174 THE CANADIAN ENTOMOLOGIST. 



THE HIND WINGS OF THE DAY BUTTERFLIES. 



BY A. RADCLIFFE GROTE, A. M., HILDESHEIM, GERMANY. 



I wish to offer here a few remarks on the structure of the hind wings 

 of the diurnals especially, in extension of my recent paper on the Butter- 

 flies of Hiidesheim.* 



The first point relates to the fact that the hind wings are more 

 specialized as compared with the primaries. The probable explanation I 

 offer is, that the hind wings bear more of the weight of the body 

 (abdomen), and that they regulate the downward stroke of the fore wings. 

 A parallel suggests itself with the vertebrates in which the hind legs are 

 more specialized; and the cause is then, in both cases, a mechanical one. 

 This specialization in the hind wings of the day butterflies manifests 

 itself primarily in the inequality of the wings, of which the secondaries 

 have the Radius r branched, the primaries 3 to 5 branched. In the 

 second place by an advance over the front wings in the process of the 

 absorption of the median veins, so that the radius or cubitus of the 

 secondaries draws the branches nearer to itself than the corresponding 

 vein of the primaries. Vein IVg, in the case where its condition is 

 not permanenlly generalized {Lycae/iidcr., Riodinidce, Hesperiidce), is 

 thus usually more drawn out of its original central position on the 

 secondaries ; it submits also first to degeneration {Hesperiidce) on the 

 hind wings, showing that here the cross vein has degenerated for a 

 longer period than in the primaries, isolating the vein and depriving 

 it of nourishment over a longer ancestral line. The cross vein itself 

 vanishes first on the secondaries. Here the cell may be open, all trace 

 of the scar vanished {Araschma, Melitcea), while on the fore wings the 

 degenerate vein is present, closing the cell. 



The progress in the evolution of the neuration is evidently taking 

 place in identical directions on both wings. The generalized condition 

 of the radius (it being 5 -veined) of the primaries in Papilio gives way 

 to a specialized condition (4-veined) in Parnassitis , with an intermediate 

 5-veined state in Thais, in which latter the upper branch of the median 

 series, vein IV, _ which has left the cross vein to emerge from the radius 

 in Parnassms, leaves the cross vein near the upper angle of the cell. 



The absorption of the veins is everywhere attended by the same 

 indications of a physiological process which, in its external manifesta- 

 tions, it is easy to trace. It is the same with veins II. and III. of the hind 



• — — 



*iVIittheilungen a. d. Roemer Museum, No. 8, Feb,, 1897, 



