Sexual cannibalism: Why female praying mantis eats the male?

‘Love to death’ gets a whole new meaning when you look at mating praying mantises. Males risk their life to mate with a female. This phenomenon is also called sexual cannibalism, also seen in some species of spiders, scorpions and octopuses, and is a well-known risk when you try to breed praying mantises. When keeping mantises at home as a pet, it is a pity to lose your male in an attempt to breed with them. But why do female praying mantis eats the male? What is the benefit from it?

When females devour their mate increase the rate of survival and fecundity. A study reveals that when a female ate the male after mating has a healthier and larger clutch than females who didn’t eat their mate. However, only 13% to 28% of mating events result in the eating of the mate, and body condition and hunger are believed to be the biggest factors affecting cannibalism.

Reasons behind sexual cannibalism

It has puzzled scientist for a long time what the evolutionary benefit is of sexual cannibalism. That a male offer himself as food in the attempt to mate seems like a high price to pay; however, this phenomenon is seen by multiple species like green anacondas and some species of scorpions. So what can be the purpose of sexual cannibalism? While there are still many questions left unanswered, there are some hypotheses why sexual cannibalism happens.

  • Mistaken identity hypothesis — This was often thought to be the main reason for sexual cannibalism with praying mantises. The idea is that the mantis female can’t differentiate between sexes or even if they are from the same species or not. In other words, that the males are cannibalised by accident.
  • Adaptive foraging — If they can’t find enough food or food is needed based on the behaviour for mating and producing eggs, they could turn to sexual cannibalism. A study reveals that this is probably the main reason why praying mantis females cannibalise during the act.
  • Aggressive spillover — Unlike the adaptive foraging theory, this theory states that females are genetically inclined to be hostile towards prey and partners and that it is not happening because of the need for food.

With the praying mantis, it is believed that sexual cannibalisation is happening because of the need for food. A study in 2008 reveals that when a female eats the male during mating provides more essential amino acids that are used to lay a healthier and larger clutch. Instead of a clutch size of around 37, it increases up to 88 eggs per ootheca.

Sexual cannibalism at praying mantis
Photo by iNaturalist

Do females praying mantis always eat the males?

So, when you want to breed praying mantises, you always need to sacrifice the male? No, not exactly. While there is always a risk that the male is cannibalised during mating, only 13% to 28% of cases shows sexual cannibalism. Some species of mantises the females don’t cannibalise at all during copulation (although they can still cannibalise each other because they are hungry). These species, like ghost mantises (Phyllocrania paradoxa) and wandering violin mantises (Gongylus gongylodes), can therefore also housed in groups when kept as pets.

Other mantis species are known to cannibalise their partners more often and are therefore often labelled as “aggresive”. However, in a study in 2015 shows that males observe females closely and prefer choosing low-risk over high-risk females, in terms of probability of being eaten. Although it is not sure for every mantis species, and there is still many questions waiting for answers, it may explain why sexual cannibalism is only showing up to 28% of the mating attempts.

How to reduce the risk that a male gets devoured?

In the perspective of breeding with your own mantis pet, you don’t want to lose your male with every attempt. Fortunately, there are some ways to reduce the risk that males become mating dinner.

Preparation before placing male/female together

  • Both male and female mantis should be mature for at least 3 weeks.
  • As discussed before, make sure both female and male (but especially the female) are healthy and in good condition. Offer them as much food as possible two weeks for the mating event, so they are not hungry.
  • Plan an open introduction location with enough space so that when the time comes, the male can decide if he will approach the female or can escape when necessary.
  • Have some place for the male to hide or retreat is advised, so place a twig or artificial plant in your introduction area for the male to hide in.

Introduction of male to female

  • Always place the female first on the breeding location and feed her a large insect that takes some time for her to finish (locust or large cricket).
  • Place the male behind her on a safe distance. Make sure the male sees the female, but the female does not see the male.
  • If you notice one or both of them are stressed and not calm when transfer them don’t proceed.
  • It can take some time while slowly moving towards the female (sometimes over an hour) before the male will hop onto the female. This is the moment of truth, but if you did everything above, you have increased the chance for the male to survive its mating.
  • After correctly mounting the mating process will take some time, often one but sometimes many hours. Just leave them be and don’t disturb them. You can consider providing food to the female during the mating process. For some females, it distracts them from the male mounted on her, but for some females, it can actually trigger to attack the male instead.

When following these steps would definitely decrease the risk of sexual cannibalism towards the male.

Photo by Ned Hardy

Want to know more?

Breeding mantis is both rewarding and exciting to do, but you need to be prepared to be successful. I can highly recommend you to read the guide on the ‘basics of breeding mantises‘. It is full of more tips to increase your success in breeding with this amazing species.

New to keeping praying mantis or considering to start keeping a praying mantis? They are awesome pets to keep. I like to help you to get the best start possible, and have written a basic care guide on keeping praying mantis as a pet. Please go check it out!

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