( 556 ) 



(A) The veinlet D^ stands between M' and M- in both sexes: 



(B) The veinlet D' stands in ? between W and M-, in (S at jtoiut of origin of 



M' or close to it ; 



(C) The veinlet D' stands in both sexes at or close to the point of origin of M'. 

 If in bntterflies and moths the sexes are different in neuration, the discrepancy 



is mostly to be accounted for by the presence of special structures in the male, such 

 as scent and stridulatory organs, or by a difference in the shape of the wing. In 

 the case of Cliunu-es there must be another explanation of the difference of the 

 sexes in the position of D^ of the hindwing, for there are no structures in the male 

 wing that could influence the jiositiou of tliat veinlet, nor do the wings of the 

 sexes oi protocka, for instance, in which species the sexes differ in the position of 

 D', deviate more from each other in shape than they do in azota, in which the veinlet 

 is the same in jjositiou in both sexes. Hence it is obvious that the above cases 

 (A), (B), and (C), with intergradatious, represent stages in the luutation of the 

 neuration of ('//arctj-ex ; and it is furtlier clear that the mutation began with forms 

 iu which the veinlet had the same position in both sexes, began either with (A) or 

 with (C). As said on p. 440 of this volume, the question mostly so difficult to 

 answer is not, "Where is the road that Evolution lias taken ? but Which is the direction 

 in which Evolution has traversed that road ? Had the ancestor of C/mraxcg the 

 veinlet as in case (A) or as in case (C) ? Or in other words, considering (B), is 

 the J'l'.male the more advanced in mutation, or the male ? So much is snre that 

 mutation has been detinite in the case of Clutroxes, else there would be species in 

 which the veinlet D^ is more basal in the S than in the ? . 



The accompanying diagrammatic tignres show the position of the veinlet iu 

 question in a number of Lepidoptera the neuration of which may be taken as 

 representing various stages in the evolution of D' and R^ (but the Lepidoptera here 

 referred to are not meant to be ancestral forms of C/iara.res). In the chrysalis 

 of a Nymphiilid (Fig. 5) R" stands between M' and R-', and a connection between 

 R^ and M' is brought about by the development of a trachea D' (punctured in Fig. .j) 

 from M' that joins R^ ; in a similar way R^ becomes connected with R-. In the 

 wing of liejiialxis (Fig. 4) D' and D' are readily recognized as transverse veins, while 

 in Fiipitio (Fig. li) D' appears to be a i)rolongation of 51, 1)' remaining, however, 

 more or less transverse, but pointing somewhat distad; in Ilesfia (Fig. 7) D^ stands 

 at right angles to the middle line of the cell, and in Coduya (Fig. ^) it is somewhat 

 directed basad ; I'uliiiaga (Fig. IJ) has the veinlet thinner, longer, and more oblique, 

 and D* forms here a very blunt but distinct angle with W\ in Coeiiojihlebia (Fig. lo) 

 D' is very thin, D' and It" form no angle, D' appearing to be the basal portion of 

 W, and R^ stands as in the preceding figures outside of M' ; in Charaxes eupale 

 (Fig. II) W is very often placed just at the outer side of M', while in Charaxes pro- 

 toclea S (F"ig. 12) it joins il at the jioiut of origin of M' and in protorlen 9 (Fig. 13) 

 between M' and M-. It is evident from these figures that the cross-vein D' is an 

 accessory veinlet connecting originally the second with the third radial, there being 

 in the more generalized Lepidoptera and in the chrysalis no direct connection 

 between R- and M, and that the more basal position of that veinlet iu the imago of 

 CharaxeH and I'alla (and other yymphaUnae) is a later acquirement (tlie basad 

 movement having taken place in connection with a shortening of the basal partition 

 of the subcostal and a backward movement of R^). Hence the Cliaraxca with the 

 veinlet placed as iu Fig. 13 are, in respect of this single character, younger than those 

 Charaxes which agree with Fig. 11 and 12; and the development of the veinlet, 



