C 402 ) 



the extendodly senleil antenna nre absent, the stalk, at least, lieing always fnlly 

 scjiled in the species with a densely scaled urea : and it is nut admissible to explain 

 the absence iif iiitergradations by the assumption that the inter;Lrraduiite forms are 

 lost, bnt have been there in the course of the phyletic development of the Bntterflies, 

 because the s])ecies without and with extended dense dorsal scaliofr are often mnch 

 too closely related in other respects to warrant the all-round (lisa])i)earance of inter- 

 graduate forms. Moreover, the scaliufr is not in all species dense. The many forms 

 in which the scaling, though found on all the joints of the stalk and on the proximal 

 joints of the club, is sparse, or in which the scales are small (C/iaraxes, many 

 Neotrojtiyme), preserving sometimes only a few scales on each joint (Jfrsupia), and 

 thus representing intergradations between the densely sealed and nakeil antenna, 

 show that most probably the first step towards tlie disa]>pearance of the dorsal 

 scaling was that the scales became more scanty, or smaller, or both. 



The highly remarkable facts (I) that we find in Heterocera (apart from Jugatae) 

 the dorsal side of the antennae either bare of scales and of sensory hairs in relatively 

 few forms I^Sntnrtiiiriue, ('eratocampii/ae, Ameriln), or covered witji scales up to 

 the last joint, there being to my knowledge no such stages of development found in 

 which a larger or smaller number of distal joints is dorsally naked, as is so often 

 the case in Butterflies ; (2) that all the lleiijie.riiflae agree with the bulk of the 

 Moths in having the dorsal surface entirely covered with scales, and have, besides, 

 in all the members of the family at least the stalk covered with scales also ventrally ; 

 (3) that the Dismorphiinae, which are also highly specialised in the development 

 of the scaling, show a high degree of specialisation in other antennal organs in every 

 species ; and (4) that in all the forms of Danahiai' the dorsal surface is naked 

 (except the basal joints) in conse(|uence of obliteration of tiie scaling, — all jwiut in 

 the one direction, namely that, when a high degree of specialisation is reached, the 

 forms are relatively very constant in respect to that character. Hence it does not 

 seem to me to be rash to conclude, that also in the families where only a certain 

 number of species is highly specialised in the antennal scaling, this specialised 

 character is not easily, if at all, liable to further mutation, and that consequently the 

 species in which the distal joints are bare of scales and sensory hairs are probably 

 not derived from forms which were so highly specialised as to have the entire 

 dorsal surface of the antennae scaled, but from less s])ecialised forms in which the 

 distal joints had a covering of sensory hairs, which obliterated. 



The principal conclusions relating to the develojiment of the dorsal scaling are 

 these : the ancestor of Bntterflies had a dorsal covering of fine sense-hairs which 

 became modified into scales in a basi-apical direction : iiiitennae with more extended 

 dense scaling are derived from antennae with less extended scaling : antennae with 

 the distal joints bare of scales are derived from such in which these joints were 

 covered with sensory hairs ; antennae with sparse scaling (in a state of obliteration) 

 are derived from .antennae with dense scaling, the process of obliteration resulting 

 in naked antennae ; naked antennae can also be derived directly from antennae 

 with dorsal covering of sense-hairs. 



Now, the ventral side of the antennae having in many species of all families of 

 Butterflies except Ilesperiidae a covering of sensory hairs all over, must have been 

 without scaling in the ancestral forms of these families. The scaling appears first 

 on the proximal joints, where it is found in many s])ecies which have the rest of the 

 under surface provided with hairs, and the development ])roceeds in a basi-apical 

 direction as on the upperside. The end of this line of development is, however, not 



