European Mantis

The European mantis is an ambush predator that waits motionless, relying on green or brown coloring to blend into grasses and shrubs. Its triangular head is unusually mobile, and some mantis species can rotate it nearly 180 degrees, letting the insect watch its surroundings without moving its body. Its vision is built for judging distance. Each large compound eye holds roughly 8,000 to 10,000 lenses, and a central fovea gives high resolution for spotting prey, while the edges of the eye detect movement. The eyes overlap by up to about 70 degrees in adults, giving the species stereoscopic vision. A mantis can also sway its head from side to side to help judge how far away prey is. It also has three small simple eyes.

When prey comes within reach, the European mantis shoots out its raptorial forelegs in a strike that takes only a fraction of a second. Studies of other mantis species have timed strikes at roughly 30 to 290 milliseconds, depending on the species and the prey. The foreleg is armed with spines, tooth-like bumps, and a sharp claw at the tip, which let it grasp and hold struggling prey. Mantises feed mostly on living, moving insects, including grasshoppers, crickets, cockroaches, flies, and bees. In studies of one species, mantises appeared to adjust the timing of the strike to match how fast prey was moving. This combination of patience, speed, and a firm grip helps a mantis capture agile prey.

When threatened, the European mantis stops hiding and puts on a deimatic, or startle, display. The insect spreads its wings and bends its raptorial forelegs to reveal two black eyespots with yellow or white centers at the base of the forelegs, making it look larger and more threatening. The display is largely a bluff, since mantises lack chemical defenses, but a predator that hesitates gives the mantis time to escape. Many mantises may also strike, pinch, or bite. The behavior is shown from very early life stages, which suggests an instinctive defense. Birds hunt mantises by day, and bats hunt them at night, so a ready defense matters.

European mantises live largely solitary lives. Nymphs hatch at about the same time in late spring, and if they are crowded, they will eat one another. Survivors spread out, and nymphs may even be carried away by the wind. Adult mantises also live alone. Contact between adults happens mainly for mating, and males approach females slowly from behind, freezing whenever the female moves. Females that have gone hungry for more than three days are more likely to attack a male. Although the species has been valued as a predator of pests such as spongy moth caterpillars, its cannibalism usually keeps populations too low to reduce them significantly.

Mating in the European mantis is famously risky. In a field study, sexual cannibalism occurred in about 31 percent of natural pairings, and females starved for more than three days were more likely to attack a male. Males approach slowly from behind, freezing whenever the female moves. Copulation can last four to five hours. Research on another mantis species found that females that ate their mates gained more body condition and laid heavier egg cases, which suggests the male’s body can be a useful meal. Still, more than two thirds of natural pairings in that study ended without the male being eaten. Males keep seeking mates, since reproducing is how they pass on their genes.

About 11 days after mating, the female produces an ootheca, a frothy mass that hardens into a protective case. She usually attaches it to a solid surface, such as a twig, stem, or rock, in a warm, sunny spot. A single ootheca holds roughly 100 to 200 eggs. Mating usually takes place in September or October, so the eggs spend winter inside the case, often on exposed twigs above the snow, and hatch the following spring once temperatures reach about 17°C (63°F) or higher. The female typically dies before winter, so the nymphs get no parental care. Hatching is nearly simultaneous, and newborn mantises start by catching tiny prey such as fruit flies before moving on to larger insects. Parasitoid wasps often prey on mantis eggs.