Summary for Porrhomma egeria (Araneae)
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About this speciesRecorded altitude range
30m to 640m
The species has a widespread but very scattered distribution in Britain. It is fairly widespread in north-western and central Europe, but has not been recorded from Denmark, Norway or Hungary.
Habitat and ecology
This spider said to be predominately a cavernicolous species, often exploiting the deeper parts of the cave system (e.g. Ružicka 1996). Outside of the cave habitat, P. egeria has been found down mines, amongst stony debris within moss and occasionally in cellars. However in Britain recorded habitats are varied, with the spider probably occurring in smaller cavities within these. Gradual eye reduction has been observed in this species which is dependent on the distance from the cave entrance (Sanocka (1982), cited in Ružicka (1996)). Never occurring in any numbers, its ecology and phenology still remain something of a mystery, although it is known to use a web for prey capture and has been recorded in several months between February and September.
The species has been recorded from ten locations since 1992. Although its specialised habitat may have resulted in some under-recording, this species appears to have suffered a significant long-term decline of 70%.
Some cave systems in which it occurs may be threatened by quarrying.
Management and conservation
Although more information on this species' micro-habitat requirements and ecology in Britain is needed, destruction or disturbance of caves or abandoned mines where it occurs should be strictly avoided.
Text based on Dawson, I.K., Harvey, P.R., Merrett, P. & Russell-Smith, A.R. (in prep.). References