January 17, 2014
Male Black Widows Wiggle It To Attract Their Mates
[ Watch the Video: Black Widow Males Dance It Up During Mating Time ]
Lee Rannals for redOrbit.com - Your Universe OnlineBiologists at Simon Fraser University have discovered that male black widow spiders can 'twerk' like Miley Cyrus to attract females. According to a study published in the open access journal Frontiers in Zoology, male black widow spiders shake their abdomens to produce carefully pitched vibrations to let females know they are ready to court, and are not potential prey.
The researchers recorded the vibrations made by male black widow spiders, hobo spiders and prey insects, which included house flies and crickets.
“The web functions as an extension of the spider's exquisitely tuned sensory system, allowing her to very quickly detect and respond to prey coming into contact with her silk,” said Catherine Scott, a graduate student at the university. “This presents prospective mates with a real challenge when they first arrive at a female's web: they need to signal their presence and desirability, without triggering the female's predatory response.”
The team found that the vibrations produced by black widow and hobo spiders were different than those of prey. However, the low-amplitude vibratory signals male black widows produced while they shook their abdomen were more distinctive than the rest.
“Female spiders are fine-tuned to detect and quickly respond to prey vibrations, presenting a challenge to courting males who must attract a female's attention but not be mistaken for prey. This is likely particularly important at the onset of courtship when a male enters a female's web,” the researchers wrote in the journal.
Little is known about how males attract females in a web, particularly because vibrations felt in a web is a signal that prey has been caught. The team had to use Doppler vibrometry to study the vibrations produced by the males and prey on tangle webs of the western black widow Latrodectus hesperus and on sheet webs of the hobo spider Tegenaria agrestis.
The team said they recorded the vibrations at the location typically occupied by a hunting female spider, and compared the vibrations produced in terms of their waveform, dominant frequency, frequency bandwidth, amplitude and duration. They also played back male and prey vibrations through the webs of the female spiders to determine the vibratory parameters that trigger a predatory response.
“Unlike courtship signals of other spider species, the courtship signals of L. hesperus and T. agrestis males do not have complex temporal patterning. The low-amplitude 'whispers' of L. hesperus males at the onset of courtship are less likely to trigger a predatory response in females than the high-amplitude vibrations of struggling prey,” the team concluded in the journal.