1915.] 257 



OBSERVATIONS ON SOME OF THE CAUSES DETERMINING THE 



SURVIVAL AND EXTINCTION OF INSECTS, 



WITH SPECIAL REFERENCE TO THE COLEOPTEBA. 



BY GEO. B. WALSH, B.Sc. 



{Concluded from 'page 232). 



V. The Ttne and Wear Area. 



This district differs from the other two that I have mentioned in 

 that it possesses local lists of Coleoptera, Hemiptera, etc., which are of 

 some age, but unfortunately the industrialism of the two counties dates 

 back to so remote a pei'iod (coal is said to have been first worked near 

 Newcastle about 1300 a.d.) that it is pi'obable they represent a state of 

 affairs not widely different from those existing at the present time, 

 except in the extent of land built on. In the part between New- 

 castle and Gi-ateshead and the sea the riverside is flanked by town after 

 town, with a semi-rural area behind them also thickly dotted with 

 villages, largely in connection with collieries, and cut up in all 

 directions by roads. The country is largely low fell land, covered with 

 rough grass and mainly under pasture. Probably at no time have 

 there been many trees on the fells, though the numerous valleys cut by 

 the streams through the overlying clay were at one time thickly wooded 

 with willows, alders, birches, etc., and even now contain the best- 

 timbered parts of the district. A number of years ago the chemical 

 industry was much more important on Tyneside than it is to-day, more 

 particularly near Jar row, and, before the adoption of more scientific 

 methods of working, great quantities of injurious gases, especially of 

 hydrogen chloride and chlorine, were allowed to escape into the air. 

 These must have done great damage both to vegetation and to animal 

 life, especially in the neighbourhood of this town- — indeed, local tradition 

 of no very great age asserts that the cattle died in the fields through 

 eating the poisoned herbage. The objectionable chemical works have 

 now, however, almost all vanished, and except for occasional faint 

 chloi'ine smells, injurious fumes are a thing of the past. Consequently, 

 fields are once more clothed with herbage, and insect life is common. 

 Still, there is no doubt that when the nuisance was at its worst, insects 

 must have suffered as did the higher forms of life ; but since that time 

 there has probably been a certain amount of repopulation, so that now 

 phytophagous insects of common species can be found quite close to 

 Jarrow, e.g., Hadena insi L., Riitnia crataegata L., Hepiahis lupulinus 

 L. ; Paraphaedon tumidulus Grerm., Fhyllohius jpomonae 01., Apion 



