272 Dr. Frederick A. Dixey on the 
the nervules, though surrounded with black scales, are 
themselves covered with white, or (on the underside) pale 
yellow scales; a light-coloured centre being thus provided 
for the dark discoidal patch. In the genus Vatochila 
this light-coloured centre acquires greater importance. 
On the under surface of 7’. autodice the white scales are 
seen not only covering the disco-cellular nervules, but 
also intruding some way upon the yellow of the general 
surface; in this species, however, the pale patch thus 
formed has no dark border. But there can be little 
doubt, on a comparison of 7’. autodice with Colias palzno, 
that the whitish area surrounding the second disco- 
cellular nervule in the one is homologous with the silvery . 
patch in the corresponding region of the other; while 
the identity of the discoidal marks in Tatochila with 
those in Synchloe, and of the same marks in C. paleno 
with those in other species of Oolias, is a matter of 
certainty. ‘The brown ring surrounding the silvery 
pupil on the under surface of most species of Colias is 
indicated in C. paleno, where its general appearance 
points to the probability of its origin from the dark 
scales that have already been noticed as gathering about 
the region of the disco-cellular nervules in Synchloe. 
In C. palzno itself, however, the central pale patch (as in 
Tatochila) becomes far more prominent than the sur- 
rounding dark border. An examination of the discoidal 
spot on the underside of the hindwing in Gonepteryx 
rhamnt 9 and Amynthia merula will disclose the same 
general arrangement of a pale area traversed by the 
second disco-cellular nervule, and surrounded by a ring of 
darker scales, that we have already seen to be character- 
istic of the spot in other genera. In these insects, how- 
ever, as in I¢thodocera leachiana, the spots, though clearly 
identical with those in Colias, are in a lower state of 
development and specialization. ‘Turning again to the 
discoidal spots on the forewing, we may at first sight 
hesitate to identify the bright orange spots in G. rhamnt 
or G. cleopatra with the black spots or patches in 
Synchloe and Colias. But in Amynthia clorinde we have 
what is unmistakably an intermediate form of the spot, in 
which the vivid orange of the one closely encircles the 
deep brown or black of the other, and from which either 
the Gonepteryx or Colias type of spot might be easily 
derived. Much the same is the.case with /’. leachiana; 
