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I do not find this to be the case, or at least only by accident ; 
for when they have remained on the hairs four or five days they 
become ripe, after which time the slightest application of warmth 
and moisture is sufficient to bring forth in an instant the latent 
larva. At this time, if the tongue of the horse touches the eiw 
its operculum, is thrown open, and a small active worm is produced, 
which readily adheres to the moist surface of the tongue, and is 
from thence conveyed with the food to the stomach. If the egg 
itself be taken up by accident, it may pass on to the intestinal 
canal before it hatches ; in which case its existence 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 had proof of 
this by making the following experiment with the eggs. 
With a pair of scissars I clipped off some hairs with the eggs 
on them from the horse, and on placing them in the hand, moist¬ 
ened 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 con¬ 
veyed to the stomach. See fig. 4. 
It is worthy of remark, that it is probable the greater part of 
the ova deposited by this fly, are taken up in consequence of the 
irritations of other flies, as the Canopes, Tabani, and Muscce, who, 
by perpetually settling on the skin, occasion a horse to lick him¬ 
self in those parts, and thus receive the larvae on the tongue and 
lips ; and a horse that has had no ova deposited on him, may 
yet have the Bots, by performing the friendly office of licking 
another horse that has. The eggs on the shoulder are particu¬ 
larly well disposed for being received in this way. 
It is fortunate for the animals infested by these Insects, or 
rather most beautifully ordained, that their numbers are much 
reduced, and kept within due limits, by the hazards they are 
exposed to in the singular round of their propagation. I should 
