Ed Yong writes: Hurbert Walter Simmonds had only been in Fiji for a year before he was appointed as Government Entomologist in 1920. It was an unusual role, but an important one. The island was repeatedly threatened by agricultural pests, and so Simmonds would spend the next 46 years searching for predators and parasites that could bring these crop-destroyers to heel.

In his downtime, he collected butterflies. There are thousands of species in Fiji, and the blue moon butterfly (Hypolimnas bolina) is among the most beautiful of them. The name comes from the males, whose black wings have three pairs of bright white spots, encircled by blue iridescence. They are stunning, and all males look the same. The females are more varied: they are clothed in a wide range of spots, stripes and hues, many of which mimic other local butterflies. Simmonds wanted to know how these patterns are inherited, so he started capturing and breeding the insects.

That’s when he noticed that most of the females only gave birth to females.

Some 90 percent of them would produce all-female broods. They laid large clutches of eggs and around half the embryos died — presumably, the male ones. Simmonds didn’t know why. [Continue reading…]