In the competitive and weird world of spider mite mating, there’s no time to waste as evidenced by the discovery that males will crack open the juvenile skin suits of developing females to speed things along. Not content to wait for the females to shed dead skin themselves, the males have evolved to spot the silvery appearance of females who are on the cusp of sexual maturity and lend a helping hand in getting them undressed.
“Our study documents an exceptional male behavior in the animal kingdom, namely that male spider mites strip off the skin of premature females that are close to molting into adulthood,” said Peter Schausberger from the University of Vienna, in a statement.
“Such undressing behavior by the male is adaptive—that is, it increases their reproductive success—because it would be an enormous cost to the guarding male if a rival would take away the female and inseminate her instead of the male that invested time and energy in guarding her. The guards would have invested hours in guarding a potential future mate without any reward.”
Only the first male to mate with a female will sire any offspring, and all of the fertilized eggs that hatch will be females – males are actually the product of unfertilized eggs. This means the competition is really on to be at the front of the queue, and as a result, males will guard near-ready females for hours before things kick off.
Spider mites, like many insects, shed layers as they develop and when their mating-ready body is done developing, the surrounding layer of “exuvia” will start to turn silvery as air fills the gap between the two. The color change triggers an unusual response in the guarding males.
“Sometimes they drum with their forelegs on the females, possibly to stimulate the females to initiate the molting process, and make the females bulge and crack the exuvia,” Schausberger explained.
“Upon cracking the exuvia, the guarding male becomes highly active and pulls on the hind part of the old skin with his pedipalps until it is removed from the female body and the genital opening of the female, which is located on the underside of the tip of her abdomen, is exposed so that the male can slip beneath the female and insert his aedeagus. Females that are undressed by a male first get rid of the hind part of the old skin because of male pulling, whereas females that molt without the help of a male first pull out from the front part of the old skin.”
Hurrying along the molting process in this way increases the male’s chance of reproductive success, making it a remarkable strategy born out of sexual selection. It was actually discovered somewhat by accident as Schausberger and colleagues were observing male and female interaction to study alternative reproductive tactics when they noticed the “undressing” behavior.
And they say romance is dead.
The study is published in the journal iScience.