Friday, February 3, 2012

Crafty Crab Spiders

Some spiders spin webs, others chase down their prey, a few leap on victims - but crab spiders have an altogether more laid-back approach to hunting. They just sit on a flower with their front legs akimbo like a crab, keep perfectly still, wait for a visiting insect to land within reach - then grab it. Using the pollen and nectar supply of the flower as their lure, they are remarkably effective hunters. 

I think all of these, except the last one, are Xysticus species and all females - probably two different colour morphs of the same species, X. cristatus. Notice those forward-pointing bristles on the outspread legs which help to grip the struggling prey when those legs close around it.

The fly visiting this dandelion is living very dangerously.

The host flower here is viper's bugloss Echium vulgare, a plant that produces a lot of nectar and so is a magnet for potential prey.

All the above are scanned transparencies taken in our garden a decade ago, but the final one was taken in France 30 years ago and shows Misumena vatia, which can change colour to match its floral background. This female tones very nicely with the hemp agrimony inflorescence that she's sitting on - notice the perfect colour match of the pink patches on the flanks of her abdomen and the flower buds.