a picnic, when suddenly a never-before-seen ginormous (relative to our size) fly starts buzzing around.  Bugman and I would probably be snapping photos and otherwise documenting the encounter for a scientific paper, but fast forward 1000 generations, when by now natural selection has honed our behavior to instinctively recognize these tachinid flies ( as mortal enemies — parasitoids whose reproductive strategy is to lay eggs inside our soft, slow-moving bodies so that their ravenous offspring will survive at our expense.  With that in mind, we too would be wildly flailing our heads, arms, and bodies, along with regurgitating bitter intestinal juices as an added deterrent.
Blue skies,

Thanks Keith,
That is great information and it explains why the caterpillars were not phased by tapping on the leaf or blowing on them but when they heard the flies nearby, they went into hyperdrive with the flailing.
Thanks again!

January 12, 2012
Dear Katy, her Dad and Keith,
Thanks so much for supplying additional photographs and a wonderful explanation of the parasitic habits of the Tachinid Flies with regards to Caterpillars.  We have been on holiday for the past week and just returned, which we hope explains our lack of input in this posting.

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