Amaurobius similis  (AMAUROBIIDAE)

Amaurobius similis

This spider lives in holes in walls or under tree bark during the day. At night the males go wandering, while the females partially emerge from their hiding places. The females spin a very fine web of silk around the outside of their hiding place that is designed to trap their prey. This silk is spun from a special area of the spinnerets, known as the cribellum. The spider will tease out this silk using a comb on its hind legs, called the calamistrum.
The photo is of a male Amaurobius similis, taken at night as it seeks out a mate. Note the dragline at the rear of its abdomen, which permits it to retrace its steps without relying on its poor eyesight.

Head and chelicerae of Amaurobius similis The bottom end of the chelicerae of Amaurobius similis, viewed from the side nearest the mouthparts. Left Pedipalp (male sexual organ) of Amaurobius similis

Epigyne (female sexual organ) of Amaurobius similis Another micrograph of the Epigyne (female sexual organ) of Amaurobius similis, with fewer hairs A close-up dorsal view the palpal tibia of a male Amaurobius similis. This is a very useful aid to distinguishing between the individual species of Amaurobiidae.

Spinnerets of Amaurobius similis. Cribellum of a female Amaurobius similis (arrowed) The two halves of the cribellum of Amaurobius similis (arrowed)

Detail of the cribellum of Amaurobius similis showing the individual nozzles. The outside diameter of the stalks is approximately 500 nm, measured about half way up. An artificially coloured version of the micrograph of the cribellum of Amaurobius similis to the left. Calamistrum (on meta-tarsus IV) of Amaurobius similis (arrowed)