OCCASIONAL ABUNDANCE OF INSECTS. 37 
sufficiently so at any rate for the purpose. One word as to 
the entomological records,—Deilephila galw is a fortunate 
subject for investigation because its occurrences have 
almost always been recorded in the entomological serials 
and they may be taken without hesitation, as this is a 
species no one could mistake for any other. 
In 1834 we hear of the species at Yarmouth, Isle of 
Wight, Peterborough, and in Somerset. Then a few 
single specimens from 1835 to 1847 not one from 1847 to 
1853 then only two or three records till 1859 when we hear 
of seventy taken at once on the south coast, forty or fifty 
at Deal, many at Wallasey, also at Perth, Darlington, 
Cambridge, Taunton and in Dorset. 
After that year two in 1860 and then only three between 
1860 and 1869. Then in 1870 we have larve taken in 
hundreds north, south, east and west, Deal, Lancashire, 
Cheshire, Fifeshire, Northumberland, Sussex, Suffolk, 
Derby, Herefordshire, and Gloucestershire. In 1871 
eighteen larve all told then none till 1876, two in that year 
then only one till 1888 twelve years. 
In that year nearly every entomologist filled up his 
series, they were everywhere where they had ever been. 
Now I want to point out before proceeding that nearly 
all these records refer to the larve. Probably not fifty 
imagines of Deilephila gal have ever been taken in 
Great Britain. The years of abundance mean years of 
larval abundance. Therefore I believe that it is during 
the year previous to the summers when the larve are so 
abundant that we must look for the critical time, the time 
when some atmospheric condition allowed a survival so 
very much greater than usual and that the numbers of 
larvee which we saw say in September, 1888, were really 
due to influences at work in 1887 and not materially neu- 
tralized in 1888. On this assumption I have arranged 
