MIMICRY 221 



were "fairly jostling" each other; but the air seemed 

 to be full of them as far as the eye could see, and 

 by standing on an open lawn I was able with one 

 sweep of a net to catch half a dozen. I can never 

 hope to see such a remarkable sight again. Identi- 

 cally the same phenomenon occurred at Sadong, a 

 place thirty to forty miles north-east of Kuching, and 

 I am sure that the swarm was continuous over this 

 great tract of country, and probably beyond it. A 

 friend residing on Mt. Matang, seven miles due west 

 of Kuching, reported that the butterflies arrived there 

 at about 4 p.m. Next day, at the same hour, the phe- 

 nomenon was repeated, though on a much smaller 

 scale [Note 17, p. 316], It is exceedingly difficult to 

 account for the sudden appearance of these vast 

 hordes. Cirrochroa bajadeta is normally a fairly abund- 

 ant species, though not extremely common, and I could 

 gather no evidence whatsoever that the species pre- 

 paratory to the great flight had been more abundant 

 than usual. We can only suppose that most, if not all, 

 the factors which normally held in check the increase 

 of the species had been at some time temporarily sus- 

 pended, and we can realize faintly what would happen 

 if there were no such thing as a struggle for life. Even 

 granting this, it is difficult to account for the syn- 

 chronous appearance of these hordes, whilst the object 

 of their migratory flight is equally buried in obscurity. 

 But it is evident that a vast multiplication of numbers 

 must affect the future history of a species very con- 

 siderably, and a species once rare in a given locality 

 may, by the accession of large numbers, become quite 

 common, at any rate for a period of time. 



Just as it is absurd to suppose that all obscurely 



