Wolbachia doesn’t just infect the blue moon; it’s also found in some 40 percent of species of insects and arthropods, as well as other animals like parasitic nematode worms. Scientists still disagree about whether the various lineages (or “supergroups”) should be classified as a single species or as many separate ones. But however you cut it, Wolbachia is everywhere.
As I’ve written in The Atlantic before, many scientists are trying to use this omnipresent microbe to stop important tropical diseases like dengue fever, Zika, and elephantiasis. Others, like Hurst, are studying it for its own sake, including the extraordinary ways in which it manipulates its hosts. Sometimes, as in the blue moon butterfly, it kills males outright. In other hosts, it can transform males into females, or even turn females into cloners that can reproduce asexually without needing males at all.