18 



THE CATERPILLAR. 



an armor-like shell which hardly allows any- 

 thing more than a lateral motion [Fig. 23] ; while 



FIG. 23. Metatho- 

 racic leg of cater- 

 pillar of Papilio 

 Antiopa, X 3J. 



Fio. 22. Caterpillar of Danais Plexippus, nat. size (Riley). 



the proleg is a fleshy stub which may be with- 

 drawn or extended at pleasure, and is armed 

 at tip with several curving series of 

 NTX, delicate hooks [Fig. 24] ; these also 



\L are extensile and will grasp a sin- 



gle thread, or plunge themselves so 

 firmly into a silken carpet that it 

 would require considerable force on 

 our part to extricate them ; while a simple mus- 

 cular movement of the caterpillar serves to with- 

 draw them from the web, leav- 

 ing not a thread misplaced. 

 The presence or absence of the 

 horny jointed legs separates 

 the segments of which the body 

 is composed into two tracts, the 

 thoracic and abdominal ; this 

 separation, however, would not apparently have 

 much weight were it not for the future development 



FIG. 24. Caterpillar of 

 Papilio Antiopa ; . proleg, 

 X 4t ; b. circlet of hooks at 

 end of proleg, X 5 ; c, one 

 of the hooks, X 12. 



