460 MAJOR F. C. FRASER ON 
Genus VESTALIS. 
25. V. APICALIS Selys. 
Six ¢ and seven 2. The apical marking varies in density 
but none of the specimens are as dark as specimens from Malabar, 
India, 
Genus MNAIs. 
26. M.EARNSHAWI Williamson. 
Four ¢ and four 2. Some of the specimens are in a teneral 
condition. From Dran 3000 ft. and Dalat 5000 ft., Langbian Province, 
March to May, 1918. 
The eight specimens of this very interesting insect exhibit 
well the remarkable polymorphism of the rudimentary pterostigma, 
which is clearly undergoing a gradual reduction. Indeed, by a com- 
parative examination of the material at hand, it is possible to trace 
the complete process of reduction from a moderately large and well- 
defined pterostigma to a complete obsolescence as found in Vestalis. 
In the same specimen, the pterostigma is seen to vary in all 4 wings, 
Pterostigma of M. earnshawi, arranged in series to show 
the gradual reduction which is taking place. 
especially in the females, in one of which it is entirely absent and in 
two other wings it is merely indicated by the faintest shading about 
one of the postnodal, apical nervures. In other wings, it is of the 
palest grey or entirely hyaline so that some difficulty is experienced 
in determining which cell represents the pterostigma. In the males 
it is a deep blood-red and may overflow its bordering nervures so 
that it appears to be traversed by the same. In reality this appear- 
ance is apparently due to a gradual contraction in the size of the 
stigma so that the bordering nervures are being left behind, a pro- 
JOURN, NAT. HIST. SOC, SIAM, 
