1; 
All entomologists will tell you that butterflies have become 
very much rarer within living memory. The pride of English 
entomologists, the glorious Large Copper found only in the 
English Fens, disappeared sixty years ago quite suddenly. Several 
other species seem extinct; and in general all kinds, excepting 
the mischievous Cabbage Whites, are far less abundant than 
formerly. The explanation seems obvious, that too many entomo- 
logists of all ages continually attack them; while the modern 
facility of locomotion—a facility considerably enhanced during 
the past generation—continually narrows retreats of undisturbed 
retirement where nature is independent of man. Yet what I am 
about to tell you will throw a different light upon the subject, and 
you will see that other causes are in operation. 
The first consideration, though not the most important, is 
Dame Nature’s trick of producing during one particular year a 
more or less rare species in countless profusion. The beautiful 
and swift Clouded Yellow butterfly thus appeared in 1865, 1877, 
1892, and rgoo. In the preceding and following seasons it was a 
rarity. Still more prized is the Pale Clouded Yellow, swifter though 
less beautiful than its relative, and generally very rare. In 1868 it 
was extremely common, never subsequently, Why should this 
be? That year was very hot and dry ; but the butterflies must 
originally have been eggs laid by females, and however favourable 
the weather, the problem remains. When and where did the 
females lay the eggs that inexplicably produced countless butter- 
flies of a species extremely rare in other years? 
Why, too, did not the ordinary Clouded Yellow, whose life 
story is practically the same, also appear in its multitudes in 1868, 
as it had done years earlier? These questions still remain for 
solution. Again, in 187z, when I was the Society’s youngest 
member, I announced the capture of a Camberwell Beauty ; and 
was informed they were fairly common that year. Ever since 
they have been extremely rare. 
More profound is the subject I next touch upon. Our South 
Downs are peculiarly suitable to blue butterflies, whose caterpillars 
feed on plants common here. But the Large Blue (Lyceena 
Arion) is not found here, or in all this part of England. And 
its life history has been quite unknown till just lately. 
The Large Blue has always been a valued prize among 
English butterflies ; though usually very common where it occurs, 
it favours slippery and dangerous places, such as old quarries and 
rocky pastures, and in a few counties only. The localities 
formerly known were Barnwell \Wold in Northamptonshire, and 
three places in the Cotswolds; afterwards South Devon and 
Cornwall. From all parts of England entomologists used to visit 
Barnwell Wold ; and sure enough the Large Blue was killed off 
there. It also disappeared from the Cotswolds and Devonshire, 
