At a length of about 11 cm, this immense insect is an adult specimen of Tenodera sinensis (Mantodea: Mantidae), the Chinese mantis. (The former scientific name of the species was Tenodera aridifolia sinensis, which many people still use.) I found the depicted specimen in the garden outside my office building yesterday. Indigenous to temperate parts of East Asia, the Chinese mantis was introduced to the eastern United States probably during the 1890s, and the species now thrives in many parts of this region. Like other mantids, Tenodera sinensis is a consummate ambush predator that uses plant-like camouflage, utter stillness, acute eyesight, and swift raptorial forelegs to capture prey on vegetation near the ground.
In brushy undergrowth, the leaf and stalk mimicry of Tenodera sinensis makes it essentially invisible to most animals while it is motionlessly awaiting the approach of prey.
The life cycle of Tenodera sinensis lasts about one year. In North America, the females typically reproduce just once. Breeding occurs in the late summer and early autumn. After gravid females produce their eggs, they die in the first frosts. The eggs overwinter, and the young hatch simultaneously when the weather becomes warm enough in the spring. Growth and development toward maturity proceed during the late spring and the summer. Along with the general dangers faced by insects, cannibalism is rife among the young of Tenodera sinensis, and it has been estimated that only a tenth of an annual generation survives to reach sexual maturity, which is attained by the late summer.
The cannibalism does not always stop with adulthood. Females often kill males during mating, and a female will sometimes eat the male if she needs the nourishment to complete the development of her eggs. Under the selective pressure of female sexual cannibalism, males have evidently evolved to make the best of a fatal encounter with a female: decapitation during mating may actually enhance the male's copulatory efficacy. While males do not really gain an overall reproductive advantage by being killed during copulation, as survivors can pass on their genes with several females, the heightened copulatory performance that follows sexual cannibalism seems to be a kind of evolved contingency plan.
Although superficially different, mantids (the order Mantodea) are close relations of the cockroaches (Blattodea), and some taxonomists consider them to be suborders within a single overarching order (Dictyoptera). Indeed, mantids are essentially big predatory roaches that have evolved a variety of forms to camouflage them as they wait to snatch passing prey.
In a clear indication of the close evolutionary link between them, mantids and cockroaches are the only two groups of insects that produce an egg case, called the ootheca. The noun is a compound of oo- (a combining form of Greek ᾠόν "ovum, egg") + theca (Latin for Greek θήκη "case, cover"). After a female mantid or roach has been fertilized, the ootheca containing the eggs extends from the rear of her abdomen. She carries it around before depositing it in a suitable place. The ootheca prevents the desiccation of its enclosed eggs and, in fact, keeps them so well hydrated that often no external moisture is needed for egg survival and development.