As always, animal porn is under the fold:
Actually, there are many species of praying mantises and in most of them sexual cannibalism is quite rare. It occurs much more often in the laboratory than out in the field. Apparently, the lights and sounds of a laboratory are stressful to the female so she acts aggressively in response.
The praying mantises are very aggressive predators and they can eat quite a lot of food, preferring soft-bodied insects (like flies), but not turning their heads away from cockroaches, snakes....
.... or other mantises, including males of their own species:
The male may be eaten before, during or after the copulation. Male is a great source of protein, so eating him afterwards makes sense for the female:
In only one species, the Mantis religiosa, does it appear that decapitation of the male actually may be neccessary for successful copulation. The removal of the male's head triggers reflexive copulatory motions, resulting in faster ejaculation - why that increases females's fitness is not clear.
A female may eat a male before copulation, especially if she is hungry, the male is small and it is early in the breeding season - he is worth more as food than as sperm donor at that stage.
Videos from out in the nature, though, more often than not, show elaborate mating behaviors and successful escape by the male afterwards. Sometimes they may even engage in a threesome:
While in some other animals there is an advantage for the male to be eaten after mating, such an advantage was not shown in praying mantises. A recent study shows that male mantids prefer not to be victims of sexual assault after all. But sometimes, when she is hungry and you are a lousy lover, that is what you get....
In only one species, the Mantis religiosa, does it appear that decapitation of the male actually may be neccessary for successful copulation.
It's been a while since I've kept up with the mantid literature, but I recall that decapitation isn't really necessary for copulation; it merely removes the ganglion responsible for inhibiting copulation. So, the male can mate just fine with his head still intact, but if he moves through the female's visual field in such a way that she decides that he's food, she can decapitate him without bringing the festivities to a complete halt.
I love the plastic models, though!
"This behaviour pattern, in which she devours the male, is of obvious advantage to the female, and to the species, because she is able to put to good use an otherwise worthless mass of protein." [snip]
"Not only does the female of the species not value you for your mind; by the time she gets done with you you don't even HAVE a mind."
I couldn't help but burst out laughing.
I wonder if faster ejaculation would make it less likely for the female to be eaten by something else.
I was trying to find some more info on that. Apparently, the mating is quite a long process, indicating that it is not so dangerous to the mantids in the first place (i.e., there is a reason why rabbits are so fast). They take their time, hidden under the leaves and stuff. I do not know by how much does copulation shorten upon decapitation and if that would make any difference on her survival rate, or perhaps on the quantity/quality of sperm she gets.
I was not absolutely sure if decapitation is neccessary in M.religiosa, but this is the only species in which decapitation appears in a large percentage of matings and the behavior has been well documented. I am wondering how inhibited the mating behavior may be with the head still on - I'd be probably quite inhibited myself if I was in such mortal danger LOL!
I actually videotaped the mating process last fall for posterity and for our homeschoool. Some mantises were on a bush outside my front door. I was curious to see if the female (much larger than the males) would eat her mate, as I'd read she would, and was surprised to see her mating with two at a time; one male waited patiently on the back of the other 'til it was his turn! And, I was disappointed to see they both got away scot-free! The process looked so painful for the poor female. The male seemed to insert his entire abdomen inside hers! So I thought if survived that and ate him, he deserved it! The mating ritual and mating process took a loooonnnngggg time. over 24 hours, I believe. When I figure out how, I'll post the video on Youtube.