We’ve featured dozens of birds in the park and even more plants, but we’ve neglected the bugs. Hereby we’re making amends. In the spirit of the hugely popular Flora Friday series, this website will feature periodic Bug Day posts. Any day of the week can become Bug Day. Bugs — Arthropods — make up about 80 percent of all living species on the globe. They don’t have backbones (they’re invertebrates). Their bodies are segmented. The have a rigid exoskeleton. They’re symmetrical bilaterally. They’re hugely diverse with many millions of species. They’re easily as fascinating in the range of their powers and behaviors as any other creature. Here goes.
The European Mantis has big, powerful front legs and, when resting, seems to be praying. Hence the common name, which also percolated into the Latin name, ‘religiosa.’ An unusual religion it is, heavily matriarchal and cannibalistic. The females are bigger and heavier than the males, too heavy usually for their wings to lift them off the ground. The males are lighter and quicker and have sharper eyes. They need them to survive, because females like to attack and eat them after, during, and even before copulating. There are various theories about why this form of sexual cannibalism exists. Some speculate that the male sacrifices himself so that the female which carries his sperm will be better nourished and a more capable mother. However, males are extremely careful to avoid becoming their mate’s nutritional supplement. Already the courtship behavior shows this. In many other species, the male puts on elaborate displays to woo the female. Not the male mantis. He sneaks up behind the female and may spend hours holding perfectly still, knowing that mantises cannot see objects that don’t move. He must be super careful because mantises can turn their heads a full 180 degrees; no other insect can do that. He approaches her millimeter by millimeter until he’s close enough to leap on her back, clutch her with his powerful front legs, and start depositing his sperm. If a female bites the male’s head off during sex, he continues with the act, and may hang on even longer. Researchers, shame on them, have even removed the heads of both male and female mantises, yet the insects start and continue copulating anyway. As the season progresses, the mantis population skews more heavily female. Mantids prey on one another even absent sexual attraction, which is why hobbyists keeping mantises as pets (illegal in Germany) are advised to keep them separated. Human efforts to bring in mantises to control crop-killing grasshoppers have failed because the mantises ate one another too often to establish a viable population.
When fellow religionists are unavailable, mantises hunt other insects. Grasshoppers and crickets are among the favorites; despite their speed and jumping ability, they stand little chance against the keen vision and lightning reflexes of the mantis. But bees, flies, roaches, spiders, millipedes, snails and even worms may round out the mantis diet. Mantises only eat living prey, the livelier the better. They clasp them in their powerful forelegs and bite off the nearest portion, preferably while still wiggling.
The mantis that scientist Jutta Burger photographed, above, wears brown. Green mantises are very common. They may also be yellow and black. Much study has gone into the reasons for the color differences, but definitive answers have proved elusive. However, green mantises living in fresh grass obviously have better camouflage and are less likely to fall prey to birds; ditto for brown mantises living in dry habitats. They adopt a particular color shortly after their last moulting. But once grown, they can’t change colors to match their field, as chameleons do. The ones that venture too long outside their blending background end up rapidly snatched by predators, particularly birds.
Mantises have interesting vision and hearing. In addition to a pair of large compound eyes that face forward and allow keen perception of motion and accurate distance judgment, mantids have three “simple eyes” on the top of the head, probably useful in perceiving threats from above. When threatened on the ground, they adopt an erect posture with wings spread out to make themselves seem bigger, like humans may be advised to do when confronting mountain lions. In that posture, black and white spots on the base segment of their forelegs look like the wide-set eyes of a bigger creature. Mantises also have an ear on their belly between their hind legs. This ear can perceive a broad range of sounds from low frequency to ultrasound. The ultrasound hearing detects the echolocating pulses that bats emit.