88 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 85 



seen at once between the retractile planta of the former and the gill- 

 bearing tubercle (Vs) of the latter. Moreover, the likeness amounts 

 almost to a structural identity when the planta is compared with the 

 claw-bearing lobe of one of the terminal appendages of the Cory- 

 dalus larva (fig. 36 E, Vs). In each case the organ is provided with 

 strong retractor muscles arising on the dorsum of the body segment. 

 It is a mere detail that the muscles in Corydalus (fig. 36 D, rvs) branch 

 to the several lobes of the gill tubercle ; in the terminal appendages 

 the bundle of retractor fibers (F, rvs) tapers to a narrow stalk inserted 

 at the bases of the claws exactly as in the foot of the caterpillar (fig. 

 37 D). The Corydalus larva lacks only the accessory muscles of the 

 planta arising in the base of the subcoxa. We can, therefore, scarcely 

 avoid the conclusion that the planta of the caterpillar's abdominal 

 leg is an eversible vesicle of the limb basis, here borne by the coxa, 

 which is not consolidated with the subcoxa. The representatives of 

 the styli, preserved in the movable distal processes of the sialid ap- 

 pendages (fig. 36 C, D, E, Sty), have been lost from the abdominal 

 limbs of all lepidopterous larvae. 



The anal legs, or appendages of the last abdominal segment of the 

 caterpillar, dififer from the legs of the preceding abdominal segments 

 only in details of their musculature. Their structure will be described 

 in the subsequent discussion of the terminal appendages of holometab- 

 olous larvae. 



The abdominal appendages of chalastogastrous hymenopterous 

 larvae have the same essential structure as the abdominal limbs of 

 caterpillars, though they are not so highly organized, and the plantar 

 lobes are reduced to terminal disks of the coxal segments (fig. 3 C). 



THE GONOPODS 



The appendages of the eighth and ninth segments of the abdomen 

 are potentially gonopods because of the association of the openings 

 of the genital ducts with these segments. They are, however, not 

 necessarily modified for reproductive purposes, as in the males of cer- 

 tain Thysanura in which the appendages of the eighth and ninth 

 segments (fig. 33 C) do not differ structurally from those of the 

 preceding segments. 



Typically a gonopod is distinguished from the pregenital and post- 

 genital appendages by the development of a median process from the 

 proximal part of its base. A complete gonopod, therefore, consists 

 of a hasal lobe or plate (fig. 31 B, LB), of a lateral, distal stylus (Sty), 

 and of a median, proximal gonapophysis (Con). Both the stylus and 



