We've all heard of or possibly even been unfortunate enough to see black widows, with their notorious habit of eating their male sexual partners after mating. But what about the male black widows? Do they ever eat females?
It turns out that researchers have discovered that black widows don't always eat their mates after sexual intercourse, and that indeed there are some male black widows that eat their female counterparts subsequent to coitus.
"Sexual cannibalism," as LiveScience puts it in an article published on Monday, May 6, is a way for some female black widows to assert their "partner preference" by chasing inferior males down and devouring them after the sex act is completed.
A species of black widow called Micaria sociabilis, however, exhibits the rather specialized feature of male black widows putting the sexual switch on the females and eating them, instead of vice versa.
Researchers at the Czech Republic's Masaryk University conducted a study in which black widows from the Micaria sociabilis species were well-fed enough to hopefully alleviate the need for cannibalism. At least not "hunger-driven" cannibalism.
What the scientists discovered is that the male black widows in the study would eat the females, often after first contact and before any sexual activity. The cannibalistic male black widows were more likely to be born in the "summer generation" than those born in the "spring generation," meaning that the larger male black widows were more likely to turn cannibalistic and that size therefore may impact aggression.
Age may also be a factor in male black widows turning cannibalistic, the researchers found. When the younger male black widows from the summer generation made contact with the older female black widows from the spring generation, the sexual switch with cannibalism was more likely to occur.
The male black widows from the Micaria sociabilis were also not interested in virginity or body size when it came to staving off cannibalizing female black widows, the researchers discovered — which is an odd behavior considering those two factors tend to be very important in mating preferences for the arachnids.
"Our study provides an insight into an unusual mating system, which differs significantly from the general model," researchers Lenka Sentenska and Stano Pekar wrote in the journal Behavioral Ecology and Sociobiology. "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," Sentenska and Pekar said.
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