44 
extremity of the rectum, and should be removed by the fingers. 
The destruction of a single one at this season of the year is not 
only the death of an individual and its effects, but the almost 
certain destruction of a numerous progeny ; it is also useful in i 
preventing the irritation which the spines of the Bot occasion, to 
the anus, which irritation becomes very distressing to the ani¬ 
mal if he is used op the road, occasions him to move awkwardly, 
wriggle himself about, and to be sluggish, and though beaten 
severely he spon relapses again into his awkward manner of going ; 
which as this happens generally jm warm weather, is most com¬ 
monly attributed to mere laziness. 
Some further remarks on their probable effects we leave till we 
treat of the Cuticolar and Cavicolar Oestri. 
* * Second family, CuticoLjE. 
The Oestrus Bovis, or Gad Fly. 
Of all the European species of this genus, this is the largest, 
and is not unfrequently seen in country situations in the backs of 
oxen and cows. They form tumors as large as pullets eggs on 
the sides, about the back and loins. See their appearance, Plate 
II. fig. 2, a the tumor or abscess, b the external opening. With 
us among the country people they are called Warbles, Wornils, 
Wormuls, and sometimes Bots. 
When I first took up the investigation of these animals, I was 
in considerable perplexity what this species could be, since I 
possessed the Oestrus Bovis of Linnaeus, agreeing perfectly with 
the description, and which was a Horse Bot ; nor had I then 
seen the writings of Vallisneri or Reaumur, which, as Linnaeus 
had seen and referred to, I did not suppose could have fallen into 
such an error as to have omitted entirely this remarkable species, 
or have confounded it with the Equi, but it so proved, and on 
obtaining the perfect insect from the back of the cow, the mys- 
