520 PHILOSOPHICAI. TRANSACTIONS. [aNNO 1700. 



nations, the point or centre being fixed between their wings. The great sort 

 of libella are generated under water, wrapped up in a membrane, which at length 

 dissolves. 



When the young libella is ready to quit its case, it dilates its belly, that the 

 water may enter at the anus into the intestines, then it compresses itself, to 

 circulate the water, which it expels and shoots out a great way ; it receives more 

 water into its intestines, and ejects after the same manner. It continues this 

 action with great force for some time, and makes the water circulate in the 

 vessel, all which motions may be compared to the breathing or panting of a 

 horse who has been run hard. 



To satisfy myself that it took in the water at the anus, and not at the mouth, 

 I put a libella upon my finger, which I held fast by the legs, and dipped it under 

 water, with its head downwards, the anus being even with the water, so that it 

 might get into the intestines, which it cast out a good way: I then drew my 

 finger a little further out, so that the water could not enter at the anus, the fly 

 continued its motion, but ejected no water. My opinion is, the animal does 

 this in order to cleanse its body from all excrements in that element, where it 

 leaves its old robes, to appear in a more glorious and new form in the open air. 



There are a great number of small vessels which closely unite the body of the 

 libella to its case ; it is necessary that these be dry, that they may the sooner 

 break when it makes its efforts to get out of its case, which cannot be done 

 as long as there is any aliment in the intestine to afford nourishment to the case 

 and its strings ; and perhaps this is the reason why no insects will take any food 

 when they are going to change their forms ; and if they do not cleanse them- 

 selves as the libella do, yet they stay a great while longer before they change 

 without any aliment ; the libella is not longer than half a day in quitting its 

 case and taking its flight. 



It is wonderful how this insect cuts the air, making a thousand whirlings with 

 extraordinary quickness. To know the cause, we must cut the skin of the libella, 

 which is very fine all along the back, and be sure to bear the point of the scis- 

 sars upwards, lest we cut the interior parts. We must also draw the skin to 

 the right and left hand, and fix it with pins on a table, that we may discover 

 the sixteen muscles which lie between the wings and the legs, eight on each 

 side, of the thickness, length, colour, and almost figure or shape of a grain of 

 barley, contiguous to one another, and without adherence. We may observe 

 that each muscle is composed of many fleshy fibres, which do not seem to be 

 joined together, but terminate round at the ends of the muscle, where they 

 compose a common tendon, so that one might discern any of these fibres to be 

 a small muscle, of which the chief muscle is composed. 



