( 18-7 ) 



in Tome fort tranfparent, like a piece of horn or tortoife-lliell, feeii 

 with the naked eye, and at Q and T, are fhewn the organs, by the 

 help of %\ hich the animal can run along the fniooth furface of the 

 glafs, and alfo hang to it a whole night. The formation of thefe 

 organs is very wonderful, for all thofe parts with which they are 

 covered, and which one would conclude to be hairs, are fo exacflly 

 and regularly floped off, and particularly of fuch regular lengths, as 

 if they had been all clipped with fcilfars, that when the animal 

 places its foot any where^ they all touch the place at the fame time, 

 and what is more, all thefe particles, which feem to the eye to be 

 hairs, have at their extremities a hook, and, at a little diftance 

 from tlrence, two other hooks ; but by reafon of their extreme mi- 

 nutenefs, though the limner eonfefled he faw them through the mi- 

 crofcope> he declared he could not reprefent them in the drawing. 



Now if we confider, what I have always experienced, that a 

 glafs, though wafhed ever fo clean, will have many particles ad- 

 hering to it, tliough thele are fo fmall, that the claws on the feet of 

 fmall tlying infects cannot take hold of them, we may eafily con- 

 ceive that thefe minute hooks, may take hold of the fmall particles 

 of water or motes from the air adhering to the glafs. And here 

 we may difcover the error of thofe who formerly fuppofed there 

 were cavities in glafs, wherein Flies could fix their claws and 

 climb up. 



In the fpring feafon I obferved, on feveral parts of my apple trees, 

 many caterpillars gathered together, which, in moving from place 

 to place, fattened themfelves by a kind of thread, and I began to 

 confider, whether thefe were produced by the black Flies, and it 

 feems they are called by gardeners de IFolf. To fatisfy myfelf in 

 this refpeel:, I cut off from the apple tree, two branches, on which 

 were thefe caterpillars, placing the ends cut off in a veflel of ^^•a- 

 ter in my hall, in order that the leaves might remain freih, and 

 xafibrd nouriftiment to the caterpillars : w*hen the leaves began to 



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