Encounter with a spitting spider

As soon as I saw her I was pretty sure of her identity; Scytodes thoracica, the spitting spider. Once she was safely sealed in the confines of one of my specimen tubes I checked her identity against a guide and took in her spiderly beauty. Very pale brown in colour, Scytodes is delicately marked with a deeper brown through a succession of spots on her thorax and strongly domed carapace, and bands on her thin legs.

The large, domed carapace is a striking feature and houses a pair of enormous double-lobed glands. The front lobe of each produces poison while the larger rear lobe produces a sticky, glue-like substance. Each gland is linked by a duct to the front of the fang where it emerges through a small opening. By using muscular contractions to compress the gland, the spider is able to ‘fire’ a stream of poisonous glue at its intended victim, easily covering a distance of 10mm or more. At the same time, the spider very rapidly moves its fangs from side to side, creating a zig-zag of deadly spray that quickly immobilises its prey; only then does the spider approach more closely and deliver the coup de grace. If there is any sign of a struggle on the part of the victim, Scytodes will deliver the bite to one of the extremities before retreating and playing her patient game.

As its weaponry might suggest, this is an active hunter which does not bother to build a web, but instead stalks prey with a slow and steady gait. Scytodes is synanthropic in habits, which means that she lives alongside us in our houses and offices. Although widely distributed within southern Britain, south of a line from the Humber to Glamorgan, this spider is either somewhat uncommon or poorly reported. I have only seen her twice in the 10 years that I have lived in this old house and I do not recall seeing her in any of the other houses in which I have lived. This house is quite old and seems to support a good number of spider species. The spider’s powers of dispersal may be rather poor, since it’s young do not disperse on the breeze, so dispersal is likely to be through the movement of household objects from one location to another. Another factor that may restrict the species to low levels of abundance is the length of time (some three years) that it takes the females to reach maturity. We tend to think of insects, spiders and other invertebrates as being short-lived, ephemeral creatures but this is not always the case. Having secured her identity I released her, in the hope that she remains unnoticed by my wife!