Thursday, July 29, 2010

Caterpillars with Attitude

Mourning Cloak- Linda Ellis
What could be more benign and peaceful than a caterpillar on a leaf.  After all, they are just eating machines which come out of an egg and fatten up constantly, out growing their skin in three or four molts.  After that, they get down to serious business, the remarkable conversion into a flying and sexually active butterfly or moth. 

Don't Touch My Babies
There is much more to the picture than that.  Many wasps lay their eggs on caterpillars.  Their larvae live in the cat, eventually emerging to form a pupa from which will emerge the adult wasp.  We previously showed a caterpillar parasitized by a wasp.  The video showed dramatically the emergence of larvae from the caterpillar's body with the caterpillar surviving the experience, at least temporarily.
It turns out in some cases that caterpillars even protect their tormentors.  A healthy passive caterpillar can turn into a raging maniac when it has been infested by larvae.  Unknown biological mechanisms may cause it to protect its new "offspring".  This well known phenomenon is shown in a video as a caterpillar actually defends the newborn wasps from a beetle.  It must think the little guys are its own. 

Back Off, Buddy
It also turns out that territorial caterpillars can send a message to the competition.  Some caterpillars can make sounds from hair-like structures on their legs.  This BBC story explains the mechanisms, a strategy not unlike a bull pawing the ground.  The video shows a cat starting a head-butting contest, then sending the scratching message, "Hey you!  Get off of my leaf!" and the competitor scrams.  Could this be the start of the evolution of road rage?

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