THE I'AMILY I'APILIONIDAE. 1031 



the wliolc of wliic'li seems iulapted to its reception. In tlie Lycaenidae 

 scarcely more than the anterior half of the available surface is put to use. 

 In the Ilospcridac, on tiie otiicr iiaiid, the cornea extends over the entire 

 area. In this |>articular the Papilioninac show the greatest rcscmlilance 

 to the Hesperidae, since only a very small portion of the posterior border 

 is lost. If we take the entire structure of the front of the head, we shall 

 notice, as we have pointed out in the analytical table at the beginning of 

 this work, that the marked width which is a characteristic feature of the 

 head of the Hesperidae is most nearly approached in that of the Papilio- 

 ninae, where the front between tiie eyes is of about ecjual width and 

 height. (Ither features of the head tell a similar story ; for instance the 

 brevity of the palpi, carried to an excess in most of the Papilioninac, is a 

 general feature also of the Hesperidae, although the palpi have here a 

 very different development by their stoutness and compactness, and by 

 their clothing. One of the striking features of the structure of the Hes- 

 peridae is found in the recurved antennal club ; this is very marked in 

 many instances, though in some, sudi as the genus Hesperia, it is com- 

 {)aratively slight ; the antennal club of the Papilioninae as a whole, in its 

 arcuate curve and general form, closely resembles the modified type of 

 structure which we find in the genus Hesperia ; and this is true of no 

 other group of butterflies, with the single exception of some limited 

 divisions of the Nymphalidae, such as the Euploeinae. Or if we pass to 

 the structure of the wings, there is no part of the body which will better 

 bear out the claim for a close affinity between the Papilioninae and the 

 Hesperidae : differing so strikingly as these members do in their general 

 form and size, there is nevertheless a wider departure from other groups 

 and a closer agreement between the two groups themselves in the general 

 plan of their neuration than can be found in any other two equivalent 

 groups in the whole range of butterflies. We have, for instance, in these 

 two groups, and in these only, four branches to the median nervure of the 

 front wing, and not infrequently to the hind wing ; so, too, we have in the 

 subcostal nervure of the hind wing only two branches in these two groups, 

 while in all other divisions of butterflies this nervure supports three 

 branches. No cases of parallel importance can be pointed out in the 

 whole series of the diurnal Lepidoptera. The inner border of the hind 

 wing is folded longitudinally in narrow plaits in the Papilioninae just as it 

 always is in the Plesperidae and very rarely in other butterflies. More- 

 over, as we have elsewhere pointed out, this is utilized in many males for 

 the concealment of the peculiar sexual hairs, in a manner very similar to 

 the same contrivance in the costal fold of the fore wings of many male 

 Hesperidi, and quite unlike anything else in other butterflies. The way, 

 again, in which the metathorax is marked off in a distinct way from the 

 mesothorax in Papilioninae finds its best counterpart in the Hesperidi ; 



