The other evening I spotted a rather handsome spider making its way across the tiled wall behind the kitchen sink. It was one of the Tegenaria spiders, a group of several rather similar looking species and the bête noir of arachnophobes everywhere. These are the large ‘house’ spiders that you often encounter in the autumn as they run across the living room floor or become ‘trapped’ in a bath or sink.
Several of the species can only be reliably identified through careful scrutiny under a microscope and identification is additionally complicated by a degree of hybridisation between species, something that is rampant in some parts of the UK. This individual was a male, rather small in size and with the legs spanning just a couple of inches. Under a hand lens I could see the delicate legs, the subtle markings that chequer-boarded its abdomen and the modified palps, which form the male’s sexual organs.
This male was presumably wandering around looking for a female, the larger of the two sexes. Once he found a mate he would live with her for several weeks before eventually succumbing to old age. After death his body would feed the female and provide additional nourishment ahead of her producing a clutch of eggs. Female Tegenaria spiders are often overlooked because they spend most of their time within their webs. The silk used in these is not sticky; each web is long-lasting and may be used by a succession of spiders over time as the original occupants die and are replaced. Individual females may live for several years.
Although several Tegenaria species show a strong association with domestic and business properties they can also be found in other habitats, living amongst rocks, stones or fallen timber. The association with buildings is an interesting one. The conditions found in our homes do not necessarily lend themselves to spiders or other invertebrates, being dry and lacking in potential prey. Fortunately, house spiders can cope with the dry conditions and they can also go for long periods without sustenance. It is worth noting that they rarely bite and, apart from the webs that they make, you could say they make welcome and unobtrusive house guests.