Some birds have blue feathers. This color is always achieved by interference of light waves, set up by a very sophisticated structure built into the feathers. From the Nature science update site, December 15, 1999. December 15, 1999. Mayflies and ancient atmospheres .
Modern mayflies look just the same as ancient mayflies.
This means, among other things, that Earth's atmosphere now must be much the same as it was in ancient times . Not very surprising, you say, and I agree. But it does allow us some defence against some of the far-out suggestions that have been made about ancient atmospheres. The same press release can also be found here . December 14, 1999.