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of fruit trees, and there brought to perfeAion for the confen'ation of 

 its fpecies, otherwife (as before mentioned) it would be devoured by 

 pifmires or birds : and it mxilt aUb be obfersed, that thefe creatures 

 have no ability of fceking their food at a dillancc. 



Befides what I have mentioned, I had others of thefe cryfales, 

 which I kept in my ftudy to vsatch their transformation, placing them 

 in a glafs, fo as to give them a fupply of air; but I never could per- 

 ceive the leaft appearance of any evaporation from them, though, as 

 foon as they were converted into living animals, fo great a quantity of 

 moifture iflued from their bodies as to hinder their moving, and often 

 to occafion their fi:icking on their backs to the glafs, which made it 

 neceflary for me to give them more room : here is to be noted how 

 wonderfully compact muft be the fkin of the crylalis, fo as to fuffer 

 no evaporation of its moitiure, left the animal within fhould be injured 

 by the want of it ; and this is another inftance of the inconceivable 

 correctnefs of Nature in her works. 



Finding myfelf miftaken in opinion, refpeAing^ the black Flies de- 

 pofiting Maggots in the bloflbms, I determined, if polTible, to exa- 

 mine the nature of their propagation, and the rather as I alTured my- 

 felf that they muft be produced by cryfales. I therefore opened fome 

 of thefe black Flies, and I can fafely fey that, from a rough calcula- 

 tion, I found in each female three hundred eggs. 



Going into my garden in the morning, to take fome of thefe Flies, 

 that I might confine them till they laid their eggs, and I might dif- 

 cover what kind of cryfales would be thence produced, I perceived 

 the Flies fitting on the leaves and flowers as immoveable as if they 

 were dead, and even, upon a gentle touch of the branches, to fall 

 to the ground ; whereas all other Flies, in warm weather, are very 

 nimble. Hereupon it occurred to me that, when the wind blows 

 from the North, Flies do not rove about in the air, but lit upon the 

 trees, where we obferve them in greater numbers than when the 

 air is warm ; and as in cold and cloudy weather they fettle in great 

 numbers, not in the fummits of trees, but in the lower branches, 



