654 TEXT-ROOK OF ENTOMOLOGY 



they appear early at the surface. This origin of the legs, thanks to 

 Weismann, Kunckel, and Van Rees, is well known in the Diptera ; 

 in the Hymenoptera it has been proved to be the case with ants by 

 Dewitz, and in Encyrtus by Bugnion. As for the Lepidoptera our 

 knowledge that the legs of the imago arise from the six thoracic 

 legs of the caterpillar, up to the date of Gonin's paper has not been 

 in advance of that of Malpighi and Swammerdam. 



Re'aumur, moreover, was supposed to have furnished the proof, having from 

 his experiments concluded that " if the legs of the pupa appear longer and larger 

 than those of the caterpillar wherein they were contained, it is because they 

 were folded and squeezed." (8 e Me"m., p. 305.) 



This explanation of Reaumur's has been generally accepted. Graber (Die 

 Insekten, p. 506) accepted it, after examining microscopic sections of the legs, 

 and Kunckel averred that " Reaumur, having, in certain caterpillars, completely 

 cut off one of the thoracic legs, had concluded that the butterfly which came 

 from it lacked the corresponding member." (Rech. sur 1'org. et d6v. des volu- 

 celles, p. 160.) 



Newport, it is true, denied this disappearance of the legs, but did not wish to 

 put himself in opposition to received ideas, and supposed that the member cut 

 off was partly reformed in the imago. 



Kunckel believes that he has found a better solution in his theory of histo- 

 blasts or imaginal buds ; in his opinion, " Reaumur and Newport are both right," 

 but "when Re'aumur cut off a caterpillar's leg, he at the same time removed the 

 histoblast, the rudiment of the leg of the butterfly. When Newport repeated 

 this experiment, he simply mutilated the histoblast without completely destroy- 

 ing it : in the first case, the adult insect was born with one leg less ; in the 

 second case, it appeared with an atrophied foot." 



"So ingenious an explanation," says Gonin, "is not necessary." To prove 

 that the experiments of the two savants are not contradictory, it would have 

 been sufficient to cite, as Kunckel did not do, the exact words of Re'aumur, for he 

 having cut from a caterpillar " more than half of three of the thoracic legs on 

 the same side," says he found that the chrysalis had "the three limbs on one 

 side shorter than the corresponding ones on the other side." The same opera- 

 tion repeated on a somewhat younger caterpillar again showed in the chrysalis 

 three maimed limbs, " so that they could not be said to be entirely absent. These 

 results are like those of Newport ; the interpretation only was faulty, as we 

 shall attempt to prove." 



The real relations of the adult legs to the larval legs are thus 

 shown by Gonin. 



" If we carefully strip off the skin of a caterpillar near the time of 

 pupation (Fig. 608), we see that the extremity only of the legs of the 

 imago is drawn out of the larval legs ; the other parts are pressed 

 against each side of the thorax : near the ventral line a small pad 

 represents the coxa and the trochanter ; the femur and the tibia are 

 distinctly recognizable, but soldered to each other and only separated 

 by a slight furrow ; they form by their union a very acute knee or 

 bend. The femur is movable on the pad-like coxa, the tibia continues 





