Spiders lure bees for dinner by making flowers look flashier

Life 10 July 2017
crab spider on a flower

Dinner time

Kim Taylor and Jane Burton/Getty

Ambush hunters normally rely on the element of surprise, opting to stay hidden until the moment of attack. But some spiders go for a flashier strategy. They reflect UV light, which makes the flowers they sit on appealing to bees – a bizarre strategy that has evolved multiple times in crab spiders, which ambush their prey instead of catching it in webs.

Felipe Gawryszewski at the Federal University of Goiás in Brazil and his team collected individuals from 68 species of crab spider in Australia, Europe and Malaysia. All of the species hunted insects using a sit, wait and pounce strategy, but some did so on drab substrates like bark and leaves while others hunted on flowers.


Using genetic information from all these species, the team pieced together a “family tree”, which showed that the flower-based hunting strategy evolved multiple times. What’s more, flower-dwelling crab spiders reflected more UV light than non-flower dwellers.


Floral guide

It’s not clear why bees are lured in, but one possibility is that they mistake the spiders for “floral guides” – natural bright spots on flowers that guide pollinators to the landing platform.

Another possibility is that bees have some preference for certain colour patterns, and spiders are tapping into that, says Gawryszewski.

But he also notes that there could be a downside to this strategy. As a UV reflecting spider, “you would potentially attract more prey, but you could also attract more predators.”

Scientists had previously suspected that UV reflectance in crab spiders was tied to the evolution of a flower-based hunting strategy. But this is the first study to back it with evidence using genetic information, says Jerome Casas at the University of Tours in France.

Journal reference: Evolution, DOI: 10.1111/evo.13271

Read more: A spider that looks and smells like bird droppings

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