74? INTERNAL ANATOMY OF INSECTS. 



sal and ventral segments in the Libellulina by similar 

 ventral folds ; and in Cimbex by membranous pieces in 

 the first dorsal segment, which De Geer observed was 

 elevated and depressed at the will of the animal a . 



Air is as essential to insects in their pupa as in their 

 larva or perfect states. Lyonet, however, Musschen- 

 broek, Martinet, and* some other physiologists, have 

 doubted whether quiescent pupae breathed b ; but Reau- 

 mur and De Geer seem to have proved that they do c : 

 and if thrown into water, the same proof of respiration, 

 by the emission and retraction of a bubble of air takes 

 place, as in the larvae ; and De Geer found that if one 

 be transferred under water from one spiracle to another, 

 it will be absorbed by it d . Indeed, unless these pupae 

 had breathed, where would have been the necessity for 

 the spiracles with which all are furnished? It is remark- 

 able, however, that all these spiracles do not seem of 

 equal importance in this respect. Reaumur found that 

 if the posterior spiracles only were closed with oil, the 

 insect suffered no injury; but that if the anterior ones 

 were similarly treated, it infallibly died e . The respira- 

 tion however of pupaB seems more perfect in those that 

 have recently assumed that state, than in those that are 

 more advanced towards the imago; in which at first, from 

 Reaumur's experiments f , it appears that the posterior 

 spiracles were stopped ; and in others still older, from 

 Musschenbroek's s , even the anterior ones. Those quies- 

 cent pupae that during that state remain submerged, re- 



a De Geer ii. 946. 



b Lesser, L. i. 124. note*. Lyonet Anatom. pref. xii. De Geerii. 

 132. c lleaum. i. 399. De Geer i. 37. 



d Ibid. 40. e Reaum, i. 400. f Ibid. * De Geer ii. 129. 



