Ixvi 



an easterly direction about 6 p.m. From that time onwards 

 the numbers steadily decreased. Many swallows were usually 

 circling round at the time, but I did not see any of the insects 

 taken. As a rule the insects were never more than about 

 20 ft. above the surface of the ground when passing the crest. 



" The phenomenon was repeated in the opposite direction 

 in the early mornings, 6.30-8 a.m., the numbers being approxi- 

 mately the same, so far as I could judge. Mr. T. R. Harvey 

 captured some of the specimens in a similar manner to mine', 

 viz. by standing in the narrow part of the ridge and utilising 

 opportunities when the insects flew low (5-8 ft.). Odd speci- 

 mens of the butterflies were taken during the day-time between 

 10 a.m. and 2 p.m., but in no case was a moth cajitured between 

 these hours. 



" The flight was repeated every evening and every morning 

 while I was at the bungalow except that on two evenings, 

 which were very wet, only a very small number passed over. 

 The fact that large numbers j^assed back next morning suggests, 

 however, that the insects may have flown over later the 

 previous evening. There was not sufficient difference in the 

 mode of flight for me to distinguish moths from butterflies, 

 and in fact I did not notice the difference clearly until getting 

 back here." 



Dr. DiXEY made the following comments on Delias in the 

 above communication : — 



Of the six specimens of the Pierine genus Delias which are 

 included among the insects received by Prof. Poulton as having 

 formed part of the migratory flight observed at Bukit Kutu 

 in Selangor, three (two males and a female) are Delias pyramus, 

 Wall., and three (all males) are Delias ninus, Wall. These 

 two forms of Delias, though closely allied, are quite distinct. 

 The most obvious differences between the males are as 

 follows : — ■ 



(1) In D. pyramus the yellow of the hind- wing upperside 

 does not generally extend outwards further than to the 1st 

 branch of the median vein; in D. ninus it always reaches 

 at least as far as the 3rd median, and extends beyond this 

 in the form of a slight yellow powdering usually as far as 

 the 2nd branch of the subcostal. 



