From Ohio History Central
The praying mantis (Stagmomantis carolina; the Carolina mantis) is an odd- looking creature and a favorite of young insect collectors. Their name comes from the way the large front legs hold up the front of the body as if they are praying. These front legs are adapted to act like a pocket knife blade closing against its handle. They grab and hold on to prey with their front legs, which are serrated and spiny. In the southern United States, mantids are known as devil's rearhorses and mulekillers. Another name is camel-crickets.
The Carolina mantis is less than two inches long; other species range two to five inches long. There are approximately 1,800 species of praying mantids (the plural of mantis) in the world. Depending on the species, their coloring range from light brown to bright green. They have the ability to turn their head from side to side. Although praying mantids have wings, they prefer to sit still in bushes and low vegetation until prey is spotted. One of the most unusual characteristics of mantids cannot be seen with the naked eye. It is an "auditory Cyclops," - mantids have only one ear! The ear is tuned to ultrasonic frequencies and is used mainly to respond to the echolocation of bats.
Mantids are normally seen in late September and early October. Around this time, females are full of eggs and search for males with which to mate. Females often bite the head off the males after mating and may or may not eat him entirely. This happens between 5 - 31% of the time. Females lay a mass of eggs, an inch or so long, in a frothy, sticky substance that is glued to plant twigs or stems. A few weeks later, the female dies. The eggs, sometimes up to 1,000, do not hatch until late spring. These nymphs look like very tiny adults but without wings. They slowly develop, molting six to seven times, until they mature in August.
Mantids are true carnivores. Young mantids eat insects such as aphids and vinegar flies. They will also eat other young mantids, if necessary. As they grow, so do their choice of insects including mosquitoes, flies, and roaches. Full grown mantids can attack, kill, and eat (using chewing mouth parts) large crickets and grasshoppers. It is for their hunting abilities that they are often referred to as "preying" mantids. When doing research, it is beneficial to look under both names.
Despite their large appetite, they are harmless to humans - unless you pick one up, then be prepared for a sharp pinch from their front legs. Because most of their diet consists of insects which are considered pests to man, they are looked at as being very beneficial. Egg cases are collected, incubated and hatched and the young are sold to gardeners as a natural way of controlling harmful insects.