Cooke : On Scarcity and Abundance in Insect Life. 165 



moth, made its appearance, and is thus reported in the July number 

 of t}iQ E?domologists' Montlily Magazine'. — "They travel together in 

 thousands at a good speed, and devastate the land over which they 

 pass to an alarming extent. The inmates of a roadside inn are kept 

 continually at work brushing them out of the house. The road is 

 almost black with the larvae, whose advent is considered mysterious^ 

 numbers of people continually going to view them, and numbers of 

 larvae being exhibited in shop windows." 



Now, if we ask for a cause or explanation of these wonderful 

 phenomena, we are told that the season has been particularly favour- 

 able for the development of the larvse of Ckarceas graminis, or of 

 Tortrix viridana, as the case may be. Very true indeed, there cannot 

 be the slightest doubt about it ; but will this answer satisfy us ? If the 

 season has been particularly favourable for the development of the 

 larvae of (JliarcBah graminis, why has it not been particularly favourable 

 for the lurvse of a host of other species, which it must have affected, if 

 not precisely in the same degree, at least to a very considerable extent ? 



I have been taking some little notice of such larvae as have been 

 more than usually common during the past season, but my observations 

 have been confined to the immediate vicinity of Southport, so that I 

 should be glad to know what is the experience of others who have had 

 a wider range. The first in point of time was an unusual abundance 

 of the larvae of Acronycta megacephala ; they were to be seen almost 

 every day for several weeks on the walls of gardens wherever the Lom- 

 bardy or the black poplar grew. The next was the larvae of Smerinthus 

 populi, or poplar hawk, which appeared in greater numbers than usual. 

 There were also other poplar-feeding larvae, but taking all together 

 into account, the foliage of these trees was not very sensibly diminished 

 until the great storm which occurred about the middle of October. It 

 is said that in some localities the larvse of Bombyx rubi, or fox-moth, have 

 been very abundant ; I have not seen one myself, but towards the end 

 of October I noticed a great number of the larvae of Arctia fuliginosa^ 

 or ruby tiger. 



But there is another question to be asked about the larva of CJiaraas 

 graminis. It does not appear that any complaint of its excessive 

 abundance has come from any other part of the kingdom than the one 

 above mentioned ; how, then, does it happen that the season has been 

 particularly favourable for the development of the larva in excessive 

 numbers, not over the greater part of the northern counties of 

 England, nor even throughout the counties of Lancaster or York, but 

 solely in the neighbourhood of Clitheroe ? 



