Spider Notes

By John Partridge

On the Sunday following Recorders' Day, a few of us accompanied Garth Foster to Grimley Brickpits to do some water beetle hunting (see separate article for a species list). While catching water beetles, other species appeared, including one, small, immature male spider about 2 mm body length, with a shiny abdomen that I did not recognise. I took this home and kept it in a tube, hoping that its final moult was not too far off, and I would be able to identify it properly as an adult. For once this was successful, and the abdomen showed up as almost totally silvery, and the spider was identified as Theridiosoma gemmosum. I believe that this is a new county record for this Notable B species, but confirmation is awaited from Peter Merrett, who keeps these up to date.

Some of you may remember my requests for records for Pholcus phalangiodes, the daddy-longlegs spider, to see whether there was a North-South cut-off line for the species in the county. The records that I received as a result covered most of the county, but the new Atlas shows that this species can be found much further north, extending even into Scotland, so that line of research is now finished.

However, there is another spider that I would like you to keep an eye out for in the sunny days ahead, Misumena vatia. (No, even this largish and rather beautiful spider hasn't got a common name).

This pale female crab spider can be found in flower heads on sunny days, just sitting and waiting for insects to land before it grabs them for its next meal. Its coloration varies from white to pale yellow and pale green, with the mature females able to change the colour to match the background. For this reason, pictures of the spider in its natural habitat are not very clear, especially when reduced to black and white.

The new national atlas shows a very clear cut-off line for this species which goes straight through Worcestershire (map reproduced with permission), and our own county records, based on 2 km squares, show the same thing. It would be interesting to know how sharp this line is, whether it matches up with any natural features in the county, and whether it is moving. It is most likely to be found on umbellifer heads, or it could turn up in sweep nets for the habitual vegetation bashers amongst our recorders. Your records please to me, John Partridge via e-mail or any other route.