( Ixxxviii ) 



Asyiuimtrv is iilso oliscrvcd in the armatiive of the jieiiis-funiu'l — for instance, 

 ill yi/rrnjx e.rimi (PL LI 11. f. 44). 



Another kind of iisymuietry occurs in the legs and antennae. Here tlie 

 ilill'cieiicc is not observed in tlie appendages of the left and right side of the 

 iiody, liut ill tiie right and left side of tlie appendages themselves. The antennae 

 and legs arc on the whole cylindrical, but in most instances the internal and 

 external sides are more or less different. Tiiis is especially noticeable in pectinated 

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



l^csides the differences in the genital armature and in the frenulum and 

 retinaculum, the two sexes of the Spltinyidae show very obvious distictions in 

 other organs. Tiiese distiiulions are the result either of tlie different develop- 

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

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

 relative or absolute, the former being far more frecjueut among the Spldngulae 

 thau the latter as regards variety in the differences. Oue 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 iu all species. The orifice 

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

 sternite (Fl. LXIII. f. 1. 2, (jl). 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 projects in the dry cabiuet- 

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

 is essentially tlie same as that found iu some Notodontidae. 



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

 occurs in all groups of Sphinyidae, but is very frequently absent or vestigial. 

 The difference in the degree of development is often very pronounced in closely 

 allied species. In Coelonia fnlrinotuta the organ is very strongly developed, 

 while it is vestigial in Coelonia soluni ; and C/iroinis erotiis and heliodes differ in 

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

 prominent in the Sphinyidae semanopliorae than in the Sphinyidae asemanophorae 

 {Acherontiinae and AmbuliciiKte). 



A third scent-organ is met with iu one species only of I'ldlampelicae — 

 namely, in Macroglossum yodejf'roiji. In this insect the mid- and hindtibia are 

 the bearers of the organ, which consists of a subbasal groove, situated on the 

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



In the i of tiesia fadus there 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 Epistor we find a peculiar scent-organ on the forewing, 

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

 of the forewing of the males of Epii^tor yorgon, E. taedium, and E. cari/er is 



' llaasc, Iih i. p. 159 ff. (1887). 



