124 



been equally marked all over England. As an instance of the 

 profusion in which this insect has occurred in the Midland coun- 

 ties, it may be stated that the writer took upwards of thirty pupae 

 of it from a carrot bed only a few feet in extent and after a very 

 superficial search. The imagoes emerging from all of them within 

 a few days of one another. 



We know, however, far too little of the lives of insects to 

 draw any conclusions from their emigrations. But the absence 

 of many species from England which are common on the conti- 

 nent in localities at its nearest points to the latter is significant, 

 and points to the fact that migration in bulk rarely, if ever, takes 

 place. 



There is another well known species of insect which has 

 occurred in great profusion throughout England at irregular 

 and usually widely separated periods, viz., the clouded Yellow 

 Butterfly (Colias edusa). 



In the year 1876 a few occurred in certain localities in the 

 Midlands, as well as in other parts, late in the summer ; but in 

 the following year, 1877, the species simply swarmed. Now of 

 the very numerous examples captured by the writer and his 

 friends, not one exhibited any signs of having undertaken a long 

 journey. All on the contrary had the appearance of having 

 newly emerged from the chrysalis. There can, therefore, be no 

 question that the larvae had been hatched locally and that the 

 great abundance of the species was due to the prevalence of 

 certain favourable conditions of the nature of which we are quite 

 ignorant. 



The abundance of Plusia gamma, which, however, is at all 

 times a common insect, may, no doubt, be attributed to a similar 

 cause. 



Of the other species mentioned by Herr Gatke, certain of them 

 are such feeble and lethargic flyers that a journey to any distance 

 beyond the island is simply an impossibility. 



It will be noted that on one occasion, viz., August 19th, 1882, 

 a strong migration of birds took place accompanied by thousands 

 of Plusia gamma. " A thunderstorm with high winds, subse- 

 quently put an end to the migration " and no doubt put an end 

 to the individuals comprising the flights of Plusia gamma at the 

 same time. 



