Smaller than the tip of a typical ballpoint pen, spider mites are microscopic arachnids that are distant relatives of spiders. These eight-legged animals inhabit big groups and devour plants by puncturing the tissues with their pointed teeth and sucking the liquids out.
Since female spider mites only use the sperm from the first male they mate with, living in close quarters can lead to intense competition for mates. For the duration of their lives, they even keep this sperm in a unique internal pouch to fertilize their eggs.
A male spider mite must mate with a female first in order to pass on his genes; thus, males have devised tactics to increase their chances. Males will defend almost all adult females so that they are ready to mate as soon as the females are ready.
Some males defend the almost adult females from rivals who approach them, while others—dubbed “sneakers” by researchers—lie in wait covertly.
The males rush in as soon as the female removes her old skin and emerges as an adult. The mating habits of spider mites are investigated by Dr. Peter Schausberger is a professor at the University of Vienna and a leading researcher in the field of arthropod behavioral ecology.
When he and his colleagues observed something odd happening, they were watching a video that had been captured using a digital microscope.
Peeling Back Arachnid Courtship
According to Schausberger, who was the paper’s primary author, “we observed that the guarding male becomes highly active and begins to pull on the skin of the female and strip it off.”
To reach the genital entrance, “the males then pull off the hind parts (of the skin)” and conduct the deed.
There isn’t enough time to completely strip, so “sometimes they copulate when the front part (of the female) is still covered,” he added. Although the procedure may seem horrifying, according to Schausberger, the females are not harmed since the dead skin the men remove would fall off on its own without their assistance.
In the lab, Schausberger and his coworkers observed the mites as they undressed. The scientists discovered that the molting process moved more quickly, and the males’ chances of being the first to mate were increased when the males assisted the females in shedding their old skin.