Late on a balmy summer evening I saw a strange looking pair of mating mantids (or mantises—either is correct) hunting night-flying insects near the porch light. Approaching to take a closer look, I was astonished to discover a hapless, headless male closely clasping his paramour even in death. The female had bitten off his head while mating. Although this gruesome behavior, known as sexual cannibalism, is well known among mantids in captivity, it is rarer in nature where food is more abundant.
Mantids, it seems, are always hungry. Tiny young nymphs the size of an ant, emerge from an ootheca, a foamy proteinaceous egg mass that looks like beige styrofoam, and almost immediately scatter widely. In a confined space, they will turn on each other for a convenient meal. Carnivorous young mantids dine on tiny prey such as fruit flies and aphids, although some are known to first feed on pollen before switching to insects as they grow. In the garden, mantids have a reputation for eating pests; however, as generalist predators they eat whatever meal wanders by. Like most mantids, garden species are ambush hunters and can often be found hanging around flowers, a rich source of insect prey such as bees, wasps, and butterflies.
With large, wide-set eyes and a head that can rotate almost 180 degrees set on an elongated thorax, mantids have extremely good vision. While their reliance on vision for hunting means that they are largely diurnal, it is rare to see a mantis in flight during the day. Males seeking mates tend to fly at night when they are protected from birds and other predators but, like the pair that I spotted, they are sometimes attracted by lights.
Mantids possess powerful front legs armed with spines. From a still position they move these raptorial legs at lightning speed to capture and hold passing insects. This position has led to the common name of “praying,” or “preying,” mantis. Stories of tropical mantids capturing animals are often exaggerated, but large mantids are known to occasionally attack lizards, frogs, and rodents, as well as birds. If the insect prey is large and struggling, mantids begin by eating the victim’s head then leisurely complete their meal.
Mantids are in the Mantodea order, family Mantidae. Long thought to be related to Orthoptera—grasshoppers, katydids, and crickets—today mantids are known to be more closely allied to cockroaches; not surprising given that both mantids and cockroaches produce their eggs in ootheca. Like cockroaches and grasshoppers, mantids exhibit incomplete metamorphosis. Juveniles resemble wingless adults, developing wings with each succeeding stage until adulthood. In some species, adult mantids (most often females) are flightless and develop engorged abdomens. Males are much smaller and are more likely to fly.
Several garden mantids are introduced species, principally the European mantis, Mantis religiosa, the Mediterranean mantis, Iris oratoria, and Tenodera sinensis, the Chinese mantis. Egg cases purchased at nurseries are typically those of the Chinese mantis. There are a few species of native mantids in the western United States including small species found in deserts that hunt on the ground, running about rapidly in a most un-mantis like fashion. Practically speaking, it’s best to not introduce exotic species where they do not belong; it appears that established populations of Mediterranean mantises are competing with native mantids in Southern California.
The diversity of mantis species is greatest in the tropics. Tropical mantids take all sorts of bizarre forms, sometimes resembling lichen, flowers, or leaves, providing great examples of masquerade—a type of camouflage in which an animal resembles an inanimate object in the environment. This cryptic coloring provides a disguise when hunting and also protects mantids from predators. The mantids commonly found in gardens range from leafy green to twig brown. Dark markings on the underwings provide another defense mechanism. Unfurled, these markings appear to be the eyes of a larger animal to startle predators.
The science swings back and forth on whether mantids are truly beneficial insects, eating more pests than allies, or have no real impact on the garden food web. But they are a fascinating member of garden fauna and are loved by children. With their rotating heads and a small black pupil-like spot in their eyes (aptly called pseudopupils), they are a popular insect “pet” and can even become accustomed to being handled. How lucky I was that my mother appreciated the presence of mantids in our kitchen window where they would catch unsuspecting flies.