Species: Melissotarsus insularis and three other Melissotarsus species
Habitat: Down on the farm under the bark of African trees, particularly in Madagascar.
Lots of ants practice a rudimentary form of agriculture. Some are gardeners, gathering leaf fragments on which they cultivate a crop of tasty fungus. Others are dairymaids, “milking” the sweet excretion known as honeydew from aphids, scale insects and other related insects.
But the Melissotarsus ants of continental Africa and Madagascar are special. If biologists’ best guess proves correct, these ants raise their insect herds for meat, not milk – the first example of meat farmers other than humans. And that’s not all. The insects they cultivate may be the best example of true domestication outside of our crop plants.
You have to know what you’re looking for to even see Melissotarsus. The ants – barely 3 millimeters long – live most of their lives within the intricate gallery systems they excavate in and under the bark of trees. They’re such committed burrowers that their second pair of legs points up, not down, so they can get a foothold in the tunnel roof as well as the floor. They share their galleries with several species of armored scale insects, so-called because most species secrete a tough, waxy scale that covers and protects them.
But the ants’ charges aren’t paying for their keep in the usual way, with honeydew. In fact, they apparently lack a complete gut and thus are incapable of making the stuff. Nor are the ants nibbling at the waxy scale – the scale insects tended by the ants, despite their name, have no scale, and some even lack the wax glands needed to produce it. “Armored scales just don’t seem to be equipped to produce an exudate that’s enough to satisfy an ant,” says Scott Schneider, an entomologist at the University of Massachusetts at Amherst.