Cellar spider catches a woodlouse (arachnophobes look away now)

 

The cellar spider Pholcus phalangioides is a welcome guest in our house. In summer it's a very effective fly killerand it also catches and eats much larger spiders, of the kind that sometimes turn up in the bath or race across the ceiling and floor when the cold weather brings them indoors, in autumn. A few cobwebs in corners of the ceilings are a small price to pay for these services.

Sometimes these spiders catch woodlice, which is what this one has trapped in its web, alongside a fly that has already been encased in silk. But this woodlouse was a prize catch, because its a female that was carrying baby woodlice, known as mancas, in its brood pouch, under those armoured plates. They are the tiny translucent woodlice, as yet with no hardened armour, that you can see in the photograph below.

Female woodlice carry their young in a brood pouch under their body, and at this stage the young only have six pairs of legs. After their first moult they develop an extra body segment and after the second moult they grow an additional pair of legs, so they are then classified as juveniles with the full adult complement of seven pairs of legs.

For a closer look at woodlice, check out my Beyond the Human Eye blog here.