L17.] 
143 
subulated wings, abounding in every nest ; and are liatclied by 
the warmth of the bird's own body during incubation, and 
crawl about under its feathers. 
A species of them is familiar to horsemen in the south of 
England under the name of forest-fly ; and to some of side-fly, 
from its running sideways like a crab. It creeps under the 
tails, and about the groins, of horses, which at their first coming 
out of the north, are rendered half frantic by the tickling sen- 
sation ; while our own breed little regards them. 
The curious Eeaumur discovered the large eggs, or rather 
pupce, of these flies as big as the flies themselves, which he 
hatched in his own bosom. Any person that will take the 
trouble to examine the old nests of either species of swallows 
may find in them the black shining cases or skins of the 2^W^ 
of these insects : but for other particulars, too long for this 
place, we refer the reader to "I/Histoire d'Insects" of that 
admirable entomologist — torn. iv. pi. 11. 
Selborne, July 8, 1773. 
LETTER LIV. 
TO THOMAS PENNANT, ESQ. 
As you desire me to send you such observations as may occur, 
I take the liberty of making the following remarks, that you 
may, according as you think me right or wrong, admit or reject 
what I here advance, in your intended new edition of the 
" British Zoology." 
The osprey was shot about a year ago at Erinsham pond, a 
great lake, about six miles from hence, while it was sitting 
on the handle of a plough and devouring a fish : it used to pre- 
cipitate itself into the water, and so take its prey by surprise. 
A great ash-coloured butcher-bird was shot last winter in 
Tisted Park, and a red-backed butcher-bird at Selborne : they 
are rarce arcs in this county. 
