216 PTILOTA, 



Reaumur was enable by experiments with chrysalides to 

 abridge or extend their lethargic state by artificial heat 

 or cold ; the chrysalides of various lepidopterous insects, 

 which would not ordinarily be produced until spring, being 

 placed in a hot-house, and the butterflies being developed in 

 the middle of the winter, — the contrary effects being produced 

 when they were placed in an ice-house. Hence it is evident 

 that by the action of an increased temperature a certain 

 evaporation of the fluid matter, with which the newly-formed 

 chrysalis is filled, takes place; but I can by no means 

 agree with Kirby and Spence, that " this necessary trans- 

 piration, other circumstances being alike, must take place 

 sooner in a small than in a large pupa ;" and, consequently, 

 " that small pupse continue in that state a shorter time than 

 those of larger size :" indeed, I am disposed to question 

 the correctness of the latter assertion, and to say, on the 

 other hand, that the duration of the pupa state is totally 

 independent of size. I might adduce hundreds of examples 

 in support of this assertion, but it T^dll be sufficient to 

 observe that the largest lepidopterous insect, the great 

 Death's-head moth, requires, according to Haworth, but 

 one month at the end of autumn, when the vv^eather has 

 been comparatively cold, to undergo its pupa state. If eva- 

 poration were the sole operation to which the pupa was sub- 

 ject, there would be sufficient grounds for the theory of eva- 

 poration entertained by Swammerdam, Reaumur, Kirby, and 

 Spence; but such is not the case, for Reaumur having 

 inclosed a pupa in a stopped glass tube, collected only seve- 

 ral drops of water, v.iiich were condensed against the sides of 

 the tube, the pupa having lost only one eighteenth part of 

 its original weight. Hence the developement of the organs 

 of the inclosed animal, by absorption and assimilation, con- 

 stitutes the great operation whicli the pupa has to undergo, 

 and this must, of course, be of equal duration, whether the 



