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to arrive on this side of the water, either in spring or summer, 

 large enough to account for the unusual numbers seen this year. 

 But, assuming that from some cause these insects are un- 

 usually abundant on the opposite coasts, so as to be able to 

 migrate in numbers to this country, might not the same 

 causes which favour their abundance there apply equally on 

 this side, without the intervention of migration ? Probably 

 under ordinary conditions considerably less than lo per cent, 

 of the ova deposited by the parent produce imagines, their 

 enemies are so numerous that it almost seems wonderful 

 that any escape. But let us suppose that by a combination 

 of circumstances some of these enemies are held in check for 

 a season. Should we not then have an unusual abundance ? 

 It appears to me that such a state of things is by no means 

 impossible, and that the question is one well worthy of further 

 impartial investigation. 



" Among the other butterflies noted were Satyrus semele^ 

 L., and Epinephele ianira, L., both very common, many of 

 the latter being considerably under the average size ; E. 

 tithonus, L., Pararge megcEra, L., C(znonynipha pamphilus, L., 

 Polyovimatus pklcsas, L., Lyccsna icarus, Rott., L. bellar- 

 giis, Rott., and L. corydon, Fb., all in considerable numbers, 

 together with a few Argynnis aglaia, L. With regard to L. 

 corydon and bellargiis some diversity of opinion appears to have 

 existed as to whether these two species were usually to be found 

 flying freely together, and I was certainly under the impression 

 that the former was almost, if not quite, over before the latter 

 began to appear at any particular place ; but my observations 

 this summer lead me to quite the opposite conclusion. On 

 my first visit to the Downs (August 1st), corydon was flying 

 very commonly; and on each successive visit, up to the 2ist, a 

 similar state of things was noted. On that day a male was 

 taken just emerged from pupa, but up to this time no bellargits 

 had been seen. On the 28th another freshly emerged male 

 corydon was observed, and both sexes were flying abundantly, 

 many of each being in perfect condition. On this day I 

 saw my first bellargns (2 $'). On September 2nd a heavy 

 storm swept the coast, and broken weather continued for 



