And what about the male’s famous ability to “keep the beat” even after losing its head? Biologists Eckehard Liske and W. Jackson Davis have an explanation for that phenomenon as well. They believe that, rather than acting as a stimulus for copulation (by releasing sexual movements), decapitation artificially induces the behavior. This would be similar to the way in which lopping off a chicken’s head artificially induces locomotor movements that can temporarily propel a headless bird around a barnyard. According to these researchers, from an evolutionary perspective, reflexive abdominal contractions and the subsequent release of sperm may insure that fertilization takes place, even if the males are left feeling a bit lightheaded after sex. As such, it serves as a prime example of how cannibalism can benefit the individual being cannibalized.
As in the praying mantises, in certain well-known spiders, truth has been masked by myth. After several papers in the 1930s and 1940s reported that female Latrodectus mactans spiders devoured their mates after copulation, L. mactans and two additional North American species became widely known as black widows. Although most of the initial observations turned out to be anecdotal, cannibalism and black widows became forever linked, appearing in an array of literature that ranged from storybooks to college textbooks on evolution, ecology, and animal behavior. The cannibal association continued through the 1970s and 1980s, even though researchers working with these spiders were beginning to discover that the behavior in black widows was actually a rare occurrence. They determined that not only did most male spiders depart unharmed after copulation, but some of them lived in the female’s web for several weeks, even sharing her prey.
“The supposed aggressiveness of the female spider toward the male is largely a myth,” said spider expert Rainer Foelix. “When a female is ready for mating, there is little danger for the male.” Foelix did add that all bets were off if a male mistakenly showed up in the web of a hungry female.
Readers who might be disappointed to learn that the black widow’s reputation is apparently worse than its bite may be consoled by the fact that sexual cannibalism has been reported in 16 out of 109 spider families (although the list is described as not “exhaustive nor definitive” regarding frequency). One of the most interesting examples takes place in the black widow’s Aussie cousin, the redback spider (L. hasselti). In this species, males go to extreme lengths, not only to guarantee their own demise, but their consumption as well.
The Australian redback spider is common throughout Australia, and in a country renowned for its notorious creatures, the redback ranks among the most dangerous. The reasons behind this spider’s bad reputation start with a neurotoxic bite that can cause severe pain and swelling, and in rare instances, seizures, coma, and even death. Like the North American black widows, Australian redbacks are often found in close proximity to human residences, especially sheds and garages offering the spiders undisturbed areas full of clutter. Presumably because of the abundance of flies, both black widows and redback spiders were once common in outhouses, where their fondness for living under privy seats was never quite as unpopular as their habit of biting anything that blocked their escape routes. Slim Newton’s song “Redback on the Toilet Seat” details one such encounter. “There was a redback on the toilet seat when I was there last night—I didn’t see him in the dark but boy I felt his bite.” The song reached #3 on the Australian pop record charts in August 1972, well ahead of artists like The Bee Gees and Elton John.
Although encounters with humans are rarely fatal (at least for the human), the same cannot be said for male redback spiders attempting to mate. In the first stage of courtship, the male approaches the female’s web and proceeds to get himself noticed (which takes a bit of doing, since he is only about one-fifth her size). He does so by bouncing his body up and down, throwing some silk around, and waving his front legs. As a point of information, while insects have six legs, spiders have eight of them, plus an additional pair of anteriorly located appendages called pedipalps. In male spiders, the pedipalps are modified for transferring sperm to the female’s body, a chore necessitated by the fact that spiders lack penises. Furthermore, there is no internal connection between the pedipalps and the testes, which are located within the abdomen. Instead, sperm is initially extruded from a furrow on the male’s abdomen into a spun receptacle called a sperm web. As a male dips his pedipalps into the pooled sperm, a pair of coiled structures called emboli and their associated muscles work like tiny turkey basters to suck up the liquid and store it until copulation.
The next phase of redback courtship begins as the male initiates repeated bouts of physical contact with his potential mate, behavior that includes tapping, probing, and nuzzling. The real heavy petting begins once the male locates the female’s epigynal opening. According to spider expert L.M. Forster, this behavior includes “nibbling, palpal boxing, and knocking, embolus stretching, push-ups, abdominal vibration, and epigynal scraping.”
By now, if the female hasn’t already eaten the male (which can put a serious dent into all of this foreplay) the spiders briefly assume “Gerhardt’s position 3.” To visualize this, picture two people in the missionary position. Now tweak the imagery a bit so that the guy is approximately the size of your favorite throw pillow. Okay, now add another eight limbs. (All right, maybe you shouldn’t picture this.)