( Ixxxviii ) 



Asj'iumetn- is also obscrvi'd in the annatiire (if tlie penis-fiinnel— for instance, 

 ill Xi/ci'ri/x eiicea (PI. LIU. f. 44). 



Another kind of asymmetry occurs m the legs and antennae. Here the 

 ditference is not observed in the ajipendages of the left and right side of tlie 

 body, but in the right and left side of the appendages themselves. The antennae 

 and legs are on the whole cylindrical, bnt in most instances the internal and 

 external sides are more or less dilfereiit. This is especially noticeable in pectinated 

 antennae, and in the spines of the tibiae and tarsi. 



Besides the diti'erences in the genital armature and in the frenulum and 

 retinaculum, the two sexes of the ,Sphinylilae show very obvious distictious in 

 other organs. These distinctions are the result either of the different develop- 

 ment of one or the other organ in the two sexes, or of the ajipearance of 

 special structures confined to the male. The sexual dimorphism is accordingly 

 relative or absolule, the former being for more frecjuent among the Sphingidae 

 than the latter as regards variety in the differences. One absolute sexual 

 distinction occurs in all species of Hawk Moths. This is a scent-organ* 

 situated at the base of the abdomen. It is found in all species. The orifice 

 of the organ lies in the pleural membrane above the upper edge of the basal 

 sternite (PI. LXIII. f. 1.2, gl). It is a cavity from which protrudes a bundle 

 of long scale-hairs, which serve as distributors of the scent produced by the 

 scent-cells. A groove or fold runs backwards from the orifice of the cavity 

 over the pleura of the third segment, ending on the fourth. The tuft is 

 sometimes retracted into the cavity, but frequently I'rojects in the dry cabinet- 

 specimens. Its colour is occasionally carmine or pink (Temnora). The organ 

 is essentially tlie same as that found in some Notodontidae. 



Another scent-organ is found on the hinder side of the anterior coxae.* It 

 occurs in all group.s of Spkingidai', but is very frequently absent or vestigial. 

 The difference ia tlie degree of development is often very pronounced in closely 

 allied sjiecies. In Coelonia fulriiwtuta the organ is very strongly developed, 

 while it is vestigial in Coelonia solani ; and Chromis erotus and heUodes differ in 

 a similar way. The organ is more often preserved and on the whole more 

 prominent in the Spliingidae semanophorae than in the Sphingidae asemanophorae 

 {Aclierondinne and Ambidicinae). 



A tliird scent^organ is met with in one species only of PInlampelicae — 

 namely, in Macroglossuin (/odej/'roiji. In this insect the mid- and hindtibia are 

 the bearers of tlie organ, whicii consists of a subbasal groove, situated on the 

 outer side, and of a large tuft of hair-scales. 



In the cT of Sesia fadiis th(^re is a black tuft of scales at the base and 

 another near the apex of the foretibia, not met with in the other species of 

 Sesia. We do not know the nature of these tufts. 



In the genus Kpistor we find a peculiar scent-organ on the forewiug, 

 reminding one very much of similar organs observed iu JJthosiinae. The cell 

 of tlie forewing of the males of Epistor gorgon, E. taedium, and E. carifer is 



• Haase, Iris i. p. 1^9 ff. (1W7). 





