20 
suspect near an hundred at least are lost for one that arrives at 
the perfect state of a fly. In the first place, in the depositing 
the eggs not a little interruption is given to the female by the 
movements of the Horse : the eggs when deposited may remain 
on the hairs untouched by the animal, unless some casualty makes 
him lick those parts to which they adhere, and when ripe, or if 
hatched and opened by rain, or other moisture, the larvae may 
come forth, and crawl about till they die. 
In the mouth of the animal they have the dreadful ordeal ot 
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, on dropping from the anus 
to the ground, a dirty road or water may receive them. If on 
the commons, they are in danger of being crushed to death, 01 
of being picked up by the birds, who so frequently for food attend 
the footsteps of the cattle. By such contingencies as these. 
Providence has wisely prevented their too great increase, and the 
total destruction of the animals they feed on. 
The egg is glued on the hair with the broad end downwaid, 
(see fig. 2, 3,) and is thus well disposed for the operation of the 
tongue in removing the operculum. This operculum is of an 
oval figure, surrounded with a prominent margin. The micro¬ 
scope shews the case of the egg to be shagreened in squares, or 
divided by lines longitudinally and transversely disposed. 
Of the Larva or Grub of the Oestrus Equi, or spotted Horse Bot. 
At its first hatching it is, as we have observed, a small active 
worm, long in proportion to its thickness, but as its growth ad¬ 
vances, it becomes proportionably thicker and broader, and 
beset with bristles. 
Some of these Larva?, when about two-thirds grown, are 
represented in Plate I. fig. 5, adhering to the stomach. They are 
