Praying mantis is the common name for any insect in the order Dictyoptera, suborder Mantodea. All of these insects are predators. The most important family in this group is Mantidae; hence, the general name for these insects often is given as “mantid”, rather than “mantis.” Mantids are closely related to cockroaches, termites, and grasshoppers. Approximately 1,800 species have been identified worldwide, most of which are tropical. The most common native species in the United States is the Carolina mantid, Stagmomantis carolina, which is found from New Jersey to the Gulf Coast in the eastern half of the United States. The most abundant and widespread species, the Chinese mantid, Tenodera aridifolia sinensis, was introduced from Asia at the end of the nineteenth century and can be found from South Carolina to Long Island east of the Mississippi, as well as in portions of the Midwest andWest Coast. Another well-known imported species is Mantis religiosa, the distribution of which is limited to northern states and Canada because its eggs require cold winters before they will develop and hatch in the spring.
Mantid Physiology
The praying mantis has the most highly mobile head of any insect, attached to the front of an elongated prothorax (foremost midbody segment), and spiny front legs also attached to the prothorax. These specialized forelegs are folded when the animal waits motionless in ambush for its prey, giving it an attitude of prayer (hence, the common name for the group). Although most mantids are sit-and-wait ambush predators, some species actively hunt and chase their prey over short distances. The sensory systems of mantids have been well studied. Mantids can integrate detailed information from their environments, and have exhibited a highly sophisticated array of responses to external stimuli, such as light, chemicals, and sound. They are able to use binocular vision to accurately estimate the striking distance to their prey, or the distance between perching sites in vegetation. Female mantids produce sex pheromones to attract males during mating season. Some species can hear ultrasound emitted by bats, and thus avoid predation when they fly at night. Sexual behavior and cannibalism in mantids has been the subject of much folklore and scientific speculation. Females of many species sometimes eat males before, after, or even during copulation. The outcome of male-female encounters is mainly a function of hunger level in females, and males often escape to mate with other females later on. The reputedly suicidal behavior of males is not really a sacrifice, because a male cannot tell in advance the hunger state of his prospective mate, or whether her eggs have already been fertilized by an earlier encounter with another male.
Mantid Life Cycle
Mantids inhabiting temperate geographic zones generally live from spring to autumn, and the adults all die with the onset of cold weather, leaving the eggs to winter over. Development of mantids is hemimetabolous: Eggs hatch out into nymphs that are miniatures of the adults, except without wings. Nymphs grow through as many as seven stages (depending on species), increasing body length tenfold before developing wings as adults near the end of the season. The largest species in the United States, Tenodera aridifolia sinensis, maygrowas large as ten centimeters (four inches), and often appears even larger to startled human observers. Very few hatchling nymphs survive the growing season to reach adulthood, most of them dying of starvation and the rest from predators such as spiders. Adults are large enough to escape predation by most other invertebrates, but vertebrate predators such as birds and lizards actively prey on them. Cannibalism between same-sized mantids is relatively rare except under crowded conditions in captivity where they cannot avoid one another, but larger nymphs will readily eat smaller ones. The variable feeding opportunities in natural ecosystems cause variable growth rates among nymphs within a season, so cannibalism among different-sized individuals may be common in nature. Praying mantids simultaneously occupy two trophic levels, feeding on both herbivorous and carnivorous arthropods. This makes their use in pest control problematic: If they eat grasshoppers they may be beneficial, but if they eat spiders they may be harmful. There is evidence that mantids can enhance plant growth by eating herbivorous insects, but their impact is likely to vary depending on the plants and other arthropod species present.
