Chaotic picks?

Insecta:

Click here to listen (also download is possible by registering):
http://yourlisten.com/channel/content/16950631/Chaotic_picks?

This recording was made with the help of the microphone of a digital camera, which only registers below 8kHz. On the other hand I had a Bat Detector device, tuned at 20kHz, which was switched on at 1.6" (before it, it was "silence"), so the "output sound" of the Bad Detector device could then be heard and recorded.

There are two kinds of sounds; the first brings to mind the sound of dozens of workers with picks in a mine; the second is similar to the sound of scratching a match in a match-box. Unfortunately both them are in the same freqüency spectra and can't be isolated, although it could be that they were produced by the same animal species. It seems there were some individuals, so any possible common pattern is difficult to be shown up; in fact it could be a gregarious species.

I suggest it could be ants (Formicidae) or termites (Dictyoptera: Isoptera).

It was recorded near a countryside house. The sound was louder as I focused the trunk of a Celtis australis tree, covered by ivy Hedera helix, but it also could came from the ground or the branches.
The next morning I found in a branch a Theridiidae spider, Rhomphaea rostrata.

Recorded the 5th October 2008, 00:24 am, 9ºC, in a "gardened" place in a stone oak Quercus ilex forest margin.
[Iberian peninsula: Catalonia: Girona province: Garrotxa: Beuda: Can Grau][GoogleMaps]