224 



THE SPIDERS OF THE MIDDLESBROUGH 

 DISTRICT. 



Bv J. W. H. Harrison, B.Sc. 



The above title in general terms describes the district 

 that has produced the Spiders included in the following 

 catalogue. Nevertheless, certain species have been included 

 which have occurred on the Durham Coast, because these 

 Durham localities have been worked previously by the 

 Field Club for other groups. 



An examination of the list will betray the fact that the 

 bulk of the species belong to the Theridiids (sens, lat.) 

 Several reasons may be given for this fact. First, the 

 Theridiidae and Argiopidae are by far the most extensive 

 of the families represented in Britain. Again, as no collect- 

 ing was done for nine weeks in summer, other families which 

 mature during the summer months to a greater extent than 

 the Theridiids do, have thus escaped observation in the 

 adult condition. Probably, too, the sub-alpine character 

 of the chief localities worked has further extended the list 

 of this family. 



The district is apparently a very rich one in Arachnids, 

 and two species have been discovered new to Britain. One 

 of these, Hypselistes florens, provides the first European 

 record. The other has been recorded previously from 

 France. Besides these, there are several species new to 

 Yorkshire. These, amongst others, include Erigone arctica, 

 Troxochrus scabriculus and Cnephalocotes interjectus. Other 

 records extend the range of very rare and little known forms. 

 Particularly worthy of notice in this group are Caledonia 

 evansii, Evansia merens, Leptyphantes nebulosus and Porr- 

 homma miserum. 



In all, a little more than five months' collecting has 

 produced these species. Investigations made further afield 

 in localities of a more varied nature will considerably 

 extend this list. 



