The insect order Mantodea or mantises consists of approximately 2,000 species worldwide in temperate and tropical habitats, of which a majority are in the family Mantidae. For most of the past century, only this single family was recognized within the order, and the term "mantid" was therefore historically used for any member of the order; technically, however, the term only refers to this one family, meaning the species in the other eight recently-established families are not mantids, by definition (i.e., they are empusids, or hymenopodids, etc.), and the term "mantises" (or the more colloquial "praying mantises") should be used when referring to the entire order. Often mistakenly spelled preying mantis (an eggcorn, since they are notoriously predatory), they are in fact named for the typical "prayer-like" stance. The word mantis derives from the Greek word mantis for prophet or fortune teller. In Europe, the name "praying mantis" refers to only a single species, Mantis religiosa. The closest relatives of mantises are the orders Isoptera (termites) and Blattodea (cockroaches), and these three groups together are sometimes ranked as an order rather than a superorder.
Mantises are exclusively predatory and their diet usually consists of living insects; larger species have been known to prey on small lizards, frogs, birds, snakes, and even rodents. Most mantises are ambush predators, waiting for prey to stray too near. The mantis then lashes out at remarkable speed. Some ground and bark species, however, pursue their prey rather quickly. Prey are caught and held securely with grasping, spiked forelegs ("raptorial legs"); the first thoracic segment, the prothorax, is commonly elongated and flexibly articulated, allowing for greater range of movement of the front limbs while the remainder of the body remains more or less immobile. The articulation of the head is also remarkably flexible, permitting nearly 300 degrees of movement in some species, allowing for a great range of vision (their compound eyes have a large binocular field of vision) without having to move the remainder of the body. As their hunting relies heavily on vision, they are primarily diurnal, but many species will fly at night, and can be commonly encountered at lights.
The reason for sexual cannibalism has been the subject of some debate, with some considering submissive males to be achieving a selective advantage in their ability to produce offspring. This theory is supported by a quantifiable increase in the duration of copulation among males who are cannibalized, in some cases doubling both the duration and the chance of fertilization. This is further supported in a study where males were seen to approach hungry females with more caution, and were shown to remain mounted on hungry females for a longer time, indicating that males actively avoiding cannibalism may mate with multiple females. The act of dismounting is one of the most dangerous times for males during copulation, for it is at this time that females most frequently cannibalize their mates. This increase in mounting duration was thought to indicate that males would be more prone to wait for an opportune time to dismount from a hungry female rather than from a satiated female that would be less likely to cannibalize its mate. Some consider this to be an indication that male submissiveness does not inherently increase male reproductive success, rather that more fit males are likely to approach a female with caution and escape.
The mating season in temperate countries typically begins in autumn. To mate following courtship, the male usually leaps onto the female’s back, and clasps her thorax and wing bases with his forelegs. He then arches his abdomen to deposit and store sperm in a special chamber near the tip of the female’s abdomen.
Depending on the species, the female then lays between 10 to 400 eggs. These are typically deposited in a frothy mass that is produced by glands in the abdomen. This froth then hardens, creating a protective capsule with a further protective coat, and the egg mass is called an ootheca. Depending on the species these can be attached to a flat surface, wrapped around a plant or even deposited in the ground. In spite of the versatility and durability of the eggs, they are often preyed on, especially by several species of parasitic wasps. In a few species, the mother guards the eggs.
As in related insect groups, mantises go through three stages of metamorphosis: egg, nymph, and adult (mantises are among the hemimetabolic insects). The nymph and adult insect are structurally quite similar, except that the nymph is smaller and has no wings or functional genitalia. The nymphs are also sometimes colored differently from the adult, and the early stages are often mimics of ants. A mantis nymph increases in size (often changing its diet as it does so) by replacing its outer body covering with a sturdy, flexible exoskeleton and molting when needed. This can happen up to five to ten times, depending on the species. After the final molt most species have wings, though some species are wingless or brachypterous ("short-winged"), particularly in the female sex.
In tropical species, the natural lifespan of a mantis in the wild is about 10-12 months, but some species kept in captivity have been sustained for 14 months. In colder areas, females will die during the winter (as well as any surviving males).
Generally, mantises are protected simply by virtue of concealment. When directly threatened, many mantis species stand tall and spread their forelegs, with their wings fanning out wide. The fanning of the wings evidently makes the mantis seem larger and more threatening, with some species having bright colors and patterns on their hind wings and inner surfaces of their front legs for this purpose. If harassment persists, a mantis may then strike with its forelegs and attempt to pinch or bite. As part of the threat display, some species also may produce a hissing sound by expelling air from the abdominal spiracles. When flying at night, at least some mantises are able to detect the echolocation sounds produced by bats, and when the frequency begins to increase rapidly, indicating an approaching bat, they will stop flying horizontally and begin a descending spiral toward the safety of the ground, often preceded by an aerial loop or spin.
Mantises, like stick insects, show rocking behaviour in which the insect makes rhythmic, repetitive side-to-side movements. Functions proposed for this behaviour include the enhancement of crypsis by means of the resemblance to vegetation moving in the wind. However the repetitive swaying movements may be most important in allowing the insects to discriminate objects from the background by their relative movement, a visual mechanism typical of simpler animals. Rocking movements by these generally sedentary insects may replace flying or running as a source of relative motion of objects in the visual field.
However, mantises prey on neutral and beneficial insects as well, basically eating anything they can successfully capture and devour. Although their diet primarily consists of small invertebrates, large mantises have been observed eating small vertebrates such as lizards, mice, snakes, and small birds such as hummingbirds.
Western descriptions of the biology and morphology of the mantises had become relatively accurate by the 18th century. Roesel von Rosenhof accurately illustrated and described them in the Insekten-Belustigungen (Insect Entertainments). Aldous Huxley made philosophical observations about the nature of death while two mantises mated in the sight of two characters in the novel Island (the species was Gongylus gongylodes). The naturalist Gerald Durrell's autobiography My Family and Other Animals includes an account of a very evenly matched battle between a mantis and a gecko.