28 SPHINGIDiE. 



The ninth and tenth segments are fused into one (fig. 7 B, C) 

 and covered with bristles. Between the two halves of this 

 double segment lies the anus, and, ventrally to the anus, the 

 aperture of the oviduct. The segment is always short in 

 SPHiNGiDiE, and there is no ovipositor. The vagina lies 

 between the seventh and eighth sternites, and the orifice 

 is surrounded by more or less obvious folds, ridges, processes 

 and grooves. 



The part of the vaginal area in front of the orifice is termed 

 the antevaginal plate, and the posterior part the postvaginal 

 plate. 



Besides the vaginal ventral area there is the eighth tergite. 

 This is covered by the seventh, is never spinose, and varies 

 in size and shape. 



Scent-organs. — One absolute sexual distinction occurs in 

 all 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 (fig. 6 A, gl). It is a cavity from which 

 protrudes a bundle of long scale-hairs, which serve as dis- 

 tributors 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. 



Another scent-organ is found on the hinder side of the 

 anterior coxa?. It is very frequently absent or vestigial, 

 and is on the whole more prominent in the Semanophorse. 



Ill— HABITS. 



The moths have the habit, unique among lepidopterous 

 insects, of feeding and of depositing their eggs while hovering 

 on the wing. 



The eggs are usually laid singly on the underside of a leaf 

 or on a twig of the food -plant, to which they firmly adhere. 

 Owing to the crepuscular habits of the moths the method 

 of depositing the egg cannot often be observed, but in some 

 of the day -flying species the moth lays the egg while poised 

 delicately on the wing. The moths, by some means which 

 is not understood, select with marvellous accuracy the 

 particular plant or plants which will form the food of their 

 progeny, though an egg may occasionally be found on a blade 

 of grass close to the food. A few species, such as Celerio 

 euphorbias, in the West Himalayas, deposit their eggs in 

 batches of twenty or more on the underside of a leaf of 

 a gregarious species of spurge, close to the ground, and in 

 this species the larva? live gregariously, a dozen or more on 

 one plant. Clanidopsis exusta often lays its eggs in pairs, 

 and Mell states that the moths of the genus Parum usually 



