334 Mr. L. D. Cleare on 



An idea of the number of butterflies, even in a small 

 migration like this, may be gained by making a rough 

 estimate. Taking twenty butterflies per minute, crossing 

 a width of 120 yards, and taking the width of the swarm 

 to be about half-a-mile, this would give 8,760 butterflies 

 crossing per hour. This migration lasted for two and three- 

 quarter hours, which would give about 24,090 butterflies 

 in the swarm, and this would be a conservative estimate. 



Unfortunately none of the insects were captured, so I 

 can give no information as to the percentage of the sexes. 

 The species concerned, however, may, I think, be safely 

 put down as CalUdryas eulmle L. 



2. Mr. B. H. Gainfort, of Sprostons, Ltd., describes having 

 seen a very extensive flight of yellow butterflies, which, 

 as far as I know, is the broadest swarm on record. He 

 writes : "It was on the 6th July, 1912, going up the Deme- 

 rara River that we passed through a swarm of orange- 

 coloured moths (sic) so thick that we caught several 

 hundred of them from the deck of the steamer ' Essequibo.' 

 We entered the swarm somewhere between Diamond and 

 No. 1 Island and got out of it somewhere about Dalgin. 

 I estimated at the time that it was about 30 miles wide — ■ 

 flying from west to east. These moths (!) were in evidence 

 a day or two afterwards on the Essequibo and Potaro 

 Rivers." Obviously these " moths " were CalUdryas. 



Mr. E. E. Winter, B.Sc, Geological Surveyor of this 

 Department, has given me several observations. They are 

 particularly interesting on account of their being made in 

 the interior of the colony, and on account of Mr. Winter's 

 observation of their association with dry weather. 



Mr. Winter tells me that such migrations can invariably 

 be seen on the rivers during the dry season. Practically 

 on every trip he makes some such swarm is observed, 

 but the ones mentioned here stand out distinctly in his 

 memory above all others. They may be taken as typical 

 examples. . 



3. Mazaruni River, Makari Falls, October 1911. Dry 

 season. Mr. Winter was camped on one of the islands in 

 this fall. He observed " yeflow and washed-out green " 

 ( ? males or Pieris) butterflies crossing the river for about 

 eight hours, say between 7.30 a.m. and 4 p.m. The 

 insects were flying in twos and threes with varying dis- 

 tances between them ; they could never be described as a 

 thick cloud. Owing to the position of his camp, in one 



