MIGRATION AND DISPERSAL OF INSECTS : LEPIDOPTERA. 101 



easterly direction. A friend of mine travelling from Kandy 

 to Kornegalle drove for nine miles through a cloud of white hutterflies 

 which were passing across the road by which he went." Mitford 

 writes {ZooL, 1895, p. 888) of the movements of ( 'atoji/iana iialnic in 

 Ceylon : " In the month of November, at Colombo, a strong north 

 wind blows daily along the seacoast, at which season clouds of white 

 butterflies appear Hying in a continual stream, extending far inland 

 for days and weeks. They are all flying from the south and in the eye of 

 the wind, and the stronger the wind blows the more rapid is their flight. 

 I never witnessed this fact without the greatest astonishment. 

 The locust, with its strong body and powerful wings, cannot make 

 head against the wind, but drifts with it ; yet that a butterfly with a 

 body so slight as scarcely to gain a fulcrum for the wings to bear on, 

 and with wings offering so broad a surface to the breeze that one 

 would expect to see it drift like a snowHake, should possess the faculty 

 of propulsion against a strong wind, gives us a clue to an aerostatic 

 principle with which we are not yet acquainted. It is to be noticed that 

 the action of the wings of these butterflies is not horizontal like that of 

 the Admiral or the Tortoiseshell, nor is their flight even and continuous, 

 but they are propelled in jerks, with the wings vertically closed and 

 opened alternately, so as to offer the sharpest edge to the 

 resistance of the wind. Thus the butterfly does not appear to propel 

 itself, but to be driven forward by the action of the wind eddying 

 round against the under surface of the wing presented to it, but how 

 this is done it is not easy to demonstrate. As there is no land south 

 of Ceylon, it seems evident that these butterflies deposit their eggs in 

 the southern forests of this island previous to their starting on their 

 migration, otherwise the annual flights could not be kept up. I 

 notice, however, that Mr. jNIann gives the months of March and 

 April as the season of migration witnessed by him ; but while he gives 

 the direction of their flight from north-east to south-west, he does not 

 state the direction of the wind. The 8.W. monsoon usually 

 commences in April, while the N.E. monsoon commences in October. 

 I assume that these are the same flights returning after a circuit of 

 the island, and flying against the southerly wind in the same manner 

 as those seen by me in NovemlDer were flying against the north wind. 

 1 cannot identify Navanghena, the place from whence ]\Ir. Mami 

 writes, and therefore do not speak confidently." Mitford's remark 

 as to the "return" of the insects is quite inexplicable. He surely 

 cannot think that the butterflies seen by thousands travelling from 

 the north-east in March are the same as those he saw in NoVcmbei- 

 flying from the south, and that the insects spend these six 

 months in a tour of the island. Aitken, the talented author of 'irihc>^ 

 nn Duj frontier, writes: "I have stood near one of the parade 

 grounds at Poona and watched them {(Jatoimlia) with scarce a pause 

 to rest their wings or sip a flower, from eight or nine o'clock until the 

 afternoon. As far as eye could reach the host kept streaming past, like 

 the fugitive (iauls after one of Caesar's great battles," whilst yet 

 another ol)server writes of CatopsiUa catilla : "In the flights along 

 the seacoast, beginning generally in November, two species of Catop- 

 silia form about a third of the number, always travelling to the north, 

 whilst the flights last foi- days, thousands of insects passing in an hour." 

 Another most interesting record, relating, however, to the Danaid group. 



