Common Name: Praying Mantis, European mantid, Preying mantis, Religious mantis, Rear-horse, Devil’s horse, Gottesanbeterin (German), prie-Dieu (French) – The articulation of the fore-legs in what appears to be supplication forms the basis for the ‘praying’ association. The mantis or mantid surname refers to the genus Mantis.
Scientific Name: Mantis religiosa – The generic name is literally the Greek word for ‘prophet’ in the sense of an individual who speaks for a deity. This assignation was also to refer to the sanctimonious posture of the mantids. The species name reinforces the religious leitmotif.
Potpourri: Mantids are sometimes classified as orthopteroids in that they are ‘orthoptera-like;’ Orthoptera (Latin for straight-winged) is an order of insects that includes grasshoppers and crickets, in addition to the two most closely related mantid cousins, the termites and the cockroaches; as cockroaches are among the earliest insects in the evolutionary record having first appeared in the Carboniferous Period about 300 million years ago, they are the progenitors for both termites and mantids. Stephen Marshall, an entomology professor at the University of Guelph offers the observation in Insects, Their Natural History and Diversity that “much as termites are, in an evolutionary sense, social cockroaches, mantids are predatory cockroaches.” The taxonomic similarities among the three is such that they were once grouped in the superorder Dictyoptera (Latin for net-winged) but have since been separated into the cockroach order Blattodea, the termite order Isoptera and the mantid order Mantodea (Marshall provides the mnemonic IBM for this association). There are about 2,000 mantids worldwide, primarily in the tropics – only 18 are native to North America. The predominant native Carolina Mantid (Stagmomantis carolina) is not the most common, as several species have been introduced. The large Chinese Mantid (Tenodera aridifolia) was introduced in about 1895 as a beneficent insectivore and the common Praying Mantis (M. religiosa) was accidentally introduced with European nursery trees in 1899.
The Praying Mantis is the antithesis to Darwin’s “endless forms most beautiful.” It is a fearsome looking organism that deserves the sobriquet ‘preying mantis;’ they are serial killers that will eat whatever they can catch. The ancient Greeks considered them to have supernatural powers; the mantis’s fixated stare and slow undulations evidence of demonic possession. There have been a number of myths borne of this superstition: that their brown saliva can cause blindness in humans; and that a horse or mule will die if it eats a mantid (the name Devil’s horse the result). The lower body has four of the requisite six legs of the class Insecta and consists of an elongated abdomen with the sheathed wings that establishes its cockroach provenance. The upper body is another matter. The two front legs have undergone substantial evolution to achieve a raptor-like efficiency; the extension of the foreleg coxa articulates back on the upper leg femur configured with spiny protuberances to tightly grasp prey. The upper thorax, or prothorax, is extended well away from the cockroach abdomen to provide a coign of vantage for an incongruously large triangular head at its narrow apex. This seemingly fragile arrangement affords the articulation for a field of view that approaches 360 degrees, an obvious evolutionary advantage for a predator. The sinister appearance of the mantis is advanced by the large compound eyes that stand out from the head with an extraterrestrial suggestion of clairvoyance. The nightmarish and somewhat satanic appearance of the Praying Mantis lends itself to theatrical exploitation. “The Deadly Mantis” was a 1957 potboiler featuring a gargantuan mantis that was finally killed in the Manhattan Tunnel after a trail of terror and mayhem that included wiping out a NORAD base and climbing the Washington Monument.
While the mantids are harmless to humans – they don’t bite or sting – they are lethal killing machines for everything from small insects up to and including lizards, frogs, birds and even fish. Their success as hunters is due to a variety of advantageous characteristics. Perhaps the most important is visual crypsis. The outer wings, abdomen and thorax are tree trunk brown or leafy green or a combination of the two to make the mantis indistinguishable from its shrubby habitat. Thus concealed, mantids are ambush predators that rely on the chance passage of suitably sized animals for meals; they are far too slow and bulky to catch anything by chasing it down. But inside a radius of a few inches – the reach of the raptor forelegs – they are snapshot-quick. Mantid reaction time is about one half that of the common housefly – they are the only active predator that is fast enough to catch mosquitoes, flies and gnats. The necessary accuracy of the lightning strike depends on superior vision provided by the mantis’s goggle-like bulging compound eyes. Each eye contains thousands of individual ommatidia – the individual element of the compound eye that has its own cornea and one axon connected directly to the brain for vision processing – and is mounted at the outer extremes of the fully rotating head to afford pinpoint stereoscopic accuracy for the attack. So specialized are the compound eyes for predation, that the mantid also has three simple eyes mounted in a triangular configuration between the antennae for general vision and light discrimination. The combination of guile in coloration and acuity of vision is complemented by a learned behavior – mantids sway back and forth with a rhythmic movement. This may be to enhance the camouflage – swaying in emulation of the natural movement of leaves – or it may be to take advantage of parallax, noting the relative movements of prey in the oscillation. The end result is a consummate predator that must eat with regularity to provide sustenance for its relatively large bulk.
Mantids, like the other orthopteroids, do not fully metamorphose with the full four stages of egg, nymph, pupa and adult, leaving out the pupa stage in what is considered partial metamorphosis or paurometabolism. The nymph mantid is a miniature of the adult, as there is no radical change in body structure that the pupal stage engenders. The nymphs emerge in the spring in a cohort of several hundred ant-sized mantids from the protective ootheca egg mass deposited by the fertilized female the previous autumn. Their inherent voracity is immediately manifested in the assault of any small insects they can find in the immediate vicinity; regrettably, this too often includes eating each other. The cannibalism of the mantids weighs against their introduction as benign predators as their population cannot expand beyond the narrow confines of fratricide.
Since mantids do not kill outright, they normally eat their prey alive while held tightly in the clutches of their well-designed leg clamps, a gruesome reality in the fierce struggle for life that is nature. If a struggle ensues, most mantids have been observed to start with the head, decapitation an abatement to the writhing. This behavior may be more the norm than the exception, as it extends to the rather tenuous nature of the relationship between male and female mantids; females bite off the heads of males during or just after copulation, a practice euphemistically known as ‘sexual cannibalism.’ It is not known if this is an adaptive reproduction strategy or simply a manifestation of the rapacity of mantids as a family. The former is supported by the observation that the decapitated male continues to copulate, thereby increasing the likelihood of fertilization. However, a 2006 study published in The American Naturalist favored sexual conflict over sexual cannibalism in observing that males approached hungrier females with temerity, clear evidence of risk avoidance.