ScienceShot: Sex and the Single Insect

The female scale insect (Icerya purchasi) is an independent woman. She carries her own sperm—harbored in tissue passed down through the generations—so she doesn't need a male to have her babies. Scientists have long believed that this unique procreation strategy—scale insects are the only hermaphroditic insects and the only animal in the world to employ such a sperm packet—is harmful to the female, as the "sperm packet" consumes resources in her body that she could otherwise devote to making more eggs. But a new analysis, to be published next month in The American Naturalist, suggests that there are advantages to being single. By using her own sperm instead of mating with a male, the female keeps all of her family's genes in her bloodline. The strategy, however, may not be so good for the few males left in scale insect populations: They're becoming obsolete and may eventually go extinct.