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TEXT-BOOK OF ENTOMOLOGY 



there and then a large imaginal bud with a circular invagination. 

 These buds were noticed by Lyonet, who supposed them to be 

 "' les principes des jambes de la phalene." Nerves and a tracheal 

 branch penetrate into the femoro-tibial bud and form a small bay or 

 constriction which marks the point of junction of the femur with 

 the tibia, and the body-cavity remains in direct communication with 

 the end of the limb. 



The tarsus undergoes a series of changes ; the surface is folded in 

 a very complicated way ; at the level of each articulation, but only 

 in the internal and concave region of the leg, is developed a deep 



fold ; on one side there is a hypodermic 

 thickening, on the other a simple leaf 

 of the envelope, which afterwards joins 



ff- 



..A. 



FIG. 60S. Feet of the Pieris but- 

 terfly withdrawing from those of the 

 larva. 



FIG. C09. Imaginal feet of Pieris uncovered with 

 great care to preserve the position which they had in the 

 larva : ta, tarsus ; , tibia ; g, knee ; f, femur ; ft, coxa. 



at its base with the parietal hypodermis, and then two leaves are 

 destroyed with the large cells of the setae. The internal part and 

 end of the tarsus are then reconstituted with the elimination of the 

 debris, while the external and convex region undergoes direct 

 regeneration. 



The coxa and trochanter are derived from the base of the larval 

 leg, and only the 1st pair are well separated from the base of the 

 thorax. One or two days before pupation the femoro-tibial bud, after 

 having, until now, preserved its antero-posterior direction, is placed 

 transversely as regards the larva, then becoming directed obliquely 

 forward. This rotatory movement of the coxa may be attributed to 

 the great extension of the fore wings, which push before them the 

 two first pairs of legs. The last pair in their turn are simply covered 

 by the hind wings and are but slightly displaced. This new position 

 of the legs is that of the imago : the knee of the 1st pair is situated 

 in front of the tarsus ; that of the 2d a little outward ; that of 

 the 3d pair is directed backward. (Gonin.) 



The antennae. - - These appendages also have the same relation with 

 those of the caterpillar as in the case of the legs, the larval append- 



