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VI. Some Notes on Butter fly Migrations in British Guiana. 

 By C. B. Williams, M.A., F.E.S. 



With Sketch Map. 



[Read March 7th, 1917.] 



The whole problem of the migration of insects, and of 

 butterflies in particular, is one of great interest, and, at the 

 same time, one about which we have so little data that it 

 is almost impossible at present to make any generalisations. 

 With the exception of records of such well-known migratory 

 insects as the locusts, most of the pubhshed accounts are 

 fragmentary, inaccessible or isolated records for a country 

 by passing visitors. From the records relating to butter- 

 flies almost the only common fact which emerges is that 

 migrations are particularly abundant in the Pieridae, 

 records in this group being known from all parts of the 

 world. 



I have recently spent a few months in British Guiana, 

 and have been fortunate enough to observe two migrations 

 of the yellow Pierid, Callidryas eubule, one of which lasted 

 for at least ten days. I also questioned a number of 

 residents of the district about migrations, which when 

 large are noticeable even by the non-entomological public, 

 and find that they are a phenomenon of regular occurrence, 

 and that almost every one who has resided there for any 

 length of time has seen the clouds " of yellow butterflies 

 all flying steadily in one direction." Most of the accounts 

 were too vague to be of any value, especially w^ith regard 

 to details ; but from among them I was able to get some in 

 which the locality and the direction of flight was given 

 with sufficient appearance of accuracy to make it seem 

 worth recording. Li addition to these I have given ex- 

 tracts from a few pubhshed accounts of migrations in 

 British Guiana, chiefly from local pubUcations which are 

 not readily accessible to the entomologist. 



The climatic conditions near the coast of British Guiana, 

 to which district most of the records refer, consist of two 

 wet and two dry seasons each year. In general, February 



TRANS. ENT. SOC. LOND. 1917. — PART I. (nOV.) 



