A small regular rocking motion in the hydrangea bush beside my deck-chair caught my eye as I relaxed with a book in the garden.
Though it was less than half a metre from my head, up to that moment I had been unaware of a foreign presence, so seamlessly did the creature’s colour merge with the leaves.
Against an unchanging background, it is often motion or disturbance that catches our attention, and the praying mantis on the hydrangea leaf had been similarly alerted.
A blowfly had landed a few centimetres in front of it, and was now raising first one hindleg and then the other to rub against the sides of its hairy abdomen as flies do when grooming themselves.
The fly was not directly in front of the mantid but off to one side, and the mantid had turned its head to look directly at it.
It is an uncanny head, strangely robotic and extraordinarily mobile; a triangle with an eye at two corners and a set of jaws at the third. In some lights, the bulbous compound eyes set wide apart to give maximum binocular vision are translucent and seem hypnotically deep, with just a pinprick of brown at the bottom. In a way that no other insect can, when a mantid looks at you, you feel looked at. Checked out. Sized up.
The mantid’s stance conveyed intense concentration and readiness as it checked that the fly really was a live animal within striking distance, and not just a piece of plant debris or a bird dropping that had fallen from above.
It stopped rocking and the fly stopped grooming, and for a tense moment I wondered if the fly was aware of its peril. It appeared to be just out of striking range. Ten seconds passed with no movement from either party.
Suddenly, the fly took a few steps forward, and out flashed a pair of arms bristling with pointed daggers.
It was all over in the blink of an eye. The hands that had a moment earlier been held together in supplicant prayer like position perhaps saying grace were now holding lunch to lip. There was no further ceremony, just a mechanical munching of insect skeleton and tissue.
For a few moments the fly attempted to struggle free, but with both wings and four of its legs clamped to its body by the mantid’s toothed arms, resistance was futile. In short order the head was consumed, and the mantis was chewing steadily through the muscular thorax. Five minutes later, the repast was over and all that remained of the fly were the wings and the ends of two legs, lying on the leaf.
Immediately, the mantis began cleaning its forelegs, working carefully between the spines to remove all traces of the fly flesh and fluid that had oozed out of puncture wounds nutrients that could possibly give bacteria a foothold. Mantids are fastidious about personal hygiene. After washing their limbs with saliva, their complex mouth parts are cleaned much as we brush our teeth after a meal. The toothbrushes are small pads of soft flattened bristles, known as femoral brushes, on the insides of the forelegs. These brushes are equally important as windscreen wipers. Maintaining clear vision is vital to a predator, and the mantis frequently wipes the pads gently across its eyes to keep them perfectly clean.
On completing its toilet, my mantis reassumed the praying stance perhaps giving thanks and, immobile as stone, awaited the next victim.
The specimen I had been watching was the winged adult of the New Zealand praying mantis, Orthodera novaezealandiae. Over the years, there has been uncertainty whether it is the same as an Australian species 0. ministralis, and although the two species are closely related, at present the local one is thought to be distinct. In Australia there are over a hundred mantis species, but in New Zealand (until nearly 20 years ago), the mantid family had only a single representative.
In 1978 a second species, Miomantis caffra, of South African origin, suddenly appeared in Auckland gardens. It spread quickly through the north, and more slowly south, and is now found locally throughout the North Island and the north of the South Island. It seems to be displacing the native species, at least in some urban areas.
Given the close relationship between 0. novaezealandiae and its Australian counterpart, it has been suggested that 0. novaezealandiae itself was introduced from eastern Australia to New Zealand in the mid-1800s, perhaps with animal fodder. During the 1870s and ’80s it became common in numerous locations where it had not been noticed previously. Whether pre-European Maori were familiar with the species is uncertain.
Other mantids entering the country as illegal immigrants on imported goods have been intercepted from time to time by Ministry of Agriculture and Fisheries officers, but most members mantises are tropical and subtropical insects that would not survive here. The two species that do thrive are at the southern limits of worldwide mantid distribution.
Some tropical species are extraordinary creatures over 12 cm long, with frills, spines and coloration to camouflage them perfectly amongst particular plants or dried leaves. Some mimic other insects, instilling a false security in the mimicked specimens that frequently presages their deaths.
The New Zealand mantis is almost uniformly leaf-green, though some specimens have fine reddish-brown highlights on the head and along the edges of the forewings. On the inside of each femur is a conspicuous colour patch, like a large “eye-spot” coloured indigo at the centre, grading to lighter blues and turquoise at the edge. These are not (as is sometimes claimed) the mantid’s ears, though the insects do have a small hearing organ, the cyclopean ear, on the underside of the thorax. Males grow to about 40mm in length and are more slender-bodied than females, which are up to 5 mm longer. The species occurs from North Cape to Bluff, but is absent from the high country and rare on the South Island’s wet West Coast.
The South African mantis is a slightly slimmer bodied species which can grow a little longer, with some females reaching 50 mm. They are commonly a paler, bluish-green colour, but are more variable, and some individuals are plain beige or khaki. They never have the “eyespot” on the foreleg, and males frequently have pinkish highlights along the narrower thoracic shield (neck), and on the slender wings and upper joints of the legs.
Mature females of the two species are easily distinguished because the abdomen of the New Zealand mantis is evenly swollen along its length and almost completely covered by the wings, while the abdomen of the South African mantis is plumper posteriorly like a club, and protrudes out well beyond the wings, which are rather short. The South African adult female is incapable of flight (despite her wings), but females of the local species can fly, though not strongly. Both can spring a surprising distance, despite lacking the muscular hindlegs of, say, a grasshopper.
Mantids respected for their ability to catch and kill are closely related to that much-reviled scavenger, the cockroach. In contrast to the scuttling cockroach, the praying mantis stands upright, with head held high, boldly surveying all about. It is the only insect that will turn its head to look you in the eye.
Never scurrying, it moves deliberately with a measured tread with what used to be termed deportment or carriage and amongst insects it has a warrior’s demeanour that others do well to heed. Poised ready to strike, it is altogether the lion rampant of the insect world.
That mankind has respected this proud persona is shown by numerous depictions of mantids through the ages. Certain Greek coins were impressed with a praying mantis beside an ear of corn perhaps signifying that possession of money assured the holder of both food and power. In China, the mantid’s stance and its speed and style of offence inspired a style of kung fu, the martial art of unarmed combat which uses attack as a form of defence. Developed by the renowned exponent Wang Lang in Shantung Province 400 years ago, this style mimics many of the postures and movements of the mantis.
In artwork, the mantis is also a frequent subject, and often one of commentary. It has been depicted in everything from African cave paintings to Escher’s enigmatic drawings, one of which depicts a mantis standing on the chest of a mitred cleric, laid out to rest in a stylised chapel, apparently administering last rites.
High human regard for the praying mantis is reflected in its use as a food in Thailand and a medicine in China, in accord with the Asian belief that the respected qualities of other animals, especially predators, can be acquired by consuming those animals, or suitable extracts from them. In South Africa, the admiration has become ritualised tribal worship of mantids, while in Japan they are used in sporting contests accompanied by heavy gambling. More pragmatically, in New Zealand and the United States the mantis is being increasingly fostered in gardens as a natural method of pest control.
Most Insects use all six of their legs for walking, but the mantis is unusual in that it typically stands and walks on just four the middle and hind pairs leaving the forelegs ready for aggressive action. On occasions, though, it does use the curved talons on the end of its front tibia as grappling hooks to aid climbing.
Just a glance suffices to reveal that there is something abnormal about these Z-shaped forelegs, and, indeed, they are highly modified for their raptorial function. The basic insect leg has five segments: coxa, trochanter, femur, tibia and a tarsus that is usually multi-jointed. Typically, the femur and tibia are the main members of each leg, and the coxa and trochanter are just short articulation sections close to the body that allow the leg greater movement about its point of attachment.
(This arrangement allows a fly, for example, to turn its hind legs up over its back when grooming its wings.)
The mantid’s foreleg has a greatly elongated coxa the same length as the long femur. In the praying position, the forelegs are tucked neatly away beneath the chin, but when fully extended they can reach forward a distance equal to nearly three-quarters of the body length.
This reach is further extended by the positions of the legs on the unusually long mantid thorax. The forelegs arise at the front, just behind the head, while the mid- and hindlegs attach just in front of the abdomen.
The mantis often stands with its thorax raised and head held high, as noted in a Japanese haiku: Praying mantis With his head in the air, Like a child learning to walk.
By lowering the chest very slowly so as not to attract notice, or by dropping it quickly as it lunges, the forelegs are also brought closer to the quarry, and a further extension can be achieved by straightening the hind legs to thrust the whole body forwards. A pair of small claws at the end of the flexible tarsal fingers and a menacing talon extending out of the end of each tibia equip the flashing weapons perfectly for snaring any prey within reach.
As the folding legs draw the prey back towards the mouth it is crushed and skewered between the double row of spines along the rear edge of each femur and the single opposing row along the tibia. Though the victim may struggle, there is rarely any escape, and the predator, not waiting for death, starts chewing straight away at the part of the prey that happens to be closest to the mouth, be it head or abdomen. Nothing digestible is wasted.
It appears, though, that a clean capture is critical, for the mantid must avoid being stung or injured by prey desperately struggling to escape. Small mantids eat small prey, such as white flies, vinegar flies and the winged dispersal stages of aphids, but mature mantids do not bother with these morsels. They prefer larger meals, and at each nymphal stage there must be a maximum size of prey that can be tackled safely.
Adults of both mantids can secure a German wasp, a honeybee or large specimen of the common brown blowfly. However, insects of this size are at the mantids’ limit, for if the strike is not completely successful the mantis does not bother with a better grip, but rather releases the potential problem as quickly as possible with much flicking of the arms. Occasionally, young mantids do lose a leg when tackling oversized prey, or perhaps when pecked at by a bird, but they are able to regenerate a replacement which, over several moults, reaches near normal size.
Praying mantises are generally regarded as opportunistic predators, rather than active hunters. They lie in wait, camouflaged to look like the surrounding vegetation, and poised to snatch up any hapless insect or spider that, by chance, wanders too close. While this is generally true of adults, juveniles are often more active. They scamper half a metre or so before freezing for a few minutes on the chance that potential prey may show itself by moving, but if unsuccessful then run on again.
So voracious are mantids that occasionally one can be observed to catch a second fly before the first is finished. A large female was once observed to devour 26 house flies in a three-hour period.
Mantids do not restrict themselves to insects of other species. In fact, in no other animal is the expression “You are what you eat” more apposite. When the food supply is insufficient to satisfy the demands of the many juveniles that hatch out in the spring, some of them sup on their siblings. Older nymphal stages appear to be less susceptible to being eaten perhaps by avoiding each other but close contact is in escapable for adults when mating.
The praying mantis is such a compulsive killer that attempting to mate with a female can be a life threatening exercise for the males. Suitors must approach slowly, and in such a manner that they are properly recognised. They probably also need to sense whether the females are receptive to an amorous encounter. Even when a female does signify her willingness, any male that responds could be said to have fallen for the original fatal attraction, because males of many mantis species are devoured by the female immediately after a successful mating.
After establishing its credentials a male must very carefully mount the female from behind in such a position that it can twist the end of its abdomen around to engage it with the female’s genital aperture. The New Zealand mantis appears able to
John walsby is a frequent contributor to these pages. His previous subjects have included glow-worms, crabs, mangroves and paper wasps. achieve this by curling its abdomen over the tip of the female’s while keeping its body closely pressed against her back, where it is out of reach of those murderous forelegs. After mating, the males are normally able to retire without loss of limb or life.
The male South African mantis, meanwhile, stands up on the female’s back in order that his and the female’s genitalia can be opposed. This appears to be a more hazardous procedure, for it results in the males standing slightly to one side of the female, and invariably they are consumed by their femme fatale immediately after mating, or even while coitus is still in progress.
The nineteenth century French entomologist J. Henri Fabre claimed that a single female mantis could mate with and devour up to seven males in succession. Elaborating on these bizarre rites, the American author Annie Dillard writes (in Pilgrim at Tinker Creek): “A chemical produced in the head of the male insect says, in effect, ‘No, don’t go near her, you fool, she’ll eat you alive.’ At the same time a chemical in his abdomen says, ‘Yes, by all means, now and forever yes.’
“While the male is making up what passes for his mind, the female tips the balance in her favour by eating his head. He mounts her. Fabre describes the mating, which sometimes lasts six hours, as follows: ‘The male, absorbed in the performance of his vital functions, holds the female in a tight embrace. But the wretch has no head; he has no neck; he has hardly a body. The other, with her muzzle turned over her shoulder, continues very placidly to gnaw what remains of the gentle swain. And, all the time, that masculine stump, holding on firmly, goes on with the business! . . . I have seen it done with my own eyes and have not yet recovered from my astonishment.”‘
Hardened observers might reason that, having completed fertilisation, the male’s role in life is accomplished, and his most worthwhile contribution is to have his body reprocessed through the female into eggs from which the next generation will emerge. The truly sacrificial mate.
Eggs are laid in batches in a foamy case called an ootheca. Oothecae laid by South African females are greenybeige as they are being laid, drying to a creamier colour, and look like small meringues. They are generally laid in sites that offer some protection—on or under buildings, amongst stacked wood, between the slats of transport pallets and even under the wheel arches of vehicles. (It is probably through the movement of goods and vehicles that this mantis was first brought to Auckland in oothecae, and subsequently spread to different regions of the country.)
The New Zealand mantid’s cases are smaller, more slender and brown in colour. They are constructed by the female moving her abdomen from side to side to lay down a continuous ribbon, gathered like a series of figures-of-eight and enclosing two staggered rows of egg chambers. Foam produced at the same time sets to form the strong outer case.
Shelter is seemingly not important for the native mantid’s cases, for they are commonly found attached to exposed faces of branches, fence posts and other hard surfaces out in the open. An ootheca of the native mantis usually has about 20 chambers, each containing several eggs. From a total of about 50 eggs, two or three dozen nymphs emerge.
As well-fed females lay a number of oothecae during summer and autumn, each mantis is capable of producing over a hundred juveniles which will appear in the following spring after overwintering in their tough weatherproof nurseries. The five or six months spent in the egg cases is long compared with most tropical species, which emerge in just a few weeks. Nymphs go through six instars, and the first adults appear about mid-February. Very few adults of the native species seem to survive beyond June.
Oothecae of the South African mantis usually contain more chambers than those of the local species, often up to 50, in each of which there is an average of four eggs. Over a hundred nymphs may hatch, but determining the exact number is difficult. Although many of the nymphs within a single ootheca emerge over a few days, development appears to be staggered, often over several weeks or months. From one carefully observed ootheca, a few nymphs hatched 12 months after the first had appeared, indicating that the oothecae also serve as long-term dormancy shelters, assuring species continuity against a local natural disaster in any one year.
This staggered hatching contrasts with the synchronised emergence of New Zealand mantid nymphs. In the native species, all within an individual ootheca emerge within a couple of days. Higher temperatures trigger hatching, and the particular location of each ootheca is therefore likely to affect its hatching date.
The difference in the annual cycle between the species may be implicated in what appears to be a gradual displacement of the native mantid by the introduced South African species. With the latter producing more juveniles and having larger nymphal stages, and even some overwintering adults present in the spring, the newly hatched native juveniles face greater competition for food, and may also become prey for the introduced mantis.
Auckland entomologist Trevor Crosby considers that another relatively recent insect arrival the Asian paper wasp (see New Zealand Geographic, Issue 26) could also be con‑
tributing to the decline of the native mantis. “Our local species always sits on the tops of leaves, where it is easily seen and picked off by prowling wasps. The South African species prefers to live underneath leaves or in long grass, where it is much less conspicuous.”
There is an element of mystery about the sudden appearance of nymphs from the top of an ootheca. In addition to the seasonal temperature change that is thought to signal to the individuals tucked up inside that the harsh conditions of winter are past and the warmth of summer is approaching, there must be some communication between the infants within the protective nursery to stimulate so many to emerge at the same time.
Suddenly, the caps at the tops of the chambers are forced open, and out pop the heads and upper bodies of baby mantises. These pronymphs emerge like babies wrapped in swaddling clothes, with their slender legs seemingly bound to their bodies, and they rest for a while like pieces of toast poking out of the top of a pop-up toaster. Presumably, they must wriggle out of their cribs like a mountaineer “chimneying” up a narrow crevice, and then rest to build up strength to break out of the sheath that trusses the legs to the body.
Only occasionally do other insects prey on the praying mantis. Several species of small wasp parasitise the oothecae of New Zealand mantis. So instead of young nymphs hatching, wasps emerge. Adult mantids have at times been killed by eggs or larvae of the fly Sarcophaga crassipalpis which, after being swallowed whole, have survived and continued to develop within, ultimately to eat their way out. presumably lays her eggs in freshly constructed oothecae while the frothy matrix of the walls and capsule caps is still soft and easily penetrated by the wasp’s ovipositor.
Inside our home , the prevailing convention seems to be that the only good insect is a dead insect. Phobias notwithstanding, mantids are agreeable creatures to have as free-ranging pets inside the house, where they provide great interest and act both as natural fly killers and controllers of aphids and other insect pests on indoor plants. In India, mantises were traditionally kept tethered by one of the hind legs with the finest of gold chain, especially as companions for sick persons confined to bed.
Catching them is not difficult, for they will normally oblige by just walking on to a finger placed directly in front of them, and stand placidly there while you carry them indoors for release on a pot plant.
Watching newly hatched nymphs emerge from their ootheca, and raising them on small flies is as fascinating as keeping adults as house guests. An ootheca affixed to a dead twig can be brought inside on that stick and placed in a large jar or small aquarium with a loose-fitting lid that will constrain the mantids but allow air circulation. Placing the container in a prominent position reminds you to inspect it every day, so that you do not miss the sudden emergence of the juveniles.
The young mantids require a steady supply of very small flies, and this is most easily provided by starting a culture of vinegar flies in a small bottle. Mash a heaped tablespoon of brown bread with twice the volume of overripe fruit such as tomato or peach, and add just enough water to make it into a smooth paste inside the bottle. Placed with the top open beside the fruit bowl or outside by the compost heap, and the culture will, within a day or two, be colonised by the vinegar fly Drosophila.
From eggs laid in the culture me dium, fly larvae mature quickly and soon pupate on the inside of the bottle, emerging as adults after about a week. By placing the open culture bottle inside the baby mantids’ terrarium, a reliable source of suitable living food is provided as the vinegar flies fly in and out to feed on the moist fruity broth, and lay their eggs in it to produce future supplies of mantis food.