August, 1915.} 225 



OBSERVATIONS ON SOME OP THE CAUSES DETERMINING THE 



SURVIVAL AND EXTINCTION OF INSECTS, 



WITH SPECIAL REFERENCE TO THE COLEOPTERA. 



BY GEO. B. WALSH, B.Sc. 



1. — Introductory. 



The larger part of my entomological experience has been gained 

 in the neighbourhood of the great industrial and commercial rivers of 

 North-eastern England — the Humber, the Tees, and the Wear and 

 Tyne — three districts which offer exceptional opportunities to the 

 student of certain branches of Entomology. Unfortunately for the 

 subject of this paper, there are no local lists of any age in either of 

 the Yorkshire districts. William Spence, the collaborator of Kirby 

 in the famous " Introduction to Entomology," has a number of Hull 

 records which are very useful, but the only attempts at compiling full 

 lists here are those made by various members of the Hull Field Club, 

 and these are quite modern. At Middlesbi'ough, owing to the very 

 recent origin of the town, there are no old lists, and there again the 

 local field club — the Cleveland Natural History Society — is doing 

 valuable work in compiling records which will be of great interest 

 when the town shall have much outgrown its present size. Durham 

 and Northumberland, however, rejoice in records of some age ; the 

 first part of Bold and Hardy's list of the Coleoptera of the two 

 counties, for example, dates back to 1848, and with this can be com- 

 pared the records made in recent years by Mr. E. S. Bagnall and the 

 present writer in the Newcastle area. 



II. — Geology, Surface, and Occupations. 



The Wear district falls naturally into the same division as that of 

 the Tyne. Then the three areas mentioned above differ very widely in 

 geology, surface features, occupations of the people, and character of 

 the insect fauna. 



(a.) The immediate neighbourhood of Hull and the whole of 

 Holderness are almost wholly boulder clay, with occasional glacial 

 sands and gravels; at no very distant date — certainly early in the. last 

 century — much of this plain was fenland, and even yet the enormous 

 number of artificial drainage ditches and streams forms a noticeable 

 feature of the countryside. Much of the la.nd touching the Humljer 

 is alluvium of quite recent origin, and five miles west of Hull there 

 commences the first uplift of the chalk of the Yorkshire Wolds. 



