The Spider Sexual Battlefield

October 13, 2010

Torah Kachur

Generally, sex is a risk free pastime of many people - we've got the pill to prevent pregnancy and condoms to prevent disease.  And, we don't need to worry about decapitation at the end.


Not true for a male orb spider.  If the woman's thirst for sex isn't satisfied, she satisfies her belly by eating him.  Talk about sex wars.


Mmmmmm.... previous sex partners are yummy

          Torah Kachur Science in Seconds Sexual cannibalism orb spider argiope


The cannibalistic behaviour of the female orb spider seems like the ultimate price to pay if you aren't good in the sack.  But, the research suggests otherwise: male spiders that can copulate for longer are actually the ones that get sacrificed.  The 'premie' spiders can have sex, deposit sperm and take off before she gets annoyed.  So it's the ones that can last that become lunch.


The reasoning is simple "Females should always cannibalize a male".  That is probably the wisest thing ever said in a piece of scientific literature.  What it really means is that it is advantageous for a female to eat mates because it provides a source of food and therefore improves the fecundity of the female by ensuring she is nice and well fed.  He could also just cook for once, but researchers haven't explored that yet. New research published this week in Biology Letters suggests that the degree of relatedness also influences mating time and whether he becomes the next meal.  In an experiment akin to the next MMA fighting championships or cock-fighting, researchers got to put a female Argiope spider with either a sibling or non-sibling males.  And then they got to watch!



Did he survive?  Did he copulate?  Who won?


Winning is maybe in the eye of the beholder on this one.  When females mated with their brothers, the brothers were obviously disgusted at the prospect and had reduced mating time which allowed them to escape sexual cannibalism.  While unrelated males were a bit more enthusiastic and mated longer....resulting in their ultimate demise.  The researchers concluded that spider-sex-fighting will be the next wave of online betting matches, and that the brothers survival allowed him to go off and find a more appropriate mate.


Sexual cannibalism is not common in nature, resulting in comments from great evolutionary biologists like Stephen Jay Gould to claim that it's importance is overestimated.  However, it's pretty cool and it is sure to make females of many species a little bit jealous. 


"Oh...... hi honey.. love you"


Welke, K., & Schneider, J. (2010). Males of the orb-web spider Argiope bruennichi sacrifice themselves to unrelated females Biology Letters, 6 (5), 585-588 DOI: 10.1098/rsbl.2010.0214



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