Tuesday, 31 March 2015

Tenuiphantes cristatus

This little spider was another picked up by shaking grass cuttings at the weekend. I feel like I'm starting to get my eye in on the Linyphiid spiders, and to get to grips with the key tables. Now I know what I need to record before I open the book.

'Formula' for this spider is:  2-2-2-2, TmIV absent, TmI @ 0.15

This means that the dorsal spines on the tibiae are 2 on tibia 1, 2 on tibia 2 etc., there is no trichobothrium on metatarsus IV, and the trichobothrium on metatarsus I is at 15% of the distance from the proximal end.

The trichobothrium is a little sensory hair which has a pit at its base. Sometimes the pit is easier to locate first, but sometimes the hair is easier to locate because it vibrates when there is movement - a subtle move of your chair, a cough - anything. It is VERY sensitive. Trichobothria can sense air movements of prey items (flies) when in close proximity (link). This makes it harder to photograph, because essentially it's always moving. The pit is located in between the lines of other hairs on the leg - see picture 3

There is another Linyphiid rule I forgot. Must be broken sometime but the rule is as follows: "Where a number of species have size ranges your spider will be the exact size that meets the requirement for all candidate species!"

A very similar rule applies to fungal spores.

Spiny chelicerae

Why don't palp drawings also have this view?

Dark trichobothrium pit slightly right of the spine


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