336 THE ZOOLOGIST. 



looked out specimens for comparison in the British Museum 

 Collection, it was soon apparent that the insects captured by 

 Mr. Mann were males and females of an Asiatic black and white 

 butterfly tolerably well known to entomologists as Catophaga 

 galena, Felder, having a general resemblance, both in size and 

 colour, to our Cabbage Butterfly, and not unlike C. lankapara, 

 Moore, excepting on the under surface, which is less yellow in 

 the male, and pearly in the female instead of orange. 



Phenomena such as that witnessed by Mr. Mann are not unre- 

 corded, although little or no attempt has been made at explanation. 

 Sir J. Emerson Tennent, in his ' Natural History of Ceylon,' 

 says : — " At times the extraordinary sight presents itself of flights 

 of these delicate creatures, generally of a white or pale yellow hue, 

 apparently miles in breadth, and of such prodigious extension as to 

 occupy hours, and even days, uninterruptedly in their passage — 

 whence coming no one knows ; whither going no one can tell." 

 He adds in a foot-note : — " The butterflies I have seen in these 

 wonderful migrations in Ceylon were mostly Callidryas hilarice, 

 C. alcmeone, and C. pyranthe, with straggling individuals of the 

 genus Euplcea, E. coras and E.prothoe. Their passage took place 

 in April and May, generally in a north-easterly direction. A friend 

 of mine travelling from Kandy to Kornegalle drove for nine miles 

 through a cloud of white butterflies which were passing across 

 the road by which he went." 



In this observation, and in the case mentioned by Mr. Mann, 

 it will be noted, first, that the species recognised were not identical 

 (although not distantly related), and, secondly, that the insects 

 were travelling in precisely opposite directions, a circumstance 

 which suggests that the direction of their flight may in some 

 measure depend either on the prevailing wind at the time of the 

 occurrence, or upon certain atmospheric conditions such as 

 influence the migrations of birds. 



Nor is it in Ceylon only that this phenomenon has been ob- 

 served. In South America something of the kind was witnessed 

 by Darwin, who has thus graphically recorded the observation in 

 his ' Naturalist's Voyage in the Beagle' : — 



" Several times when the ship has been some miles off the 

 mouth of the Plata, and at other times when off the shores of 

 Northern Patagonia, we have been surrounded by insects. One 

 evening when we were about ten miles from the Bay of San Bias, 



