523 THE GAD FLY. 



■where they can find fultable food, and neceffary warmth* 

 The young of certain flies are only capable of fubfifling 

 below ground, and of deriving food from a certain flower, 

 the narcilTus. The mothers of thefe depofit their eggs in 

 the roots of that plant. Other flies enter the anus of a 

 horfe, becaufe their young are only capable of fubfifting 

 in the entrails of that animal, where they remain till 

 they are about to be metamorphofed, and are then ejefl- 

 ed with the dung *. Others are provided with a curious 

 inllrument, by which they perforate the hides of cattle ; 

 and in each hole thus made, they depofit an egg. 



Each of thefe worms, after being hatched, finds itfclf 

 furrounded with its proper food, among which it grows ; 

 and the cell increafes in fize at the fame time, till it 

 fometimes reaches the bulk of an egg. The wound be- 

 comes filled with purulent matter ; and the opening 

 from which it runs ferves to fupply the infe£t with air. 

 After the worm has grown there to its full fize, it needs 

 a place more dry, and of lefs heat, for its metamorphofis ; 

 it then drops from the orifice of the wound, and betakes 

 itfelf to foaie hole, or other retreat, where it is tranf- 

 formed. 



An infl;In£l as Angular as any of the former is that by 

 which fonie flies are direcled to the nofe of a flicep, a 

 goat, or a deer, to lay its eggs. It is in the frontal finus 

 of thefe large animals, that the worms produced by thefe 

 eggs are deilined to fcarch for ,the only food capable of 

 fupporting them. Some of thefe worms, after being 

 ejected fi'om this (Irange nidus, become covered with a 

 hard fliell, in which their lafl: change is completed. Na- 

 ture, which provides for every exigence, has furnilhed 



this 



* Reaumur, Tonic IV. Mem. xll^ 



