Carl Zimmer in his blog, The Loom:
Like many parasites, a species of bacteria called Wolbachia takes charge of its own fate. Wolbachia can only survive inside the cells of its hosts–invertebrates such as this lovely common eggfly. This way of life limits Wolbachia’s opportunities for long-term survival. If Wolbachia lives inside a female insect, it can infect her eggs. When those eggs hatch and mature into adult insects, they will be infected by Wolbachia as well. But if Wolbachia should find itself in a male, it has reached a dead end. It cannot infect sperm cells, and thus it has no escape from a male host. When a male host dies, Wolbachia dies as well.
Wolbachia’s solution: kill the males before they kill you.