Maybe they just needed some contouring and a little more mascara?
Researchers have found a strange-but-effective tool to test the theory that male jumping spiders evolved colorful stripes to ward off predators: makeup.
Scientists writing in the journal Royal Society Open Science wanted to establish whether male spiders of species Habronattus pyrrithrix are protected, thanks to their bright, striped backs. Male jumping spiders, unlike females, have bright and vivid coloration to attract mates.
Using makeup to paint the backs of both male and female spiders, the researchers made each sex look like the opposite to determine whether that would change the behavior of a much larger jumping spider, the predatorial Phidippus californicus.
Researchers dimmed the back stripes of males using foundation powder under a microscope. Black stripes were drawn on the backs of females using Urban Decay’s black liquid eyeliner.
The experiment used (a) a sham-control male (male behavior + male coloration), (b) a female painted like a male (female behavior + male coloration), (c) a male painted like a female (male behavior + female coloration) and (d) a sham-control female (female behavior + female coloration). Collette Cook et al.The team hypothesized that “the sexually dimorphic dorsal color patterns” would be most effective at deterring predators when paired with sex-specific behaviors. That coloration, along with behavior in which they raise and wave their first pair of legs while searching for females, was predicted to help them avoid predators.
However, that was not the case. Regardless of their sex, jumping spiders with stripes on their back actually had an increased chance of being attacked by the larger jumping spider species.
Additionally, male jumping spiders were more likely than females to be captured by the predator and were captured sooner than females — regardless of coloration.
Regardless of their actual sex, spiders with male-like dorsal patterns (stripes) were attacked more often by the predator than those with female-like patterns (no stripes). Collette Cook et al.“Habronattus pyrrithrix is a sexually dichromatic jumping spider; males have bright red faces and green front legs that they display to cryptically coloured females during courtship,” the researchers had suggested in the study. “This conspicuous colour pattern and behaviour may offer protection for males that are highly active and constantly moving through the leaf litter as they search for females.”
The researchers were left with two possible conclusions: either the hypothesis about stripes is still valid for other predators but not P. californicus, or the color patterns evolved for a different reason.
While unlikely, possible reasons for those color patterns include disruptive coloration — a form of camouflage using contrasting markings to break up an animal’s outline — or motion dazzle, in which “the constant movement and leg-waving of males attracts attention to the head of the spider,” according to the study.
“We should also remember to consider the possibility that male color patterns may not have an adaptive function at all,” the study added.
As for actually testing with arachnid makeovers in the lab, University of Florida study author Dr. Lisa Taylor seemed satisfied with the quirky technique.
“I had never really thought as much about makeup until I started studying spiders, but when you apply the makeup … and you can see how cleanly and how finely it goes on — it’s not quite as intricate as like painting a grain of rice, but sometimes it feels that way,” she told the Guardian.
