OF MUSCULAR MOTION. 4(51 



from the rest with respect to their flying apparatus, by being deficient 

 in posterior wings, instead of which they possess balancers. We have 

 before ( 168) expressed our opinion of their supplying the place of 

 posterior wings ; modern experiments have confirmed this opinion in as 

 fur as they anatomically agree with the wings, namely, in consisting of a 

 simple but somewhat more compact neurated membrane, which, as well 

 as the membrane of the wing, is a continuation of the epidermis, and 

 forms a closed, and, in these, a smaller pedunculated bag. Into this 

 peduncle a tolerably thick trachea passes, but which, however, is not 

 more than half as thick as the foot-stalk, and Avhich, as soon as it 

 reaches the knob, ramifies within it in many branches. With respect 

 to the function of this poiser during flight, Schelver* has already 

 proved that they are essential to it. He cut off the balancers of 

 several Dipt era ; they indeed still flew, but only short distances. I 

 have convinced myself of the correctness of his assertions by many 

 experiments : every fly which was deprived of these organs had lost 

 the art of flight ; they indeed flew a distance of from one to two feet, 

 but then rolled over, and fell to the ground. If then they were 

 urged, they made a fresh endeavour to fly, but which again failed in the 

 same way, as well as in all subsequent ones. To convince myself if 

 any other mutilation of the body would affect the capacity of flight, I 

 now likewise cut off the scales, but the result did not justify my 

 expectations. Erislalis tenax flew with the same rapidity and skill 

 after as before the operation, the same as if it had suffered no loss. 

 Schelver, indeed f, gives a different result to the same experiment, but 

 he errs ; I have frequently repeated my experiment, and always with 

 the same consequence. The results to the capacity of flight from the 

 loss of the legs are also not correct, for a Tipula, from which I removed 

 every leg but one, flew as well as before the experiment, but the loss 

 of all the legs appears to injure that operation. 



267. 



Having thus explained the different motions of insects, we still have 

 to make a few general observations upon the force and duration of 

 muscular motion. Both attain a degree in insects which remain to be 



* Beobacktungen iibcr den Fluguncl das Jesumme einiger Zwciflugligcn Insckten. 

 Wiedemann's Arcliiv. vol. ii. Pt. 2, p. 212. 

 f Ib. No. 4. 



