VOL. XLV.J PHILOSrOPHICAL TRANSACTIONS. 505 



the air by their stigmata; and that they did not expire any of it through th^ 

 pores of their body. This paper gives an account of 36 several experiments, 

 made chief!)' with design to discover this fact, whether indeed these insects did 

 both inspire and expire the air by their stigmata, or only inspire it. These ex- 

 periments, like Mr. de Reaumur's, consist mostly in the plunging of caterpillars " 

 either into water, or some other liquor ; some also they daubed or anointed 

 over with fat and greasy substances, some quite over, and others only in some 

 places. Mr. Bonnet was inclined to think, that the small bubbles of air ob- 

 served all over their bodies, when they are immerged in water, did not come 

 from the air included within them, and which they expired by the pores ; but 

 that they were formed by the air only lodged near the surface of the skin of the 

 caterpillar, as it is about the superficies of all other bodies : he had endeavoured 

 to contrive it so, as that no air might remain thus sticking to the skin of those 

 insects on which he had made these experiments. And for this purpose, before 

 he plunged them in the water, he first washed them all over with a hair-pencil 

 or brush; and these being afterwards inmierged in the water, but very few 

 bubbles of air have been discovered on the outside of their bodies ; and fewer as 

 it appeared than Mr. de Reaumur had found on those, on which he made his 

 experiments; neither was he himself of opinion that all those bubbles which he 

 took notice of were formed by the air rushing out through the pores, but that 

 some of them were also formed by the air sticking about the exterior part of 

 the skin. 



When a caterpillar is plunged in water, one bubble of air is almost constantly 

 observed upon each of the stigmata. Mr. de Reaumur concluded, that the air 

 was not expired by these stigmata, because he could never observe that any 

 bubbles of air were ever driven out of these stigmata, as one would think there 

 must have been, if the air was really expired by these apertures. Mr. Bonnet 

 on the contrary, had seen some bubbles of air come out from these stigmata, 

 and that had contributed to make him rather think that the air inspired was 

 also discharged at the same orifices. But as these experiments are not decisive, 

 he was unwilling absolutely to determine, but proposed making more new ex- 

 periments. 



A caterpillar can remain several hours under water without perishing ; it only 

 falls into a state of numbness ; but if again taken out of the water, it is not long 

 before it again shows signs of life, and recovers. Mr. Bonnet had sought by 

 some experiments, to know if some only of these 18 stigmata of a caterpillar 

 might not be sufficient for the purposes of respiration : he has plunged some of 

 them only partially in water, sometimes by the tail, and others by the head fore- 

 most ; but always so that either two or more stigmata might be out of the water; 



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