Spite: Evolution Finally Gets Nasty

Courtesy Michael R. Strand

Some have described spiteful behavior in Copidosoma floridanum. These wasps lay their eggs in the egg of moth, Trichoplusia ni. The host larva as a fourth instar is shown at top. Copidosoma fight for resources as they consume the caterpillar. Some differentiate into sterile soldiers foregoing reproduction to preferentially kill less-related larvae. In the so-called mummy (middle) the outlines of reproductive larvae are visible as they pupate. Eventually, they emerge as adults (bottom). Soldier larvae, in contrast, die inside the mummy.

The body of a caterpillar is the site of both a great feast and a gruesome familial struggle. But unlike even the most dys-functional holiday dinners, this fight for food erupts into bloodbath, with sisters killing sisters and brothers alike. The slaughter, as damaging to killer as to killed, exemplifies an ugly facet of evolution – the role of spite.

Partaking in this grisly feast ...