332 
is voracious, and leads a different life from the quiescent, 
sleeping pupa or chrysalis, which takes no food ; on the 
other hand, the imago or butterfly has mandibles, which 
are rudimentary, and incapable of biting, while the maxilla, 
or ‘‘tongue,’? which were rudimentary in the caterpillar, 
become now greatly developed; and the butterfly takes 
Fig. 296.—Embryo of a 
Water-beetle (Hydrophilus). E, 
egg ; K, head ; o/, upper lip; m, 
mouth 5 an, antenne ; ,, man- 
dibles; 4%, &g, maxille; 3B, 
thorax ; 3), De, ba, legs ; Ay-hy0, 
ten pairs of rudimentary abdo- 
minal legs, of which all except h, 
disappear before the insect 
hatches; a, anus,—After Kowa- 
levaky. 
an ol } oG 
Fig. 297. Profile view of embryo 
paper lee, lettering as in Fig. 
296. BM, nervous cord; 0G, brain; 
D, digestive canal; sch, the ceso- 
phagus ; S¢, stigmatal epenings of 
the tracheal system; A, heart.— 
After Bliitschli. 
liquid food and but little of it, while its surroundings and 
mode of life are entirely changed with its acquisition of 
wings. Thus the butterfly leads three different lives, differ- 
ing greatly in structure, externally and internally, at these 
three periods, and with different environments. 
