Black Widow Myth Reversed
We've all heard of the dreaded Black Widow — no not the Marvel comic super hero, but the infamous spider with a deadly bite that is mainly known for it's sexual cannibalism. Not only do black widow spiders have a venomous bite (with females being up to three times more venomous than males), but the female really lives up to her "black widow" namesake as she will often eat her male partner after mating.
However, a new study has shown that the tendency to consume a potential mate is also true of some types of male spider. The study by Lenka Sentenska and Stano Pekar from Masaryk University in the Czech Republic finds that male spiders of the Micaria sociabilis species are more likely to eat the females than be eaten.
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. Also, researchers observed this reverse cannibalism most often in July when the males from the summer generation were biggest, and therefore more cannibalistic. This would suggest that male aggression may be related to male size. Also, these larger males preyed on old females from the previous spring generation. This suggests they may have based their choice on female age. Female body size, even though considered to be a sign of quality, did not affect rates of cannibalism.
The authors remark: "Our study provides an insight into an unusual mating system, which differs significantly from the general model. Even males may choose their potential partners and apparently, in some cases, they can present their choice as extremely as females do by cannibalizing unpreferred mates."
The paper is published in Springer's journal Behavioral Ecology and Sociobiology.
Read more at Springer.
Black widow image via Shutterstock.