Yes, the shiny purple-green creature above and the sky-blue one below are cockroaches. But they do not at all want to live in your house.
Among the world’s more than 4,600 or so roach species, “people have tended to concentrate on just the boring pest species,” says George Beccaloni, curator of cockroaches and their relatives at the Natural History Museum in London. That’s only about 30 annoying species, roughly the same proportion of pests as found among the 5,500 or so known mammal species. Yet people don’t squeal, “Mammals, ewww.”
A few bad roaches spoil the image of the whole Blattodea order. Most people, Beccaloni laments, “don’t know anything about the other very attractive and interesting cockroaches that are out there.”
Some roaches are downright beautiful. One Melyroidea pretends to be a noxious beetle with a cherry-red head and slim metallic green back. Another mimic, a plump little button of a Prosoplecta in the Philippines, is round and red as a ladybug. To fit full roach wings under its dome, it has evolved extreme origami.Roaches offer their own safari thrills, too. Beccaloni has gone to Madagascar to study the hissing cockroaches, unique to the island just as lemurs are. Males grow two horns and “fight each other like rams,” he says.
He has also visited Australia’s rhinoceros cockroaches, which can weigh more than a house mouse. Australians finding them lumbering across a highway after a rain have mistaken them for baby turtles. A local naturalist (who promoted his region as home of the world’s largest roaches and commissioned souvenir teaspoons decorated with them) went digging with Beccaloni to explore the kinds of burrow a mated pair lives in, sometimes a meter deep.
Also, some cockroaches can be caring moms. Instead of just laying eggs and leaving, a Diploptera roach carries her developing embryos in an internal brood sac where the walls produce an insect form of mother’s milk. A Perisphaerus female from Malaysia that lived with Beccaloni as a pet carried youngsters clinging to her underparts. It was hard to see what they were doing, but Beccaloni says that the young’s mouthparts, shaped like little drinking straws, were sized to fit into openings at the top of four of mom’s legs in what might be an example of insect suckling.