How to sex a spider...

Another vile rainy day, so I decided to make a cake to use several over-ripe bananas. When I lifted the mixing bowl from the cupboard I found this handsome beast captured inside. He's a male nursery-web spider Pisaura mirabilis. By rights he lives in the garden - but perhaps he's fed up with all the rain too.

You might wonder how I know he's a male. Well mature spiders are relatively easy to sex - if they have large 'boxing gloves' they're male. Almost all spiders reproduce sexually and are unusual in that they don't transfer sperm directly, for example via a penis. Instead the males transfer it to specialized pedipalps (boxing gloves) and then meander about to search for a mate. These palps are then introduced into the female's epigyne.

This was first described in 1678 by Martin Lister. In 1843 it was revealed that males build a nuptial web into which they deposit a drop of semen, which is then taken up by the copulatory apparatus in the pedipalp. The structure of the copulatory apparatus varies significantly between males of different species and is the main character used to identify some of the smaller and less patterned species, such as the money spiders.

Males nursery web spiders have another useful piece of behaviour. They offer food gifts to potential female mates and some have also been observed to feign death, remaining still while holding the food gift in their mouths. When the female approaches and tries to take the food away, the male springs back to life and attempts to mate. The strategy of playing dead more than doubles a male's odds of successfully achieving copulation, from 40% to 89%.

Finding this spider was probably the highlight of the day. Otherwise it was fairly humdrum, though our next-door neighbour brought her grand-daughter round to meet the chickens and look at some of Pete's insect collection - she was very impressed. And we got the good news that Chris is off to the Arctic again in the summer to do a two week research contract - but this time all his travelling expenses are being paid!