Butterflies Dupe Ants, Trigger "Smell" Race

I had a bunch of hits on my antroom newsfeeder about a very interesting new paper in this week's Science, but I liked the blog entry from Zooillogix the best, so here it is:

A new scientific paper has shown a strange, deceptive adaptation in the Maculinea butterflies of North Western Europe--an adaptation that has caused a genetic race between the butterflies and many different species of ants. The butterflies' caterpillar larvae emit a powerful smell that tricks the ants into believing that they are in fact ant larvae. The ants then...

...carry the larvae back to their secret lairs, and feed them. Just like the famed cuckoo birds, the larvae trick the ants so effectively that the ants give up on taking care of their own brood to focus exclusively on the caterpillars.

In response to this invasion, however, ants from colonies that have been "parasited" by the butterflies have evolved to have a different odor than the butterflies, and thus are able to recognize the caterpillars as frauds.

In their research David Nash, Jacobus Boomsma and others from the Centre for Social Evolution (CSE) at the University of Copenhagen show that colonies of ants which developed a resistance (a different smell) and then interbred with colonies who had not been exposed to the parasites lost their resistance as the genes were diluted. Of course, they then fell victim to the Maculinea butterflies again.