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general clear tint, reigning over the whole extension of the wings, 
as well as the similarity in design between fore- and hindwings, 
upper- and underside, impresses me as a secondarily acquired 
uniformity, rather than as a really original feature, 
In my opinion we meet here with a similar case as in the 
wholly selfeoloured butterflies e. g Gonepteryx rbamni 
or Aporia crataegi, in which without the least doubt the 
uniform hue is the consequence of the simplification of the shades, 
hand in hand with the total or partial regression of the markings. 
Still more striking is the similarity with the Parnassine butterflies 
(which, it need hardly be said, is of course wholly superficial and 
occasional). For in these as well as in Saturninae a set of highly 
differentiated eye-spots on the forewings, but still more pronounced 
on the hindwings, form the most conspicuous part of the pattern, 
though it may undoubtedly be taken for granted that the spotted 
design of the Parnassines has developed from a far more complete 
array of simpler and more uniform markings, such as are seen in 
Thais poly xena and its consorts. 
As soon as we consider the similarity of fore- and hindwing, 
upper- and underside of the female of pavonia and of both sexes 
of pyri and spini as secondarily acquired characteristics, there 
need no more be any objection against the supposition that the 
male of the first-named species is more original than the female. 
From this point of view we may further remark, that the existing 
contrast between the yellow upperside of the hindwing and the 
greyish one of the forewing, on which the markings are less hidden 
under the ground-colour, corresponds in a higher degree to the 
general type of butterfly-design than does the exact similarity of 
fore- and hindwing; the overwhelming majority of Lepidoptera 
showing a similar difference between fore- and hindwing. 
In the fact that the discoloration (in this case yellowing) occurs 
on part of the wpperside of the hindwing and of the underside of 
the forewing, the male of pavonia is in harmony with both 
sexes of Smerinthus ocellata and of many other Lepidoptera. 
Up to a certain degree the frequent occurrence and similar extension 
of this discoloration can be attributed to the influence of the resting 
attitude of these moths, the discoloured areas being exactly those 
which during this attitude remain covered by similar parts of the 
adjoining wing. In his paper: “Sur la position de repos des Lépi- 
doptères’’, J. T. Oupemans has directed our attention to this cir- 
cumstance and expressed his opinion that during the development 
and modification of the colour-pattern in the course of time, the 
