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Spider cannibalism is the act of a spider consuming all or part of another individual of the same species as food. In the majority of cases a female spider kills and eats a male spider before, during, or after copulation. Cases in which males eat females are rare. ==Females eating males== It is often said that the male (usually significantly smaller than the female, down to 1% of her size as seen in ''Tidarren sisyphoides'') is likely to be killed by the female after the coupling, or sometimes even before intercourse has been initiated. This supposed propensity is what gave the black widow spider, ''Latrodectus mactans'', its name. However, the three species of North American black widows do not usually kill the male (although they have been known to do so). Males can sometimes even live in the web of a female for a while without being harmed in any way. The male Australian redback spider ''Latrodectus hasselti'' is killed by the female after he inserts his second palpus in the female genital opening; in over 60% of cases the female then eats the male. But the Black Widow female consumes the male after mating, usually the male gives a sacrifice. Although the male ''Latrodectus hasselti'' may sometimes die during mating without the female actually consuming him, this species represents a possible strategy of "male sacrifice." The male redback, while copulating, "somersaults" and twists his abdomen directly onto the fangs of his mate. Approximately 65% of males are consumed at this stage.〔Andrade, Maydianne C. B. ''Behavioral Ecology'' (2003), 14:531–538〕 Males that "sacrifice" themselves gain the benefit of increasing their paternity relative to males who do not get cannibalized.〔 Despite these examples and many other similar reports, however, the theory of the "sacrificial male" has become greater than the truth. Mating of spiders is not always followed by cannibalism. Indeed, scholars have noted that the "supposed aggressiveness of the female spider towards the male is largely a myth" and that cannibalism only occurs in exceptional cases.〔Foelix, Rainer F. ''Biology of Spiders'', 1982.〕〔Roberts, Michael J. ''Spiders of Britain and Northern Europe'', Collins, London, 1995.〕 Even so, spider cannibalism has been shown to occur in some species more than in others, mainly species belonging to ''Latrodectus''. There has always been speculation on why this sacrifice of male mates might occur despite the obvious disadvantage to the sacrificial males. One theory is that once the male has mated, he is unlikely to mate again and so any further extension of his life is of lesser evolutionary benefit than his indirectly contributing nutrition to the eggs. Having more offspring would give the male the advantage of having his genes passed on over other males that might avoid being eaten. This scenario would be consistent with Roberts’ hypothesis that old or unfit males get eaten, whilst younger and fitter ones may survive to mate again.〔 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Spider cannibalism」の詳細全文を読む スポンサード リンク
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