Southern Marsh Orchids

Southern Marsh Orchids

Thursday, 2 January 2014

Tegenaria agrestis

Whilst out on the obligatory Boxing Day stroll I spotted a spider from the Tegenaria family that was lurking under a stone in a nearby abandoned quarry.  There are about 10 species of Tegenaria found in Britain, and they include the big scary hairy House Spiders that seem very fond of arachnophobes in the autumn when they move indoors to escape the inclement weather.  They are quite distinctive looking as a groups, but like many spiders are impossible to separate on the basis of pattern or colour.  It is necessary to look at the male palps or the female epigyne under a microscope.

This one was not one of the commoner species such as the familiar House Spider, but Tegenaria agrestis.

It was first recorded in Britain in 1949 and prefers disturbed brownfield habitats.  It is a widespread European species and has a wide but patchy distribution across  much of England but there are comparatively few records from Wales.  Glamorgan records are restricted to a couple of sites to the West of VC41.  It is thought to spread along railway lines, using the track-side ballast as an ideal habitat.  Sure enough, the abandoned quarry south of Rhoose village is less than a hundred metres from the Aberdare to Bridgend line that services Aberthaw power station.  It is quite likely to be present in other areas of suitable habitat along the railway corridor I guess.

Tegenaria agrestis distribution
Source: Spider Recording Scheme/British Arachnological Society (2012) Website and on-line database facility


  1. About how large would one of those be?

  2. They are reasonably large Mark, with the females (according to the book) having a body length of 10 to 15mm. The reference specimen that I have kept could actually be slightly longer than 15mm but it is hard to tell as it is a bit curled up in the tube. There are larger Tegenaria's out there, but T agrestis are mid to upper size range for the Genus. Like the ones you find in the house in the autumn, the males have much longer legs but smaller bodies than the females.

    The adult size of spiders varies quite dramatically, presumably in large part due to their nutritional status as juveniles. The warm summer we've just had may have helped them reach their upper size limits for some species perhaps in 2013.