OCCASIONAL ABUNDANCE OF INSECTS. 43 
during every moment of being. I believe it to be with 
Deilephila galvi one of the most important but only one 
among a multitude too delicate to guage and too subtle to 
detect. 
To those entomologists who love to cut the Gordian 
knot of biological difficulties with the ready sword of 
some heroic but unsupported theory, and who call gali, 
as the Welsh prince called spirits from the vasty deep, 
such a conclusion, namely that these abnormal years of 
abundance may be due principally to nothing more start- 
ling than a dry autumn, may seem lame and impotent 
enough. Whether indeed there may be any other influence 
at work whose operation I have overlooked, whether there 
be anything in heaven or earth as touching the economy of 
Deilephila galw undreamt of in our philosophy I am in 
no position dogmatically to say. I simply submit these 
investigations and the results I have attempted to deduce 
from them in the hope that they may to some slight 
degree help to clear the obscurity, or put on a more 
rational basis the theories, which have hitherto involved 
the consideration of the most conspicous and best known 
instance of this singular phenomenon of the intermittent 
ebb and flow of racial vitality. 
