LEPIDOPTERA. 265 



to descend too quickly ; it descends by stages, it stops in the air 

 when it pleases. Generally it only descends at most about one 

 foot at a time, and sometimes only half a foot or a few inches, 

 after which it makes a pause more or less long as it pleases." It 

 is in this way that the caterpillars let themselves fall from the 

 top of the highest trees. They remount again with no less ease. 



Let us listen to Reaumur's description of the means employed 

 by this caterpillar to descend from these heights. Figs. 260 and 

 261, drawn as the three preceding ones from the plates in Reau- 

 mur's Memoir, help us to follow the explanation given by the 

 illustrious naturalist of the evolutions of our little acrobat: 

 " To remount/' says Reaumur, " the caterpillar seizes the thread 

 between its jaws, as high up as it can catch it; as soon as it 

 has done this it twists its head round, lays it over on one side, and 

 continues to do so more and more every moment. Its head seems 

 to descend below the last of the scaly legs which are on the same 

 side as that to which it is inclined. The truth is, however, that 

 it is not its head which descends, the part of the thread which it 

 holds between its teeth is a fixed point for its head and for the 

 rest of its body : it is that portion of the back corresponding with 

 its scaly legs which the caterpillar twists upwards ; the consequence 

 is that it is the scaly legs and that part of the body to which they 

 belong which then ascend. When the last pair of legs are just 

 over the teeth of the caterpillar, one of its legs, viz., that which 

 is on the side towards which the head is inclined, seizes the thread 

 and brings it over to the corresponding leg on the other side, 

 which is advanced to receive it. If the head then raises itself, 

 which it will not fail to do immediately, it is in order that it may 

 seize the thread at a higher point than that at which it seized it 

 at first, or, which is the same thing, the head, and consequently 

 the whole body of the caterpillar, is found to have ascended to a 

 height equal to the length of the thread which is between the 

 place where its teeth seized it the first time and that where they 

 seized it the second time. Here then is, so to say, its first step up- 

 wards. Hardly has the caterpillar taken this than it takes a second. 

 . . . If you were to seize the caterpillar when it had arrived at 

 the end of its upward journey, you would see a packet of threads- 

 huddled together between the four hindmost of the scaly legs. 



