So the females bite the heads off the males, and later the whole body, but the male’s body finds it’s mating spot and continues to mate for hours
Attenborough describes as hormones and enzymes being responsible, and that the female derives much energy from this exchange resulting in more eggs, but why are they driven to do so?
What selection pressures would select for this? There are other insect species that don’t need to consume their partner, nor do they need the extra energy. The male being able to mate after being headless would also have been selected for? I don’t understand why this would be the case
In: Biology
Just as a preamble, sexual cannibalism is not observed in the vast majority of mantis species, and in those species in which it does occur, it’s more likely not to happen.
That said, it *does* happen in the wild, with a rate of around 1/3rd of all copulation involving cannibalism in some species ([cite](https://www.sciencedirect.com/science/article/abs/pii/S0003347205810176)). And it’s *not* a winning strategy. A [recent study](https://royalsocietypublishing.org/doi/10.1098/rsbl.2023.0505) found that sexual cannibalism, particular before mating, dramatically reduces genetic diversity and population levels. Reduced diversity means reduced opportunities for selection, which means more mutations will be propagated, which is even *worse* for the survival of the population.
So sexual cannibalism seems to be a *really bad* thing for species that practice it. So why do it?
It may be that it is advantageous for the offspring of the female to a degree significant enough that it’s worth sabotaging the entire species. We see similar behavior in some mammals which will kill and sometimes eat the young of their own species; it’s bad for the species/local population as a whole, but good for the offspring of one individual.
Or it might just be a behavior which has been selected for but is not maladaptive, like the extreme reluctance of pandas to mate. Not all behaviors are positive ones.
Since the genetic research I linked to above was published just a few months ago, it seems as though this is an unsolved question in biology which is being actively researched.
KISS – Keep It Simple, Stupid
No need to “code” different behavior between “being a Mantis and eating anything that moves” and “don’t eat this thing, it gives me sperm”
As a programmer, I admire the simplicity
I did time as a fire ant (S. invicta) researcher. Not the same, but fire ant and some other ant species only use males for a short time, they fly high in the air, copulate, and fall to the ground dead while the females become queens. You can find them on the ground looking for a colony spot in the hot summer a day after it rains.
I would think maybe the praying mantis is the same way, where a male is alive much longer, but has the same eventual function as a male fire ant: copulate and then it’s job done. I would figure single use means that you don’t have to have sperm constantly being made, and the sex organs could be in a dormant state, all until it’s time. This would make for a lighter, leaner hunter. Praying mantises are carnivores.
Here’s a short encyclopedia article on the subject unrelated to anything I said: https://www.britannica.com/list/6-animals-that-eat-their-mates
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