THE colourful scales on a butterfly鈥檚 wings evolved from humble
origins鈥攖he tiny hairs on flies and other insects.
Biologists have long suspected that scales on butterfly wings evolved from
these 鈥渟ensory bristles鈥�, because they attach to the body through similar socket
structures.
To test this at a genetic level, Sean Carroll of the University of Wisconsin
in Madison and his colleagues looked at a bristle gene called
achaete-scute in fruit flies. Butterflies also carry this gene. The team
showed that in the buckeye butterfly Precis coenia, the gene switched
on in socket and scale cells at the beginning of wing development (Current
Biology, vol 8, p 807).
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鈥淭his fits well with how we think evolution makes something novel,鈥� says
Carroll. 鈥淚t co-opts structures it already has and starts innovating.鈥�