17 



first two pairs of prolegs, but the young larvaj of Heliothis peltigera 

 uses all alike. 



It seems rather strange that in the PieridcB the larvse are born 

 with a complete circle of crotchets to the prolegs. Pieris daplidice 

 has in the first instar a complete circle of from fourteen to sixteen 

 crotchets. In the second instar the larva has an inner row of about 

 a dozen crotchets and an outer row of a few smaller ones, with entire 

 breaks between the two rows. The prolegs in the third instar carry 

 an inner row of from sixteen to twenty crotchets, and an outer row 

 of from three to six small ones. In the fourth instar the outer 

 crotchets have disappeared, and there are two rows of crowded 

 crotchets, about forty altogether, on the inner side of the foot, and 

 just outside these there are from eighteen to twenty larger crotchets, 

 but all towards the inner side of the leg. Unfortunately, I have no 

 note of the crotchets in the fifth or last larval instar, but presume 

 they would be similar to those of the fourth instar. 



From such meagre facts it would not be safe to generalize at all ; 

 but it appears that in the lepidopterous larva the thoracic legs were 

 first developed, and that when the prolegs appeared they had no 

 crotchets, but subsequently developed a circle of them, of which the 

 inner half only now persists in the full-fed larvae of some of the 

 higher forms of Lepidoptera ; and lastly, that the number of crotchets 

 per proleg is larger in the higher forms than in the lower, although 

 they are confined to one side of the foot. 



