Female praying mantises do sometimes eat their mates, but it is not the automatic ending to every mating that the legend suggests. The main driver is hunger. A male is a meal that helps a female make more eggs, which makes the act less a ritual than a feeding decision. Males are far from willing victims and go to considerable lengths to avoid being eaten.1PubMed. Complicity or conflict over sexual cannibalism? Male risk taking in the praying mantis Tenodera aridifolia sinensis Some of the most famous accounts also came from crowded, disturbed lab settings rather than from mantises left alone.
How Often Female Mantises Really Eat Their Mates
Eating a mate is called sexual cannibalism, and it can happen before, during, or after mating. How often it happens depends heavily on the female’s hunger. In Chinese mantises, well-fed females almost never ate males, with only one case recorded.2PubMed Central. Low Mate Encounter Rate Increases Male Risk Taking in a Sexually Cannibalistic Praying Mantis When males met hungry females, though, more than 1 in 5 were eaten over six hours.3PubMed Central. Low Mate Encounter Rate Increases Male Risk Taking in a Sexually Cannibalistic Praying Mantis That rate is close to estimates for wild populations of the same species.4PubMed Central. Low Mate Encounter Rate Increases Male Risk Taking in a Sexually Cannibalistic Praying Mantis It climbed to nearly 8 in 10 for males that had rarely met females and so took bigger risks.5PubMed Central. Low Mate Encounter Rate Increases Male Risk Taking in a Sexually Cannibalistic Praying Mantis Even so, in nature most matings end with the male walking away.
The legend got a boost from the lab. Many cases happen simply because a male is kept in a small enclosure with a hungry female.6Ask an Entomologist. Mantids and Cannibalism: a Surprisingly Complicated Affair Mantises are very visual animals and react to bright lights and moving observers, so early lab reports may have exaggerated how often it happens.7Wikipedia. Mantis Whether it is fully natural in the wild is still debated.8Wikipedia. Mantis In wild European mantises, the sex ratio grew more female-heavy through the season, possibly partly because of cannibalism.9Animal Behaviour. Sexual cannibalism in the praying mantid, Mantis religiosa: a field study
Hunger Is the Main Reason Females Do It
Mantises are ambush predators that seize moving insects with their spiny front legs. Females are larger than males in almost every mantis species,10Wiley Online Library / Journal of Morphology. Extrinsic and intrinsic musculature of the raptorial forelegs in Mantodea (Insecta) in the light of functionality and sexual dimorphism so a male within reach can look like just another catch to a hungry female. That fits the pattern: hungry females eat males far more often than well-fed ones.11PubMed Central. Low Mate Encounter Rate Increases Male Risk Taking in a Sexually Cannibalistic Praying Mantis In one study, cannibalized males had much lower mating success, which shows many were eaten before mating at all.12Elsevier / Animal Behaviour. The risk of sexual cannibalism and its effect on male approach and mating behaviour in a praying mantid
A female bigger than the male can overpower him and hold him with her front legs, which makes him an easy target. A male’s smaller size gives him no strength advantage, so his best defenses are timing and stealth.
Some hungry females even lure males in. Females attract males with scent signals called pheromones. In springbok mantises, males chose the scent of poorly fed females twice as often as that of well-fed ones,13Functional Ecology. Luring cannibal: Dishonest sexual signalling in the springbok mantis which suggests some underfed females advertise dishonestly to draw in males as food.14Functional Ecology. Luring cannibal: Dishonest sexual signalling in the springbok mantis Among most females, though, the scent signal matches how many eggs they can lay, and only the most starved cheat.15PubMed Central. Sexual deception in a cannibalistic mating system? Testing the Femme Fatale hypothesis
The most famous detail of the legend is the headless male. Early researchers thought biting off the head improved mating, because the movements of mating are controlled from the abdomen. That idea later looked like a lab artifact. Males can still mate briefly after losing the head, which kept the story alive, but undisturbed, well-fed Chinese mantises showed elaborate courtship instead.16Wikipedia. Mantis
What Eating the Male Does for Her Eggs
Females that ate a male improved their body condition substantially, and they went on to produce heavier egg cases than females that didn’t.17Behavioral Ecology. Female praying mantids use sexual cannibalism as a foraging strategy to increase fecundity An egg case is the foamy mass that holds the eggs. Females also laid more eggs after eating a male,18PubMed Central. Sexual cannibalism increases male material investment in offspring: quantifying terminal reproductive effort in a praying mantis because material from the male’s body ended up in her eggs and reproductive tissue.19PubMed Central. Sexual cannibalism increases male material investment in offspring: quantifying terminal reproductive effort in a praying mantis So an eaten male literally helps build his offspring, if he mated first.
Timing adds to the payoff. Late-season females must build large egg cases before cold weather, and prey can grow scarce as the season ends. A big meal at that moment matters more for egg output.
How Male Mantises Avoid Being Eaten
Chinese mantis males were less likely to approach hungrier females.20PubMed. Complicity or conflict over sexual cannibalism? Male risk taking in the praying mantis Tenodera aridifolia sinensis When they did, they moved slower, courted harder, and jumped on from farther away.21PubMed. Complicity or conflict over sexual cannibalism? Male risk taking in the praying mantis Tenodera aridifolia sinensis When forced to approach head-on, in her view, they slowed down and courted more intensely.22PubMed. Complicity or conflict over sexual cannibalism? Male risk taking in the praying mantis Tenodera aridifolia sinensis
In an Australian species, most males tried to avoid being seen at all, creeping slowly or mounting from behind.23SpringerLink. Male mating behaviour reduces the risk of sexual cannibalism in an Australian praying mantid These tactics let many males go unnoticed and greatly cut the risk.24SpringerLink. Male mating behaviour reduces the risk of sexual cannibalism in an Australian praying mantid
Approaching from behind works because a mantis strike depends on seeing movement, so a male outside her view is much less likely to be treated as prey. It also keeps him away from her spiny front legs until he has already climbed on. The trick holds only while he stays unseen, which is why he freezes or moves slowly.
Other males fight. Springbok mantis males often wrestle females before mating, each trying to grab the other first.25PubMed Central. Male coercion and female injury in a sexually cannibalistic mantis When the female wins, she always eats the male.26PubMed Central. Male coercion and female injury in a sexually cannibalistic mantis When the male grabs first, his chance of mating rises sharply.27PubMed Central. Male coercion and female injury in a sexually cannibalistic mantis Males that rarely meet females take bigger risks and are eaten more often.28PubMed Central. Low Mate Encounter Rate Increases Male Risk Taking in a Sexually Cannibalistic Praying Mantis
How to Keep a Mantis Pair Safe in Captivity
Feed the female heavily before introducing a male, because well-fed females rarely eat males.29PubMed Central. Low Mate Encounter Rate Increases Male Risk Taking in a Sexually Cannibalistic Praying Mantis Use a large enclosure so the male can approach slowly from behind. Small enclosures with hungry females produce many cannibalism cases.30Ask an Entomologist. Mantids and Cannibalism: a Surprisingly Complicated Affair Keep lights low and avoid moving around the cage during mating, since mantises react strongly to visual disturbance.31Wikipedia. Mantis
During mating, offer the female prey to hold while the male mounts. Remove the male once he dismounts, and watch from a distance rather than leaning over the cage. A female tracking the male with her head may be getting ready to strike, and a thin abdomen can be a sign she is hungry. Separate them if she lunges. Expect the female to lay an egg case days to weeks later.