The Oonopidae are hunting spiders. The drawing below shows the typical arrangement of their eyes as seen looking down from above the spider. Female spiders in this family do not have a sclerotized epigyne.
Although there are only 2 species in this family in the U. K., a few species have been recently introduced with plants, but can survive only in heated environments.
Above is Oonops domesticus, there are only two spiders in this family in the UK, this one which is generally found indoors, and Oonops pulcher which is generally found outside. Both look rather similar being small, between 1-2 mm long. The abdomen ranges from yellow, orange, red or pink, with a tan or brownish prosoma. They have just 6 eyes and no epigyne. Both sexes are similar.
Although they are found widely in the UK and Europe, they are rarely seen because of their small size, and also because they are active at night. They have a characteristic way of moving - they seem to slide slowly over the surface, and then move so speedily that you lose sight of them. They lay just 2 pinkish eggs at a time in a semi-transparent silken sac.
Below is a photograph of a mature male Pholcus phalangioides (daddy-long-legs spider). There are 969 species in this family world wide, but only 3 in the U. K. Most of them live in tropical caves. When they are disturbed they vibrate their tangled web making themselves appear blurred and difficult to catch. The drawing below shows a typical pholcidae head and the arrangement of the 8 eyes.
It is easy to see the spider below is a mature male as his palps are swollen so that they look a little like boxing gloves. The palps of the male act as secondary sex organs. The sperm is formed in the testes which are located in the abdomen. The fluid spermatozoa comes out of a very inconspicuous opening onto the web. The male then draws up the fluid into the palp, probably by capillary action. And it is the palp that is inserted into the female's epigyne during mating. It is the male who searches for the female, so it is more common to find wandering mature males than females. Copulation lasts several hours, and usually the male is not eaten afterwards.
There are usually around 20 eggs in the egg sac, which is held by the female in her chelicerae.
They have a potent, fast-acting poison enabling them to quickly immobilise prey item much larger than themselves.
Pholcus phalangioides is a very distinctive spider with its long legs. This one was found crawling over the wall in the Loire region of France. In the UK they tend to be found indoors or in cellars as far north as Dundee, although they do not thrive in centrally heated rooms, as the atmosphere is too dry. A fully grown adult has a body length of 8 - 10 mm, and a tubular abdomen. They feed on gnats and other small insects.
Mating and reproduction . There is little or no courtship before mating, and the male is not eaten afterwards. The mating can last as long as 3 hours. The males mature in spring and summer.
The mature female carries her eggs around with her in her jaws until the spiderlings hatch which is usually around 2 - 3 weeks after being laid. She doesn't make an egg sac, and the eggs are held together by just a few strands of silk. She will leave the eggs in her web so free up her chelicerae to capture prey, or even to mate again. The young may swarm over her head and cling to her fangs before dispersing in a week or two.
In the U. K. the first batch of eggs is usually laid in June, and there can be a 2 nd and 3rd batch at monthly intervals.
The web is very open and disorganised looking, and tends to be made high up, or in the corners of rooms.