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In spite of the fact that among many insects and animals the law dominates that it is necessary to start "families" with young individuals, zoologists got confused in sexual behavior of black widows. The matter is that their sexual preferences differ from other arachnoid a little. Males of spiders of a family of black widows give preference to pairing with more elderly females though it is improbable to receive posterity with them, and here risk to be destroyed increases.
In a research the representatives of a family of black widows living in the territory of North America — spiders of Latrodectus geometricus became experimental. This type of arachnoid is poisonous and practices sexual cannibalism where males who by the nature have the smaller sizes become the victims of sexual intercourse. After copulation the female eats a spider-osemenitelya.
In spite of the fact that zoologists got confused in behavior of black widows at sexual intercourse, they managed to find out that similar "self-sacrifice" facilitates to a male pairing process. In exchange the female receives a certain stock nutritious substances, simplifying the procedure of incubation of posterity.
The similar fact is known to biologists about mantises for a long time. As for black widows of a type of Latrodectus geometricus, It should be noted the following population features:
So strange behavior caused interest from the Israeli zoologists who decided to deal with sexual dimorphism and other strangenesses. It turned out that males of black widows prefer to copulate with older females, despite their reduced fertility.
At the same time the probability to be a tasty breakfast considerably increases. To this conclusion the Chevy Vaner (the author of the project) with the colleagues came, and their conclusions were published on pages of the edition of the Animal Behaviour magazine.
During the experiment scientists managed to find out that young females of the black widow long stay in a condition of an unripe phenotype , than favourably differ from adult individuals. They are also capable to bear posterity, at the same time they do not need many nutrients, besides their sexual cannibalism is at the minimum level. More adult females are much more fertile. Old female spiders are less fertile, but are more gluttonous. It makes them not by the most suitable partners for pairing. Despite it, males give preference to old females .
Preliminary researches showed that it gives the chance to spiders to reject a penis of a pedipalp for the purpose of blockage of channels of females. In that case other males will not be able to impregnate it more. But laboratory this hypothesis was not confirmed.