What is the creature on the left? If you said, “cockroach”, give yourself a lump of coal. But if you said, “termite”, give yourself a PEZ dispenser with your favorite cartoon character. It is in fact a specimen of Mastotermes darwiniensis, a large and primitive termite that lives in Australia (they get all the cool critters). It looks like a roach because termites evolved from roaches, and this particular genus contains primitive members that still resemble their roach cousins in many respects. On the flip-side, roaches of the wood-eating genus Cryptocercus have many termite-like features, including obligate gut flora and parental care of nymphs. The termites that we’re familiar with – the little white things that eat houses – are simply the nymph stage of an otherwise roach-like insect, and Cryptocercus nymphs look an awful lot like termites themselves.
A biologist going by the name of “Mr. Darwin” has a great post up about the evolution of termites from roaches, and the various lines of morphological, molecular, and fossil evidence we have. And there is a cool picture of cute little Cryptocercus nymphs feeding from their mommy’s anal secretions. Go check it out.