by Merry — Wol­bachia have caused one of the great pan­demics in the his­tory of life. They in­fect at least 20% of the species of arthro­pods – which adds up to about 10^6 species – as well as other in­ver­te­brate hosts. And they have done this us­ing only ma­ter­nal (ver­ti­cal) trans­mis­sion to in­fect their next host. Ma­ter­nal trans­mis­sion is...