Friday, Oct. 25, 2002
* Japanese name: Himekamakirimodoki
* Scientific name: Mantispa japonica
* Description: Mantidflies are about 25 mm long. They belong to an unusual order of insects, the Neuroptera (the name means "network wing"). Like other neuropterans, such as lacewings, mantidflies have two pairs of fine, delicately veined wings, equal in size. They also have an elongated body and prothorax (a "neck"). However, the forelegs of mantidflies are long, strong and sharp, modified to catch prey. The forelegs (and the triangular head) are characteristic of another insect, the praying mantis.
* Where to find them: In woodlands and grasslands from Honshu to Kyushu, June to October. Adults are attracted to ultraviolet ("black") light and can also be found by dragging a sweep net through vegetation. Mantidflies lay clusters of up to 1,000 eggs on leaves. Eggs hatch in 11 to 30 days.
* Food: Mantidflies have chewing mouthparts. The larvae are parasitic, inhabiting the egg sacs of ground spiders and wolf spiders. They feed on the spider's eggs, and when fully grown, the larvae spin cocoons and pupate. Larvae may also prey on the larvae of wasps and bees, sometimes depleting hives. Adults are diurnal (active during the daytime). They alight on flowers of thistle and other plants, preying on plant-feeding insects (aphids, lady bugs, stink bugs). According to some reports, mantidflies are cannibalistic.
* Special features: The prominent raptorial forelegs of mantidflies would seem to suggest that they are related to mantids, but the praying mantis, in fact, belongs to an entirely different insect order (the Mantodea). Cats and horses, for instance, are in different mammalian orders, so it's clear that mantidflies and praying mantises must be very different from each other because they don't belong to the same insect order.
Then why are they so similar? Both insects are sit-and-wait predators, staying still for long periods until another insect chances to come close. Then they lash out with their powerful forelegs. Both mantidflies and praying mantises have independently hit upon the same solution to their dietary needs -- using their raptorial front legs. Biologists call this "convergent evolution." It's the reason that both fish and dolphins are streamlined and have fins, despite being unrelated.