This is a very small spider. The male has a 2 mm body length and is smaller than the female which has a 3 mm body length. The uniformly orange-red abdomen is most distinctive, whilst the head is darker almost back. There is also a blackish patch at the rear of the abdomen which is probably best seen from beneath. There are no other spiders with a similar appearance.

O. melanopygius occurs in a very wide range of habitats, particularly rubbish heaps and gardens, under stones etc and occasionally occurring indoors.

All year but mainly found from spring through to autumn.

Distribution: The species is widespread but patchy in much of England, and very scattered elsewhere in Britain.

Fairly frequent in Leicestershire and Rutland.

https://srs.britishspiders.org.uk/portal.php/p/Summary/s/Ostearius+melanopygius