( Iviii ) 



uml near allies,* but is lint identical with it, dctuirs only in two siiecies of 

 Am/julicinae, each representing a geuus of its own — namely, Monardu and 

 Cresaonia. In figs. 1 and 2 both kinds of Sjihingid pectinations aie incipient. 

 If the dor.so-lateral expansion (dip) Ix'caiue prolonged, the result would he a 

 pectinated antenna of the first type ; if the snbventral carinae (/c) became 

 j)rolonged, we should have a pectinated antenna of the second type. The dorso- 

 lateral expansion is very rudimentary in Monarda and Cresso/iia, and the upper 

 fascicles stand ajiart from it, having in a dorsal aspect (PI. LXI. f. o) the same 

 appearance as in ordinary fiisciculated antennae, this being a si)ecial feature of 

 the Sphingid bipectinated antenna. The asymmetry of the segment is distinct 

 in fig. 4. 



As said above, the fasciculatiou, ])ectiiiatioii, and the compressed shape of 

 the antennae obtain in a much higher degree in the male than in the female ; 

 very often the female antenna is simjile where the male antenna is complex in 

 structure. Now, the question arises. Does the simple antenna really represent 

 the more ancestral state of development as maintained above, or is the simple 

 cylindrical segment derived from a more complicated segment in consequence 

 of the reduction or loss of the special structures ? Poulton, from researches on 

 the pupae of some Saturniidae, came to the conclusion that the second alternative 

 was correct — namely, that the short-branched Saturniid female antenna was a 

 development by reduction from a longer-branched antenna. Though the con- 

 clusion was perhaps rather hasty, inasmuch as the fact was not taken into 

 account that the specialisations of the male are often transplanted on to the 

 female, it was nevertheless suggestive, and served to draw the attention to a 

 neglected point. If one considers the case of the similarity in the sexes of 

 Rliojtalofjsi/che by itself, one must come to a conclusion similar to that arrived 

 at by Poulton. For the absence of fasciculated ciliae from the male of Rhopalo- 

 pgijche cannot be explained by assuming that this genus had preserved the 

 original simple state of ciliation ; such an explanation seems to us to be almost 

 absurd, coniridering that Rhopalopsijche is in all other respects very specialised, 

 and is the only excejition from the rule among all the Sphingidae. And 

 therefore there remains only the second alternative — that the male antenna of 

 Rlwpalopsijc/ie has lost the fasciculated ciliae, and thus become simple. If that 

 is true — and it cannot be seriously doubted, we think — one might conclude with 

 some degree of justification that the same line of development from the com- 

 plicated to the simplified observed in this male obtained also in the female sex 

 of Sp/khigidae ; that is to say, that the simple female antenna of Sphingidae 

 was a derivation from a fasciculated female antenna. And it might further be 

 advanced, as a confirmation of the evidence upon which that conclusion is based, 

 that there is a wide-spread tendency of retrogressive development in Sphingidae, 

 to which we shall have to draw attention in many places of this Revision. 

 However, when we take into consideration the two types of pectinated antennae 

 found within the same subfamily of Sphingidae {Ceridia, PI. LX. f. 27. 28; 

 • Smith, Ent. Amer. iii. p. 2 (18S7); id., Trans. Amer. Ent. Soo. sv. p. 230 (1888). 



