of Aquatic Respiration in Insects. 117 



and this spectacle was frequently repeated — quit its position for 

 a more desirable branch, or to take a httle swimming exercise 

 which much astonished me, and the object of which I did not at 

 first comprehend. 



In this very lively exercise, which lasted for several minutes, it 

 did not try to approach the surface or to get out of its prison. 

 Its swimming seemed rather taking pleasure, and nothing led 

 me to presume that it was struggling with the fear of drowning. 

 It was evident that this active locomotion was directed at its will. 

 It rose higher or lower, it made the round of the glass vessel, it 

 passed through the tufts of the plant, without attaching itself to 

 them. This exercise seemed an instinctive want. This wholly 

 aquatic life, the acts of which I witnessed with so much interest, 

 continued with signs of perfect health and well-being. The 

 insect was in its destined element. 



There is a singular fact, which I at first considered unimportant, 

 but which repeated observation has led me to connect with the 

 same functional object as the natatory exercise of which I have 

 just spoken. In its grave attitude of immobility, the Phj/tobius 

 from time to time agitated, almost convulsively, most frequently 

 its intermediate feet, and sometimes also the others. This vibratile 

 movement resembled St. Vitus's dance. With an excellent lens 

 I examined the body of the insect, in the hope of finding some- 

 thing analogous to a respiratory act ; but I did not perceive the 

 least atom of air. 



The fact of this normally immerged existence seemed to me 

 therefore well established. It at once calls to mind the charming 

 history which Audouin has described of the little Carabus, Tre- 

 chus [Bremus) fulvescens, which, when immersed in its retreat 

 during the whole of the high tide, nevertheless preserves its life ; 

 and also that more recently detailed in an excellent spirit of ob- 

 servation, by M. Laboulbene, relative to the mode of respiration 

 of his y^pus Robinii, under the same conditions as the Trechus 

 {Bremus) of Audouin. 



But the case of our Phytobius is otherwise surprising and 

 wholly exceptional. It has not, like the Trechus, Ramus, Me- 

 ter ocerus, &c., the resource of an impermeable down, a velvety 

 tunic which might collect and entangle a layer of air around the 

 body, for the service of the stigmata. Its tegumentary envelope 

 does not present any down under the strongest magnifier. How- 

 ever, I hasten to say that the case of its body is clothed with a 

 sort of close, perfectly impermeable, scaly covering, but which 

 does not retain the air at its surface. 



I asked myself sometimes if the Phytobius had not received 

 the faculty of suspending its respiration, of holding its breath 

 for a time, the duration of which we cannot calculate. My mind 



