Abstract

The praying mantis has long been a charismatic presence in the insect world.  Its unique look is combined with some very original and interesting aspects of behavior, that one might easily dismiss as grand.  With an estimated 1800 species of mantids that cover the whole world, the mantis has become a prevalent and often revered part of human life.  The mantis is a highly evolved insect whose name is derived from its ferocity as a predator, as well as its' virtuous stealth and sacrosanct posture.  With its excellent eyesight, patience and use of cryptic behavior, the mantis strikes with amazing speed at almost any animal its size, even small birds!.

The physiology of the praying mantis is quite unique among insects.  With a movable head, compound eyes, raptorial limbs that can regenerate when young, wings for flight, ears for hunting and evading predators, and mysterious cryptic behavior, the mantis is a highly evolved curiosity, to say the least.

Regarding its own biological imperative, the mantis has novel and infamous methods of reproduction.  The quintessential mantis femme fatale has been known to occasionally dine on the head of her mate while copulating.  Her egg laying and subsequent hatching of nymph mantids are interesting facets of behavior which warrant further investigation.

In my research paper I will focus on an overview of the praying mantids existence.  I will examine its life cycle, as well as key physiological features that help it to live, survive and reproduce.  I will focus specifically on the reproductive cycle and birth of young, the mantid anatomy in all phases of life and both sexes, its active feeding and hunting patterns, their growth and development, and their longstanding relationship with man.

By examining the praying mantis life cycle I hope to offer an informed overview of a very interesting specimen of life that has captured not only prey, but seized the collective imagination of man throughout time.

The praying mantis derives its name from the Greek language, "mantis" meaning diviner or prophet.  The name has also become interchangeable with "praying," due to its fierce predatory behavior.  To complicate matters further, the mantis is also known as the mantid, for unknown reasons.  They are also known informally as "soothsayers," "devil's horses," "mule killers," and "camel crickets" since their saliva was erroneously thought to poison farm livestock (Sargent 4).

 The praying mantis has long been a popular figure in many different cultures, and the subject of rich mythology.  In France people believed a praying mantis would point a lost child home.  In Arab and Turkish cultures a mantis was thought to point toward Mecca, a site of considerable religious interest.  In Africa they were thought to bring good luck to whomever they landed on, and could even restore life into the dead.  Here in the U.S. they were thought to blind men and kill horses.  Europeans believed they were highly reverent to god since they always seemed to be praying.  And in China, nothing cured bedwetting better than roasted mantid eggs (Sargent 4).

 Their widespread presence in human culture stems from the fact that they exist across the world everywhere but in polar climates. There are an estimated 1500-2200 different species of mantids with the common figure being 1800 species (Sargent 1).  The greatest diversity of mantids are found in tropical regions.  Africa supports some 880 species, Asia 530, Oceania 165, the Americas 410, and Europe 24 species.  In North America there are 20 species, 8 of which are in Arizona (Mantids 1).  Mantids range in size from 1 cm to 25 cm's. There are three common species in North America: European (Mantis religiosa), Chinese (Tenodera aridfolia sinesis), and Carolina (Stagmomantis Carolina).  The Chinese and European mantids were introduced in the late 1800's coming in on ships carrying nursery stock plants (Sargent 5).

 The mantis taxonomy is argued among scientists.  The debate is over what order to place mantids in.  Some place the mantis in the Dictyoptera order, which includes cockroaches.  Others believe they should be placed in the Orthoptera order, which includes crickets and grasshoppers.  The growing consensus is that they should have their own order.  For now they reside in the suborder Mantodea, and the family Mantidae.  Carolus Lineaus, founder of the scientific taxonomy, gave the species the name "Mantis religiosa" (Sargent 5).  Mantids probably evolved from the Dictyoptera order, from a cockroach-type insect.  Where roaches are largely nocturnal vegetarians, mantids have evolved into daytime carnivores, however (Patterson 3).

            There are several key characteristics that make up the mantis physiology.  Its head is triangular with large compound eyes, which help give the mantis good eyesight, but it must move its head to center its vision optimally, much like a human.  This has been an area of considerable scientific research.  Experiments have shown that a motion parallax is apparent in the mantis.  By moving its head, it measures the distance between itself and another object.  It measures an object's movement relative to its background, to gauge its distance (Kral 71).  Other experiments have shown that the mantis can only use this response if both eyes are functioning.  This dependence on binocular triangulation in relation to distance is seen as proof of stereoscopic vision, a feature only seen in vertebrates (Walcher 230).  It is able to rotate its head 180 degrees, and visually scan a total of 300 degrees.  The mantids eyes also change color depending on the light.  In bright light they appear light green or tan and in the dark they change to a dark brown (Sargent 6).

            Ears occur in 60% of mantids, and are found on the underside of the mesothorax.  The mantis is an auditory Cyclops, and having only one ear is a feature unique to the mantis, not seen anywhere else in the animal kingdom.  The ear is a deep 1 mm slit that has cuticle knobs at either end and two eardrums inside (Sargent 8).  It is located in the ventral midline between the metathoracic legs.  Interneurons in the metathoracic ganglia mediates hearing.  The ear is tuned to ultrasonic frequencies of 25-60 kHz, with thresholds of 55 to 60 decibels.  This is the range of bat's echolocation, supporting evidence that mantids, like lacewings, moths, and crickets, use hearing as a defense against predators (Yager 471).

            The neck of the mantis is elongated and very flexible, which allows it to turn and bend easily, which aids in locating and seizing prey (Sargent 6).  This neck flexibility allows the mantis head to rotate from side to side, which is almost unseen among insects (Patterson 2).

            The two front most raptorial legs are used for capturing and seizing prey.  The lower tibia of the legs has sharp spines, which aid in pinching the prey to keep it still.  These spines fold up into the femur to create a "jackknife" effect, which gives the mantis its distinctive praying position.  The upper coxa functions as a shoulder connecting the femur and the tibia to the mantids body.  If either of these limbs is lost, the mantid will die (Sargent 6).

            The four other legs are used in climbing, walking and leaping.  During the nymph molting stages, these legs can regenerate if lost, and are often replaced by slightly smaller limbs.  Adult mantids do not have the ability to regenerate limbs (Sargent 6).

            The mantis abdomen is large and segmented, and contains the digestive and reproductive organs.  It is used for sexual identification among humans.  A male mantis has eight abdominal segments, as does the female for her first developmental stages.  During female molting, two abdominal segments combine leaving her with six.  Females are also frequently larger than males and tend not to fly, especially if she is carrying eggs (Sargent 6).

            The mantid has two pairs of  wings that fold up against the abdomen when not in use.  The outermost are leathery tegmina wings that overlay and protect the inner wings, which are used for flying and startling enemies.  Flying is a response usually reserved for finding mates, and in some species the females are wingless (Mantids 1).

            The life span of a mantis is from the spring to fall seasons of one year.  Mantids begin life emerging from an "ootheca", an egg sack, when spring temperatures are sufficiently warm.  The young hatch all at once or in batches over a period of weeks (Praying 2).  The mantis nymph resembles a miniature adult without wings, and typically measure 4mm in size.  Some species emerge from the ootheca single file from an exit tube, others break from the nearest egg cell wall.  They drop from the elevated ootheca from a single silk papillae strand.  Mantis nymphs are hemitabolous, meaning they undergo partial metamorphosis from nymph to adult.  Nymphs undergo six to seven molts before adulthood, when the old skin is shed off, to be replaced by larger skin.  The process is carried out by attaching the old skin to a rough surface, often a stick, with a secreted glue-like substance.  It then chews an opening in it, creates a tear in the top of the thorax and down the back, and wriggles free of the dead skin.  Many times leg casings don't open up and many nymphs expire, unable to kick free the old skin.  Mantid nymph appetites are voracious, and they immediately begin feeding, often on each other, as soon as they drop from the ootheca.  They continue to grow until the mating season in late summer when they are adults (Sargent 9).

 The mantis has a tremendous appetite that is not limited to just insects.  They typically eat cockroach-type insects, and prefer soft-bodied insects like flies.  They have been documented eating 21 species of insects, soft shelled turtles, mice, frogs, birds, and newts (Prete 305).   One study from the excrement of an Algierian mantid showed intake of 93.2% Hymenopterous insects, and 5% arachnids (Benrakaa 253).  They are carnivorous, and only eat live prey, but have been documented in labs eating dead prey that has been manually manipulated.  They are cannibalistic in nymph and adult stages.  They are diurnal; meaning they eat during the day, but they have been spotted eating at night around artificial light sources (Sargent 8).

 The actual strike and capture behaviors have been well documented.  Original experiments have shown that the mantis responds optimally to prey (or a lure, as used in the experiments) that is 3-35 mm long and about 10 mm thick that approaches the mantis frontally rather than at right angles to the mantis.  These studies showed that the algorithms of prey recognition were similar to some other animals, like frogs, although their neural organization is dissimilar (Prete 300).  The mantid uses two primary hunting methods.  The most prevalent method, the "ambush" approach, is to wait motionless for unsuspecting prey to come within strike range.  The mantis will often slowly undulate, which is thought to mimic wind-blown foliage.  Another method of attack involves slowly stalking the prey until it gets within strike distance.  When it does attack, it does so at speeds so fast humans can't perceive it.  The strike takes a mere 30-50 one-thousandth of a second.  The mantis impales its prey in the spines between the lower tibia and upper femur of its front raptorial limbs.  This action is followed by immediately incapacitating the prey by chewing on its neck.  They are capable of holding prey in one forelimb and striking out at another, and sequentially eating them both.  If the mantis is well fed, it will selectively eat only the choice parts of an insect.  If it happens to drop any part while eating, it will remain discarded (Sargent 8).

 The mantis has novel defense mechanisms.  Its common natural enemies include birds, mammals (mostly bats), spiders, snakes, and humans, since the mantis has no defense against pesticides.  They rely primarily on camouflage and cryptic behavior, stealth, aggressive displays, and auditory related flying evasion as defense mechanisms (Sargent 10).

 Camouflage is a response that varies in different species of mantids.  Adult mantids are typically green or brown, but come in a wide variety of colors and flavors.

Recent research has shown that European mantids adapt their color to the environment.  During the nymph molting stages, wet environments will produce a green colored mantid, and dry environments tend to produce brown colored mantids (Teyssier 1).  Some species combine camouflage with mimicry.  An interesting example is the Burmese mantid, which has a petal-like protothorax that is lavender and pink, resembling a prominent local flower.  It so closely mimics these flowers that it displays positive phototrosis, pointing itself toward the sun (Portman 63).  Other species mimics leaves, twigs, and grass.  In one species, the nymph mantis mimics small ants (Mantids 1).  Some species mimic much larger animals, by displaying conspicuous eyespots on wings and beneath the forelimbs, when startled (Portman 63).  This startle display is another defense mechanism triggered when the mantis senses danger.  It rears onto its hind legs and rattles its wings to create a hissing noise designed to intimidate (Sargent 10).  The mantis relies on its ability to remain still for long periods of time as a defense mechanism as well.  By blending into its surroundings and not moving, it is easily overlooked by other predators (Sargent 10).

 The mantids ultrasonic detecting ear is a main tool of defense.  The ear is tuned to the 25-60 kHz range, which is the frequency used by bats for echolocation.  The mantid uses its ability to hear primarily when in flight.  When it hears a bats signal, it curls its abdomen up and thrusts out its raptorial forelimbs, creating an aerial drag and stall, sending the mantis spiraling earthbound (Alcock 143).  Recent experiments show a correlation between the volume of a heard signal and mantis flight pattern.  The louder the bats echolocation signal, the more erratic the mantid flight pattern (Abrams 2).

 The mantids reproductive processes are a heavily studied area.  Reproduction occurs during the late summer season.  The female secretes a pheromone to attract males.  Three distinct patterns of courtship have been observed.  The most common method is when the male mantis approaches the female frontally, slowing its speed down as it nears.  The second most common approach is when the male approaches the female from behind, speeding up as it nears.  The most seldom seen method involves the male remaining passive until approached by the female (Liske 1525).  Much has been made of the cannibalistic response in the mantis while copulating.  In actuality this only occurs 5-31% of the time.  This occurs most often because the female is hungry and a mate's head provides an instant source of energy for her.  In one species, however, it is necessary that the head is removed for the mating to take effect properly (Praying 2).  Experiments have been done to show that under certain food intake situations it is in the mantids best interest to reduce the competition for food, but as the male mantid tries to escape, it is probably only in the females best interest (Birkhead 112).   The actual mating response process has been described as initial visual fixation on the female, oscillation of the antennae, a slow and deliberate approach, abdominal flex displays, a flying leap on the back of the female, mounting, antennae lashing by the female, rhythmic S-bending of the abdomen, and intromission (Liske 1526).

 The males package their sperm into a spermataphore and place it into the female spermatheca.  In one experiment, mantids were observed in copulation for an average of 6 hours.  The males flew away directly after mating (Terra 3).  As the female eggs pass through her reproductive system, the stored sperm fertilizes them.  After finding a raised location (branches, stems, building overhangs, etc) special appendages at the base of the female abdomen froth the gelatinous egg material into an ootheca shape that differs among species.  It exits through the female ovipositor, as she instinctively twists her abdomen in a spiral motion, which creates individual cells within the ootheca.  These cells provide insulation against the cold winter temperatures to come.  Egg laying takes between three to five hours and can occur as little as one day after mating.  The ootheca then hardens into a paper mache type substance that prevents predators from eating them (Sargent 11).  The amount of eggs laid varies among species, but it is usually between 30 and 300 eggs per ootheca.  A female mantis is capable of laying up to 22 ootheca, depending on food intake (Praying 3).  After laying their eggs, the mantis has typically two weeks of life left (Lyon 3).

 The mantis remains a source of curiosity to the novice enthusiast and professional entomologist alike.  A brief examination of its history and life cycle shows that the behavior and physiology of the praying mantis are compelling the closer one looks.

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