( Ixxxiii ) 



and euphorhiac also do not show any ii]ii)iirent differences. Profnpnrre Jiorestan 

 and CIdaenoijrammajasmiiieKrum, thun^li g-enerically distinct, have the same sexual 

 armature. This kind of identity slionld not be confounded with similarity arising 

 out of reduction. It happens that members of different subfamilies become similar 

 in one or the other organ in conseijueuce of the loss of special structures. iSuch 

 species are, however, never the same in all parts of the copulatory apparatus, as 

 is the case in the insects mentioned before, the list of whicli is by no meaus 

 exhausted by the few species used as illustrations to show that it is quite erroneous 

 to maintain that all specifically distinct Lepidoptera exhibit differences in the 

 copulatory organs. 



(2) Species which are different from the nearest relatives, but do not show 

 any marked geograjihical variation in the sexual armature.— Here belongs by 

 far the greater proportion of the Hawk Moths. The sjiecific differences are very 

 slight or very conspicuous, or intermediate in degree. They may be found in one 

 single organ, or in more, or in all. The differences may be slight in some 

 species, and great in others of the same genus. Two species may differ strongly 

 in external features, and little in the sexual armature, or the reverse may be the 

 case. There is every conceivable gradation in this respect. There is always 

 some individual variation, as a matter of course. When examining the 

 armature of only one individual, one is sometimes induced to consider a certain 

 outline or structure as specific, while it is in fact only an individual character; 

 if possible, a number of specimens from different localities should be examined. 

 Individual variation is most obvious in species with complex structures, but it 

 is here far less easily misleading than in the case of simple structures, because 

 the specific differences are as a rule more conspicuous there than here. 



(3) Species which differ in the copulatory organ from the allies and vary 

 in themselves geographically.— Geographical variation is most often met with 

 and is most conspicuous in those forms which are sedentary in habits. Sluggish 

 species with functionless mouth-jiarts and reduced power of flight, species of 

 which the sole function as imagines is ]iropagation, are especially liable to 

 develop into geographical races with differences in the sexual armature. The 

 phenomenon occurs often among Anibuliciime. The geographical differences in 

 these organs, which may or may not be accompanied by differences in external 

 features, are occasionally surprisingly great. In Pseadoclanis postica from 

 West and East Africa (PI. XXXII. f. 12. 13), and Polyptijchus trilineatiis'Jvom 

 Ceylon, North India, and the Philippines (PI. XXV. f. 2; PI. XXXIV. f. 7—10), 

 we have extreme cases of geographical variation in the copulatory organs, 

 which cases are the more instructive as the races exhilnt only slight external 

 differences. Oxipunbuli/x sabstrigilis (PI. XXX. f. 3. 4. 5) is also an example 

 to the poitit. It is quite erroneous to say that differences iu the sexual armature 

 are always of specific value. Geograi)hicaI races may be different or not in 

 these organs ; and the difference may be minute or conspicuous. It is idle to 

 maintain that geograjihical representatives are specifically distinct, if the sexual 

 armature shows obvious differences. What one investigator considers obvious 



