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ward and forward migration at Bukit Kutu as well as other 
similar instances on record are to be interpreted by the causes 
shown to have been in operation by Major Pendlebury. 
Flight across the Wind wn British Guiana.—Mr. C. B. Williams, 
in Trans. Ent. Soc., 1917, p. 154, records the direction of 
migration of Callidryas eubule in fourteen localities in British 
Guiana, the observations in some of these having been repeated 
over a number of years. The butterflies always flew directly 
or obliquely across the prevalent N.E. trade wind, sometimes 
from N.W. to S.E., sometimes vice versa. That a definite 
directive stimulus is at work seems to be clearly proved, not 
only by these concordant observations, but by Mr. Williams’ 
account of a migration towards the $.E. which he observed 
in the North-west District, between Aug. 1 and 10, 1916. 
Throughout this period the direction of migration was resumed 
each morning after the night’s rest, and after interruption 
on Aug. 5, by a whole day of heavy rain, and on Aug. 9 by 
heavy showers. Furthermore, during intervals of cloud, on 
Aug. 8 the numbers became so few—3 seen in four minutes 
that each must have kept its direction without guidance by 
others. During the whole period the stream of migration 
proceeded, whenever it was resumed after the many inter- 
ruptions, ‘in a south-easterly direction at a speed of about 
twelve miles per hour across the prevailing north-east trade 
wind,” 
Mr. Williams’ records taken together strongly suggest that 
the direction of flight in C. eubule in British Guiana is due to 
reaction to the stimulus of the prevalent wind—a reaction 
such that the butterflies migrate backwards and forwards 
roughly parallel with the coast, and are not carried out to 
sea by flying against the wind or far into the interior by flying 
with it. Movement out of any area probably permits rapid 
recovery of the exhausted food-plant and the return of 
migrants from another exhausted area. Four of the migra- 
tions in the First Wet Season (May to mid-August)—Nos. 1, 
7, 8, 12—crossed the wind-current from W. to E., one— 
No. 5—from E. to W. Four of the migrations in the Second 
Dry Season (end August to October)—Nos. 2, 3, 4, 6—crossed 
from KE. to W., one—No. 13—from W. to E. These include 
