For the explanation of this phenomenon, biology has a proper noun explanation-"sexual cannibalism". Before, after or during the mating of these animals, females will eat the males they mate with. This phenomenon is common in spiders, mantises, sea slugs and other species.
So far, scientists have explained the phenomenon of sexual cannibalism with hunger theory.
Hunger theory
1984, scientists conducted a scientific experiment on sexual cannibalism. Scientists Scott and Davis believe that the female mantis ate the male mantis because of hunger.
To test their conjecture, they did a simple experiment: after all the female mantis were fed, they mated with the male mantis. It was found that during the whole mating process, no female mantis ate her mating object.
But this experiment is not a complete scientific experiment, because a more rigorous scientific experiment needs to set up an observation group besides the experimental group, and the number of these two groups should be enough to accumulate enough data and avoid errors. There is only one experimental group in this experiment, which is obviously unconvincing.
However, Riske and Davis conducted a second experiment, and they set up three groups.
The first group is a mother mantis that has been hungry for many days. The results showed that this group of female mantises chose to eat the same kind almost before mating, so that they didn't mate in the end. The second group is a half-full female mantis. The results show that the female mantis has been trying to eat the male mantis during or after mating, but most of the male mantis has escaped. The third group is a plump female mantis. The results show that they are not interested in the male mantis and will let it go after mating.
It can be seen that the most fundamental reason why nature selectively eats the same kind is hunger.
As for the suggestion that the female mantis eats the same kind in order to make the male mantis secrete more sperm, this can't stand scrutiny, because the hungry female mantis will eat the male mantis before mating, so that the male mantis can not secrete sperm to mate with it.
There is also a hypothesis that protein of male mantis can provide more nutrition for female mantis, thus ensuring that female mantis can get pregnant better. Others understand this behavior as "dedication of love". In fact, this statement can't stand scrutiny, because it's not that male mantis is willing to be eaten by female mantis, but that they can't escape before being preyed by female mantis. And generally speaking, the female mantis doesn't choose to eat the male mantis immediately after preying on its prey.
Why doesn't the male mantis run?
In 2008, a research paper was published in the American journal Naturalist. According to the research on tarantulas by the University of Miami in Ohio, larger tarantulas have never been eaten by female spiders after mating. Smaller male spiders have an 80% chance of being eaten by female spiders during mating.
The research paper holds that body shape is the main reason of sexual cannibalism. If the male is younger than the female, the probability of sexual cannibalism is higher, and if the male is older than the female, the probability of sexual cannibalism is lower.
This is also obvious in mantis.
By comparing the body shapes of the male mantis and the female mantis, we find that the male mantis is obviously smaller, so in terms of strength, the female mantis can easily catch the male mantis and eat it. It's easy for the male mantis to avoid being eaten. Some male mantis will choose the female mantis who has just finished preying to approach and mate with it. Or mate with it carefully and choose to run away immediately after mating.
In short, when mating, the male mantis is trying to avoid becoming food for his companions.