230 
ANIMAL INTELLIGENCE. 
sembles analogous instances which have been mentioned 
in the case of spiders. 
Dipterous Insects . 
The gad-fly, whose eggs are hatched out in the intes- 
tines of the horse, exhibits a singular refinement of instinct 
in depositing them upon those parts of the horse which 
the animal is most likely to lick. For, according to 
Bingley and other writers, 4 the inside of the knee is the 
part on which these flies principally deposit their eggs ; 
and next to this they fix them upon the sides, and the 
back part of the shoulder; but almost always in places 
liable to be licked by the tongue.’ The female fly deposits 
her eggs while on the wing, or at least scarcely appears to 
settle when she extends her ovipositor to touch the horse. 
She lays only a single egg at a time — hying away a short 
distance after having deposited one in order to prepare 
another, and so on. 
The following anecdote, which I quote from Jesse, 
seems to indicate no small degree of intelligence on the 
part of the common house-fly— intelligence, for instance, 
the same both in kind and degree as that which was dis- 
played by Sir John Lubbock’s pet wasp already mentioned : 
Slingsby, the celebrated opera dancer, resided in the large 
house in Cross-deep, Twickenham, next to Sir Wathen Waller’s, 
looking down the river. He was fond of the study of natural 
history, and particularly of insects, and he once tried to tame 
some house-flies, and preserve them in a state of activity through 
the winter. For this purpose, quite at the latter end of autumn, 
and when they were becoming almost helpless, he selected four 
from off his breakfast-table, put them upon a large handful of 
cotton, and placed it in one corner of the window nearest the 
fireplace. Hot long afterwards the weather became so cold 
that all flies disappeared except these four, which constantly 
left their bed of cotton at his breakfast-time, came and fed at 
the table, and then returned to their home. This continued 
for a short time, when three of them became lifeless in theii 
shelter, and only one came down. This one Slingsby had 
trained to feed upon his thumb-nail, by placing on it some moist 
sugar mixed with a little butter. Although there had been at 
intervals several days of sharp frost, the fly never missed taking 
his daily meal in this way till after Christmas, when, his kind 
