Te ae 
XIX 
all the records with sufficient data, omitting No. 14 in the 
interior, where the seasons are different. Thus in the coastal 
zone the great majority of the wet-season migratious were 
down the coast, viz. towards the borders of Dutch Guiana, 
while an equal majority of the dry season were up the coast 
towards the Venezuelan border. 
It would be of much interest to determine whether the 
migrants which reach any area are the descendants of those 
which formerly left it. The return migration, which took 
place about two months after the flight described by Mr. 
Williams (ibid., p. 159), certainly suggests although it does 
not prove this conclusion. 
While the observations on C. ewbule were remarkably con- 
cordant and support the conclusion that this species has 
locally developed a favourable reaction to the prevalent wind, 
the single example of migration by Appias margarita, No. 16, 
apparently exhibits a reaction of the opposite kind, the stream 
of butterflies having been seen by Mr. A. Leechman for over 
three days flying obliquely against the wind, viz. in a direction 
which carried them out to sea (ibid., p. 163). 
The evidence, so far as it goes, suggests that the Pierine 
which migrates frequently exhibits a more favourable reaction 
to the local wind-current than the Pierine which migrates 
comparatively seldom. 
This interpretation of the behaviour of C. ewbule is not 
intended to imply that the direction of its migration is in- 
capable of modification by other causes. Mr. Williams’ map 
on p. 156 strongly suggests that the wide river Essequibo 
and the line of the coast may influence the direction, and, 
on p. 160, it is shown that the suddenly increased strength of 
the N.E. wind deflected a northerly flight towards the west. 
Migration of Catopsilia statira in Trinidad.—Mr. C. B. 
Williams’ interesting and detailed observations of a large 
migration of this species (Trans. Ent. Soc., 1919, p. 76) show 
that the general movement was westward, parallel with the 
N. coast of the island and the adjoining Venezuelan coast, 
viz. such as to carry the streams across to the mainland. 
And, in fact, Mr. Williams concludes with certainty ~ that 
the greater number left the island.” The flight took place 
