THE CATERPILLAR. 55 



lars ; they appear at first view to be hollow car- 

 tilaginous tubes, and of the colour of mother-of- 

 pearl. These tubes are often seen to unite with 

 each other ; some are perceived to open into the 

 intestines, and some go to different parts of the 

 surface of the body. That these vessels serve to 

 convey the air, appears evidently from the famous 

 experiment of Malpighi ; who, by stopping up 

 the mouths of the stigmata with oil, quickly suf- 

 focated the animal, which was seen to die con- 

 vulsed the instant after. In order to ascertain 

 his theory, he rubbed oil upon other parts of the 

 insect's body, leaving the stigmata free ; and this 

 seemed to have no effect upon the animal's health, 

 but it continued to move and eat as usual : he 

 rubbed oil on the stigmata of one side, and the 

 animal underwent a partial convulsion, but re- 

 covered soon after. However, it ought to be ob- 

 served, that air is not so necessary to these as to 

 the nobler ranks of animals, since caterpillars will 

 live in an exhausted receiver for several days to- 

 gether ; and though they seem dead at the bot- 

 tom, yet, when taken out, recover, and resume 

 their former vivacity. 



If the caterpillar be cut open longitudinally 

 along the back, its intestines will be perceived 

 running directly in a straight line from the mouth 

 to the anus. They resemble a number of small 

 bags opening into each other, and strengthened 

 on both sides by a fleshy cord, by which they are 

 united. These insects are, upon many occasions, 

 seen to cast forth the internal coat of their intes- 

 tines with their food, in the changes which they 



