Agelenidae: funnel weaver spiders

The agelenidae comprises 11 species in three genera, the best known, Tegenaria, or house spiders, includes several species difficult to identify without microscopic examination, and some that hybridise, further complicating identification. They weave sheet webs ending in a funnel. The spiders of this family, in particular house spiders appear to elicit fear or disgust in many people. Even William Bristowe, passionate arachnologist, confessed his 'horror' of the house spiders. The male's habit of rapidly running across the floor in the night, or appearing in the bath in the morning doesn't gain them any friends. Their amazingly long, hairy legs and large size doesn't make them endearing either. 

Males on the prowl

Tegenaria males mature in summer and autumn at two years of age and it is at this time of the year that them, which would have been living unobtrusively, in the corner of a room or behind a counter in the kitchen, leave their webs in search of females. They are most likely to be encountered then, either running across the floor a night or, in the morning, having fell into a bath from which they cannot escape. When a male meets an immature female he will stay on her web, waiting for her to mature and eventually mating with her. She accepts the male in her web and after more mating, the male will die.

A male Tegenaria sp. in the bath.

A Tegenaria moving across the floor.

Maternal spider

Female Tegenaria will lay several batches of eggs in spring in eggs sacs decorated with soil, debris or remains of prey. The spiderlings remain on their mothers web for a few weeks until ready to disperse. Read more about this topic in this post at Bugblog.

A female Tegenaria by her sheet web.

Tegenaria on her sheet web on ivy. I enticed her out of her retreat with some water spray.

A male Tegenaria, probably a T. gigantea x saeva hybrid. Males are slimmer and have longer legs than females. The modified male palps, used during mating, are visible in this photo and in the top photo of the same male.

Bath spider hybridization

Since the end of July, large spiders with long legs have been running across carpets in the house, or falling in the bath. Being agile spiders that often react to disturbance by jumping and running very fast - as opposed to crouching or playing dead - these are spiders that tend to scare people. They are males of several species of the genus Tegenaria. This guy fell in my bath a couple of nights ago and it has been the most compliant Tegenaria I've had so far. He sat still on the white bowl while I got close to its palps, but despite getting good views, I still was unable to ID it.

The two most common species in the UK are Tegenaria gigantea (=duellica) and T. saeva, and this male's palps could have been either. These closely related species differ in details of the female genitalia and of the morphology of the male palps, but their recent history is blurring the distinction between them in the north of England. Work by Peter Croucher, Geoff Oxford and colleagues from the University of York show that both spider species expanded north after the glaciations from refugia in the Iberian Peninsula. Through the vagaries of the colonisation process until recently, they had a mainly segregated distribution in the UK, with T. gigantea in the east of the country and T. saeva in the west.

Distribution in England and Wales of Tegenaria saeva and T. gigantea based on 10x10 km grid squares of standard maps (Ordnance Survey, the national mapping agency of Great Britain). Black squares, T. saeva; white squares, T. gigantea; grey squares, those containing both species. Spiders with intermediate morphologies are not included (figure from Croucher et al 2007).

In the south of the country, both species distributions meet in a narrow stable zone, in Dorset, where hybridisation appears not to be very common and when it happens results in high hybrid mortality. Since the 1970s, however, both species have expanded into Yorkshire and in this region they often occur in the same places and hybridise commonly, so that their species boundaries are falling apart and many morphologically intermediate forms are found. As Hull is in an area of high hybridisation, my inability to ID the spider might have more to do with my limitations, but there is a high chance there is no "pure" T. gigantea and T. saeva in this area any more, and that these house spiders are actually merging into one as they carry on colonising towards the north.

More information
Croucher, P., Oxford, G., & Searle, J. (2004). Mitochondrial differentiation, introgression and phylogeny of species in the Tegenaria atrica group (Araneae: Agelenidae) Biological Journal of the Linnean Society, 81 (1), 79-89 DOI: 10.1111/j.1095-8312.2004.00280.x
Croucher, P., Jones, R., Searle, J., & Oxford, G. (2007). CONTRASTING PATTERNS OF HYBRIDIZATION IN LARGE HOUSE SPIDERS (TEGENARIA ATRICA GROUP, AGELENIDAE) Evolution, 61 (7), 1622-1640 DOI: 10.1111/j.1558-5646.2007.00146.x