17& h. de Niceville — List of the Butterflies of Geylcm, [N^o, 3, 



is occupied by Puttalam, Mannar, Jaffna, Tangalk and Hambantota. 

 We should like to make a remark with reference to the two dry zones 

 of the Island mentioned above, which represent the largest portion of 

 the Island. At one time they were the most populous and prosperous, 

 but now the most sparsely populated and most unhealthy districts of 

 the Island. The ruiti of these districts is due entirely to the fact that 

 the rainfall is not now stored for the purposes of cultivation as was 

 done in ancient time." 



The seasons are very well marked, and consequently those genera 

 such as Terias which are subject to seasonal variation show these 

 modifications very distinctly. The dry-season begins about the end of 

 January, and lasts with an occasional shower until the burst of the 

 South-West monsoon in the beginning of June. As soon as this is 

 established butterfly life becomes abundant, but gradually diminishes as 

 the monsoon dies away. In September there is usually a spasmodic 

 revival just before the setting in of the North-East monsoon in the 

 middle of October. After the initial heavy rains, butterflies start afresh 

 in November, December and January, and it is in these months more 

 especially, though to a slighter extent at the beginning of the South- 

 West monsoon, that the extraordinary migratory flights of butterflies 

 take place. These flights are perfectly amazing and scarcely credible. 

 At Colombo, where Manders has more particularly noticed them, the 

 direction of the flight is always northerly and principally along the 

 seashore, possibly the more readily to avoid obstacles. The species 

 which comprise these sensational flights are the following to the ex- 

 clusion of almost any other: — Euploea asela, Moore (and E. montana^ 

 Felder, at Nuwara Eliya in May), Appias alhina, Boisduval, and Appias 

 paulina, Cramer, the two Catopsilias, Papilio demoleiis, Linnaeus, and 

 Belenois mesentina, Cramer, irregularly. He calculated the number pass- 

 ing two fixed points 20 yards apart close to the edge of the sea, and con- 

 cluded that not less than 14,000 passed between these points during the 

 hours the flight lasted from 10 a.m. to 2 or 3 p.m. There is no doubt that 

 other species migrate also at uncertain intervals. Mr. Green informs us 

 that Jamides hochus^ Cramer, does, and so also does Polyommatus boeticuSy 

 Linnaeus. We are not prepared to put forth any hypothesis to account 

 for this phenomenon, though it is a subject of great interest and well 

 worth study, but it requires a large number of skilled observers over a 

 considerable area and for several years, and unfortunately it is difficult 

 to secure these. The central mass of hills checks the spread of the 

 south-west rain from reaching the northern and north-eastern parts of 

 Xhe island, and consequently this climate is very hot and dry. Except 

 for an oQcaaional heavy downpour they are practically waterless, except 



