Monday, 5 October 2015

Uloboridae: Cribellate orb-weavers

 Although not a particularly small family, only three species of Uloboridae are found in the UK, one of them, Uloborus plumipes only a recent colonist. They are very unusual spiders in many respects. The Uloboridae are cribellate spiders, they produce many fine threads which they comb using a structure on their rear legs formed by a row of short bristles, resulting in characteristic wool-like or frizzy threads.
 Uloborus plumipes the 'garden centre spider' (above) is typically found only inside garden centre heated glasshouse, and rests with her oversized and spiny forelegs together ahead of her, looking like a piece of debris on her orb web.

No venom
Another unusual feature is that, unlike most other spiders, they have no venom glands: they rely on quickly wrapping prey on silk and only bite once the prey is so immobilised.

Orb weavers
The orbs produced by Uloborus plumipes have a striking resemblance to Araneid webs, although other members of the family have more unusual asymmetric webs. Despite this, they appear to have evolved orb-weaving independently of the Araneae.
The orb web of Uloborus plumipes
The resting Uloborus with its characteristic posture on its orb-web.
The unusual spiky egg sac of Uloborus plumipes, which looks like a shrivelled piece of leaf or seed. You can see the woolly texture of the silk threads securing it.

2 comments:

RayHolden said...

I'm totally and utterly enjoying these Arachtober postings.
I'm learning a lot!

Africa Gómez said...

Thank you so much Ray! much appreciated :-)