The brown huntsman spider, Heteropoda venatoria, has a striking white stripe on its face reminiscent of a moustache. And now, researchers who’ve shaved those spider moustaches off have discovered that the vibrant bristles help lure flying insects to their death in the dark. The findings were published in the April issue of Animal Behaviour.

Coloration plays an important role in animal visual communication, and predators are known to attract prey using visual signals like bright body hues -- though this strategy is typically used by animals who hunt in the daytime. Studies on using bright body coloration to lure prey often ignore nocturnal predators: You just don’t expect this foraging tactic to occur in low lighting.

Now, to investigate color-mediated prey attraction in a nocturnal predator, a team led by I-Min Tso of Tunghai University conducted field experiments with both dummies and real brown huntsman spiders. Using infrared video cameras, the team monitored the responses of nocturnal prey to normal spiders and spiders with the white stripe removed. (These were gently shaved off of anaesthetized spiders.)

With both dummy and real spiders, they found, an intact white ‘stache significantly increases the attraction rate of nocturnal prey. Even at night, the conspicuous moustache coloration acts as a visual lure for flying insects like moths. The white hair reflect light differently from the rest of the body, and the bright coloring seems to confuse flying insects. “It is highly possible that the moths have mistakenly regarded the white coloration as a nocturnal blooming flower during their foraging at night," Tso tells New Scientst.

As with many other instances of bright body coloration in the animal kingdom, the moustache might play a role in sexual selection. The team's now looking at the stripe from the perspective of mate choice.