( liii ) 



Xaiithopan to the deep and naked cavity of Achcrontia and llerse is fonnd 

 in Megacorma and Coelonia. 



The third segment bears at the end a small and deep cavity of a sensory 

 nature. We have not studied this organ. 



The great variety in the structure of the antennae* of the Heterocera is 

 repeated to a lower degree in most families of larger e.xtent, and this makes it 

 generally impossible to give of these organs a short family diagnosis which is 

 trne of all the species of the respective groups. The stereotyped description 

 of the Sphingid antenna handed down from Linneau times applies only to a 

 portion of this family. The prismatic, clubbed, and hooked antenna is by no 

 means common to all the Sphingidae, a large proportion of the Hawk Moths 

 deviating widely from this type. However, comparing each type of antenna of the 

 present family with the corresponding types of other families, we shall always 

 find some difference, and very often some striking ditFereuce, revealed by the 

 closer examination of the special strnctnres. 



The generalised type of antenna of Lepidoptera is, in our opinion, that in 

 which the dorsal surface is wholly scaled, while the ventral surface is scaleless, 

 being clothed instead with a dense covering of fine hairs. This type is derived 

 from an antenna entirely ciliated. Besides the protective scaling and the sensory 

 ciliation there are other organs present, such as sense-bristles and -cones, both 

 of which are rather easily discernible and of considerable taxonomic value. The 

 scaling of the butterfly antenna is reduced apically and in a number of groups 

 altogether absent, except the first segments (Danainae, Pajtilios allied to 

 sarpecloiii etc.). In Heterocera we find the scaling extending to the last or 

 last but one segment, but meet also with antennae which have lost the scaling 

 {Saturniidae and close allies ; Pelochi/ta). The arrangement of scales in two 

 regular transverse rows on each segment which is prevalent among Butterflies, 

 and is found also in a very great number of Moths, does not obtain among 

 Hawk Moths except on the distal segments in a number of species, the scales 

 being comj)aratively small and ver}' numerous. Where among Butterflies and 

 Moths the area covered by the fine sensory ciliae is reduced, the ventral surface 

 becomes often partly scaled, the loss of the sensory function being followed by, or 

 going hand in hand with, the appearance of scales, in Lejndoptera the normal 

 clothing of the epidermis where no organs with special function are required. 

 The proximal segments of the antennae of Sphingidae are occasionally nearly or 

 totally scaled — namely, where the antenna is strongly clubbed. That means, 

 where the sensory function is more concentrated distally, the proximal segments, 

 which are reduced in width and function, have acquired an ordinary covering 

 of scaling on the underside. This is most evident in Rhopalopsyche, a genus 

 with also otherwise remarkable antennae. The appearance of scales as a sign 

 of loss of function, or of weakness, is strikingly illustrated by other organs. 

 We have seen above that the reduced tongue becomes scaled in some instances, 

 and that the bristles of the pilifer are replaced in many reduced species by 



* Comitare I'udiue, 'J'rant. Anicr. Ent. Sue. xxiii. p. 1 (IK'JG) ; Jordan, JVuv. Zool. v. p. .374 (1898). 



