xrv 



these cases upon the upperside of the primaries (see Plate XIX, i2ab, ij^ab, 

 1 8a), in the same place, that is, as where the white remains the longest in the 

 males of Mileius Symethus Cram. This stripe, also, presents just the same 

 condition, a far advanced covering of the white by a darker pigment. But, for 

 the rest, there is here a great difference. In the Allotinus species, it is not 

 only the males that are so far advanced in the darkening process, but the 

 females also, and these even to a greater extent. For the Allotinus females 

 are even darker than the males, the dark pigment is more predominant, and 

 the relic-stripe is even more indistinct than in the males, the white seems to 

 be still more reduced, and almost to have completely disappeared. In these 

 species it is therefore clear that the females are further advanced in the evolutio- 

 nary process of darkening than the males and therefore that they probably 

 entered upon it earlier, showing thereby that they were more susceptible to it. 

 Here we have, as regards this evolution, what is called sexual prefonderance, 

 in the Miletus species masculine, and in the Allotinus species feminine. 



Thus it may be seen that the study of these relic-stripes is very illumi- 

 nating. It makes it clear that the change of colour in the Lepidoptera is an 

 evolutionary phenomenon. It shows moreover that the course of such an 

 evolutionary process is not always the same, that in nearly related species it 

 may occur in the one while the other remains unchanged, and that where it 

 occurs it may develop much more rapidly in the one sex than in the other, 

 so that either of the two sexes may occupy the more advanced stage, and that 

 in this respect the initiative of the male sex which was formerly maintained, does 

 not exist. It shows that the susceptibility to such evolutionary processes differs not 

 only according to the species, but also according to the sex and even the indi- 

 viduals. And finally, that the course of such processes is very gradual, at least 

 as a rule, and by no means takes place by sudden charges, so-called mutations. 



Other species of Allotinus, seem however im this respect to be in a 

 different condition. One species A. Subviolaceus Felder, (PI. XX 20a) precisely 

 resembles many Lycaenae in which the dark pigment is decreasing; like these 

 it shows a faint structural colouring upon the upperside of the primaries. In 

 another species A. Nivalis Druce (PI. XX i g), the upperside shows a brownish 

 colour such as is caused by darkening in the above mentioned Allotinus 

 species, but the underside is almost entirely white; dark pigment hardly exists, 

 it is chiefly represented b)' a peculiar circular black spot. Similar spots are 

 also found in various species of Lycaena, in L. Hylax F. (PI. XX 2(^ab) and 

 L. Malaya Horsf (PI. XXI t2ab), for instance, and especially in L. Puspa Horsf. 

 (PI. XXII 74^1^), in the last they are unmistakably a relic, the remains of a 

 former general darkening. This compels us to attribute the circular spots in 



