Study 2

Fen Raft Spider behavioural study record 002


Location:  Carlton Marshes: Dyke 10, immediately by northernmost red and white verge marker post

Date:                                                  08.07.19

Time start:                                        14.00

Time finish:                                      16.10

Weather (from BBC weather app):

  • General:                Mild day, breezy
  • Humidity:              –
  • Pressure:                –
  • Temp:                     17.5C
  • Temp feels like:     –
  • Wind:                      Moderate breeze
  • Cloud cover/sun:   Intermittent cloud, mostly sunny


Nursery web with spiderlings. No adult seen.

Vegetation/macro location:

Web in sedge, about 12 inches above water, in margin.


The web in study 01 can no longer be seen. This web is further south along the same dyke.

14.00. Spiderlings in a torus formation, the right-hand half shaded, the left in sunlight. Bursts of activity noted in two forms: one as a cascade spreading over the surface of the huddle of spiderlings, the other as a simultaneous burst of activity all over the surface, with individuals at separate points around the huddle simultaneously starting movement. Does this suggest different stimuli for activity? There was no visible trigger for the activity, which always settled down within a few seconds.

14.45. Longer spells of sunlight on web and increased frequency of bursts of activity noted during this period.

14.50. Several bursts of activity occurring within the space of one minute but lasting only a few seconds. These bursts were in the simultaneous pattern.

15.00. It is possible to see now from a different viewpoint that the torus is in fact two separate balls of spiderlings. Learning point: get several viewpoints where possible.

15.30. There are in fact three balls of spiderlings, with one to the left of the others, shaded and well hidden under a broad sedge leaf. The other two are now both unshaded and bursts of activity are noted in both, when the sun emerges. The balls are beginning to join up.

15.55. Sunlight now continuous as clouds have broken up. The two right hand balls have coalesced to form a crescent concave upwards, approximately facing the direction of the sunlight. More a radio telescope shape than a lens shape.

Observed formation shape change consistent with basking behaviour to increase body temperature. This would increase metabolic rate and consequently growth rate.

Increased activity during periods of sunlight consistent with increased metabolic rate and muscular activity with increased body temperature.

Stimuli for activity bursts not known.

16.10 End.


The hidden third noted ball of spiderlings on the left, shaded by a sedge leaf. The next two are visible and partly obscured.


Same view closer in and a little later.


Crescent formation

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