4 58 
GAD-FLY. 
taken up by accident, it may pass on to the intesti- 
nal canal before it hatches ; in which case its ex- 
istence to the full growth is more precarious, and 
certainly not so agreeable, as it is exposed to the 
bitterness of the bile. 
“ I have often with a pair of scissars clipped off 
some hairs with eggs on them from the horse, and 
on placing them in the hand, moistened with saliva, 
they have hatched in a few seconds. At other 
times, when not perfectly ripe, the larva would not 
appear, though held in the hand under the same 
circumstances, for several hours ; a sufficient proof 
that the eggs themselves are not conveyed to the 
stomach. It is fortunate for the animal infested by 
these insects that their numbers are limited by the 
hazards they are exposed to. I should suspect near 
a hundred are lost for one that arrives at the perfect 
state of a fly. The eggs, in the first place, when 
ripe, often hatch of themselves, and the larva, with- 
out a nidus, crawls about till it dies ; others are 
washed off by the water, or are hatched by the sun 
and moisture, thus supplied together. When in 
the mouth of the animal, they have the dreadful 
ordeal of the teeth and mastication to pass through. 
On their arrival at the stomach, they may pass 
mixed with the mass of food, into the intestines ; 
and when full grown, in dropping from the animal 
to the ground, a dirty road or water may receive 
them. If on the commons, they are in danger of 
being crushed to death, or of being picked up by 
the birds who so constantly attend the foot-steps of 
