Probably the insect’s world epitome of elegant lethality is the praying mantis. There are even a couple of branches of Kung-fu based on the mantis’ movements. Increasingly over the years I have seen adults of the 3- to 4-inch European mantis (Mantis religiosa) variety in the fall. They come in two different colors, pale green and pale tan often from the same brood. This species is easy to recognize by the black bull’s eye on its upper front leg. As its common name points out, it is an import.
In the spring you can buy egg cases in local garden supply stores.
When considering them as a biocontrol in your garden you have to remember they are indiscriminate killers. They hunt whatever moves regardless whether it is good or bad for us, eating honeybees and leaf chafers with equal relish. While an egg case may hatch out 500 or more juveniles, few are likely to hang around to adulthood in your berry patch, and they are cannibalistic. Like the famous black widow spider, the females are known to eat their mates.
There is a harsh logic to it. Once the male has mated he is no longer important to his own heritage, so the nutritional value locked up in his body is the greatest thing he has left to contribute to future generations. The female does not consume the male 100 percent of the time, and researchers differ on the percentages. But they don’t just eat each other after mating. Not too long ago I happened on two mature females “doing lunch.” Damage to the victor’s wings indicates it was not a sudden ambush but a real fight. All I got to witness was the victor cleaning up the evidence.
Twice now I have seen adult mantises in the vicinity of the webs of the black and yellow Agriope spiders. This is a formidably large spider which sits in the middle of a stoutly made orb web. I assumed if there was any altercation between the two the web and the spider’s venom would give it the advantage. And twice I have returned the next day only to find the mantis still there and the web abandoned and in disarray. I can’t say for sure the mantis ate the spider in each case, but two out of two is a pretty good coincidence.
This article appears in The Pitchfork and the Mouse.
Mantis religiosa (the natural range of which extends South into North Africa, and east into temperate East Asia, including Japan, China, and Korea) is actually one of the most cannibalistic and socially intolerant of mantids.
Ootheca of M. religious generally yield 75 to 200 hatchlings, and I’ve never known very large ootheca of this species to produce much more than 300 young. Adequately nourished females routinely produce 2 or 3 oothecae (of successively declining size) before dying in the fall. The babies wriggle out more or less simultaneously and en masse through escape valves arranged in a lengthwise row in the center of their ootheca. At this stage, they resemble flattened maggots. They suspend themselves by their posterior from a silk strand that they produce during emergence, then immediately molt into miniature mantids. After their exoskeleton has sufficiently hardened via hormonal influence, they ascend and disperse, moving quickly away from their siblings. This dispersal phase generally lasts but a few hours post hatching, so if you hatch out an ootheca in a jar or other container, then keep the babies within for 24 hours, they will remain where you release them afterwards, unless food is very scarce. Baby mantis generally don’t begin feeding until a few hours or a day after hatching, so cannibalism will be rare or nonexistent if they are held this way. Adults, particularly males, will often go through a secondary dispersal phase after molting into adults and growing wings.
As every mantis breeder and researcher knows, male mantids are fully capable of servicing multiple females, or mating multiple times with the same female, without any decline in fertility. It is thus in the male’s ‘self interest’ to avoid being eaten by a female before, during, or after mating. In the Chinese Mantis (Tenodora sinensis, this is the most widespread mantis species in NA, and far and away the one most often sold in the NA mantis ootheca trade) and the Narrow Winged Mantis (Tenodora angustipennis; another introduced East Asian species that may have died out completely in NA), males rely on behavioral and pheromonal mechanisms to reduce the possibility of cannibalism by the female. In M. religiosa, males appear to be dependent on less effective pheromonal defences against cannibalism by the female. Males of any of these 3 species that make the mistake of approaching the female frontally at close range are usually seized by their thorax and eaten alive, head first. In this ‘worst case’ scenario, the loss of his brain will trigger an accelerated copulatory response from the headless male; he will crawl sideways until he is parallel to the female, then mount her and quickly initiate copulation. In more typical encounters, the male will not initiate copulation until several hours after mounting the female, and the pair will then remain in copula for 3 to 6 hours. The male will then attempt (not always successfully) to escape by leaping upwards and flying away from the female a few seconds after they separate. While cannibalism certainly occurs quite frequently among wild mantids, confinement that prevents males from flying away after mating, and keeps them in close proximity to hungry and/or unreceptive females greatly increases the incidence of such behavior.
Argiope spiders are at a huge disadvantage when targeted by a large mantis. They have very poor eyesight, and are dependent on their tactile senses for both predation and defense. Even if a mantis is hopelessly ensnared in an orb web, it can and will strike at and grasp the resident spider when the latter scrambles within range. The soft bodied spider will thus be fatally injured even if it succeeds in inflicting a bite, unlikely, since mantids instinctively ‘know’ how to grasp and subdue stinging or biting prey.
WwwWww”Tenodora” should be “Tenodera”.
Forgot to mention that a mantis entangled in a web will immediately chew through any silk strands restraining its’ forelimbs (a faster variant of the “cleaning the knives” behavior you photographed). Their extremely flexible neck (they are supposedly the only insects that can turn their heads to look over their ‘shoulders’) makes this easy. If the resident spider doesn’t attack them at this point, they will remove any silk restraining their heads by drawing this near their jaws and chewing it away, then remove any strands adhering to their compound eyes with their forelegs. Any webbing restraining their other legs and feet will be chewed away after this is accomplished.
Argiope spiders subdue large, powerful, potentially dangerous prey caught in their webs by running around close to their victim as they release multiple strands of specialized entrapment silk from their spinnerets. They use their hindmost feet to guide this silk as it is released so as to further entangle and immobilize their prey. In this, they are guided largely or entirely by web vibrations produced by the struggling insect. When the latter is largely immobilized and is thus producing less web vibrations, they will begin rotating the insect within the web as they tightly enshroud it in a wrapping of silk. A hungry Argiope will then inflict a venomous bite (the venom will assist in predigesting the meal, as most spiders are adapted to ingest mostly or only liquid nourishment), and begin feeding, otherwise it will bite the victim, then further enshroud it in silk for later consumption.
Our northern Argiope species aren’t adapted to cope with mantis predation; unsurprising, since no native NA mantis occurs within most of their range. Their spin and entangle strategy works well against bees, some wasps (spider predator wasps, such as mud daubers, have their own strategies for dealing with spider webs, and few if any attack full grown Argiope females), beetles, etc., but backfires badly with mantids, since by running around near a mantis, they move into its’ attack range. My liking for M. religiosa and Tenodera mantids notwithstanding, they are human assisted ‘invasives’ (I quite dislike the term, but it is applicable here) that may negatively impact at least some native spiders and flower flies (which are important pollinators, and often very efficient predators on aphids, mealybugs, etc. in their larval stage). These mantids also kill large numbers of native bumblebees and solitary bees, and introduced Western Honeybees.