As I have observed animals, birds, and animals, I have noticed that sometimes the male is larger than the female and sometimes the opposite is the case. Quite often the size difference is so slight that you have to rely on other characteristics to try to determine the gender of a subject.
When it comes to spiders, though, the size difference is shockingly large—the male is often one quarter the size of the female or even smaller. On Monday I spotted my first black and yellow garden spider (Argiope aurantia) of the season. I have long been fascinated with these large spiders and the distinctive zigzag pattern that they weave into their webs.
When I looked at my images on my computer, I was surprised to see that there was a second, smaller spider just to the left and behind the main subject. Could this possibly be a male garden spider? According to Wikipedia, males range in size from .2-.35 inches (5-9 mm) and females range in size from .75 to 1.1 inches (18 to 28 mm), so the size differential seems about right. Additional the smaller spider looks like photos I was able to find of male garden spiders.
Spider mating can hazardous for male spiders. In some species, if the male is rejected by the female, she eats him. I thought that might be the case for these garden spiders, but came across a fascinating article at newscientist.com with the sensationalist title “Spider sex causes spontaneous death” that suggests something stranger than cannibalism.
According to a study conducted at Concordia University and the University of California, “Researchers found that for male orb-weaving spiders of the species Argiope aurantia completing copulation leads to certain death. The deceased suitor’s corpse is then trapped in the female genitalia. This may be a strategy to prevent other males from subsequently mating with the female, say the scientists.” The scientists determined that the female did nothing to kill the males who died spontaneously and concluded, “The females do sometimes remove and devour their dead mates. But the researchers do not think the death program evolved to give her a post-sex snack, as the males are too tiny to provide much nutrition.”
Nature can be wild, weird, and wonderful and endlessly fascinating. I guess that is what prompted the scientists to carefully study 100 pairs of spiders mating. 🙂
© Michael Q. Powell. All rights reserved.
Read Full Post »
Mike Powell 