And the male seems to be asking for it. In both of these species, he offers himself to her, somersaulting into her mouth after copulation. How he approaches her could mean the difference between life and death. Scott is conducting a research project to illuminate the antics of the male black widow, the neglected character in the mating drama.
It turns out the males are far from innocent bystanders, according to Scott. During peak mating season, thousands of males will prowl around looking for females.
Females set up their webs, stay put and wait. Female black widows use pheromone-laced silk to attract males. The scent tells the whole story of her mating history and even includes her hunger level.
Once the male arrives at her silken abode, he starts to wreck it, systematically disassembling her web one strand at a time. In a process scientists call web reduction, he bunches it into a little ball and wraps it up with his own silk.
The researchers suggest that in the Micaria sociabilis species, reverse cannibalism seen may be a type of male mate choice. The researchers collected male and female Micaria sociabilis spiders over a two-year period and studied their behavior by mixing males and females of the species at different time points. All spiders were well fed to discount cannibalism due to hunger. The authors observed what happened when they paired young adult male spiders with single female spiders either from the same generation young female or from another generation old female.
By pairing males with females of different size, age and mating status, the researchers hoped to be able to identify whether the reversed form of sexual cannibalism was an adaptive mechanism for male mate choice. Their study found that cannibalism took place early after the first contact and before any mating took place. The researchers also observed that reverse cannibalism differed significantly, depending on what month it was -- most of the incidents were in July.
Males from the summer generation tended to be bigger than males from the spring generation and they were more cannibalistic. This would suggest that male aggression may be related to male size. I told her to go away and isolate the females and watch to see if they produced viable eggs. She did. And they did. The males were clearly mating with them though, and when they did, they almost never offered themselves up as snacks. When Andrade talked about the discovery at a conference, she learned that another student, Iara Sandomirsky, had seen the same behavior in another closely related spider—the brown widow.
These grisly acts clearly damage the females. The males certainly benefit. When one mates with an immature female, he is more likely to fill both storage organs and plug them, preventing later suitors from displacing his sperm.
As for the brown widows, a whopping 80 percent of males get a second shot at mating if their first partner is immature. Possibly because doing so is tricky, says Andrade. It means finding females during a narrow window when their genitals are internally ready but not externally open.
Still, this happens frequently enough that a third of female redbacks seem to mate before they are fully mature. All rights reserved. But for two particular species—the Australian redback spider and the brown widow—the male gives them a helping hand. In mid-coitus, he flips over and offers his body to be eaten, all for the chance that she'll bear his children. And you thought paying for an expensive date was uncool.
It's one of the most extreme, one-sided mating patterns in nature. By almost all accounts, the female, who weighs up to times more, has the upper hand. Or does she? Now, researchers have found that the male has some tricks of his own up his eight sleeves. Male redbacks and brown widows often go for females who have yet to reach full maturity—and who tend not to eat their mates. This way, the male gets to be the first to inseminate her, increasing his chances at fertilization.
Better yet, he lives to mate again. So basically, the males don't have to be sexually cannibalized, and don't have to worry about having females that are too choosy. You basically have females with no resistance to copulation at all.
You bite her open, mate with her, and wander away. That's right, the male has to bite her open—her exoskeleton, anyway.
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