The dominant group of Coleoptera (beetles) were carabides of the 

 species Pterost ichus niger followed by Hydrophilidae of the genus Cercyon, 

 common in decaying wrack on shores (Chinery, 1976). These occurred only 

 at Stations C and G, where the humidity was high, since they feed on 

 even wetter wrack than Orchestia (Backlund, 1945). The family Ptilidae 

 was also frequently found, some species of which are very common in 

 wrack beds (Backlund, 1945). Staphylinides , of which many species live 

 on shores and feed on Diptera larvae, also occurred in the samples as 

 well as Nitidulidae, which lives on decaying material (Chinery, 1976). 



In all calculations the newly hatched individuals of Porcellio and 

 Orchestia were omitted. At station B there were 81 newly hatched Porcellio 

 (among 19 adults) still clinging to the mother adult in one trap, and in 

 one quantitative sample there were 75 newly hatched individuals of the 

 same species among 6 adults at the same station. If these had been 

 taken into account, the average number of individuals in each trap would 

 have increased to 27 (instead of 20), just a little less than at the 

 other stations and the average number of individuals per 100 g wrai k 

 would then become not 85 but 158. This would make the figure comparable 

 to that at station G. In fact, fur the small amount of material examined 

 the differences in number of individuals and systematic groups between 

 the stations are not so large that they could not be explained by the 

 natural variation caused by the environment. The wrack bed is a rela- 

 tively variable environment, strongly affected by storms. Nevertheless 

 it was of a similar nature throughout the whole area investigated during 

 the sampling period, so that a comparison could be made between the 

 s t iti'-ns. 



The humidity is a factor of great importance to the animals living 

 in the wrack itself (Backlund, 1945). Water makes the wrack much softer 

 and mure accessible and therefore easier to eat. Orchestia for example 

 cannot eat hard and dry wrack (Backlund, 1945). Another important 

 factor influencing the wrack fauna are the interactions over the "bound- 

 aries" to adjacent biotopes (Backlund, 1945). At station G for example 

 tin bed of reed comprises another biotope containing other types of 

 animals supplying immigrants to thi rick fauna. Thus the surrounding 

 biotopes influence wrack beds both quantitatively and qualitatively. 



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