66 
HORSE. 
The two wings are moderately large, closed together when at rest, 
hyaline, sometimes opaque white; with a transverse brown or grey 
band and two spots, or a slight marking at the tip. The legs are long 
in proportion, smooth and mostly yellowish brown. The fly is known 
by the various names of the Great Spotted “Horse Bot Fly”; the 
“ Horse Bee ” ; and also, from one of the places it selects for egg-laying, 
as the “ Knee Bot Fly.” 
In Europe the fly is to be found from June or July until October. 
It is of some interest to note that, in the observations of the veterinary 
surgeon of Cape Colony, the time of the deposit of the eggs varies 
from what it is here correspondingly with the different time of year of 
the summer season in that part of the world. He found egg-laying to 
begin about the beginning of January, and to continue until about the 
end of April. 
The eggs are hardly the twelfth of an inch long, white, spindle- 
shaped at one end, and obliquely truncate at the other, and are 
attached by the female Bot Fly to the hairs of the Horse. The hair of 
the mane, the shoulders, and the inside of the knee, are places especially 
chosen for egg-laying. 
The method of deposit is for the fly to poise near the 
Horse, and then flying at the spot to leave the egg fixed to 
the hair by a glutinous moisture, and so to continue until 
four or five hundred eggs may be laid on one animal. Her 
whole supply is stated to be as much as seven hundred. 
These eggs are ready to hatch in a period variously 
stated as from about five days to three weeks, but the 
maggot which then emerges is not at first of the shape 
figured (p. 65), which it gradually grows to, but very much 
narrower in proportion, more like a short worm, smallest 
at the tail end and gradually increasing in width till about 
the fourth ring from the head, or anterior extremity, and 
then quickly lessening again. How these maggots are 
conveyed into the Horse does not appear to be an absolutely 
settled thing; some may possibly creep through the hair to 
the mouth. The most commonly received opinion how¬ 
ever, is, as given by Dr. Cobbold and others, that the 
moisture and warmth from the Horse’s tongue when he licks the spots 
where the eggs are attached hatches them, or, rather, helps to free the 
maggot if near hatching time, and the maggot being produced adheres 
to the Horse’s tongue. Thus some amount of larvae from the many 
eggs laid are conveyed into the mouth whence they pass downwards, 
or are carried downwards with food, &c., from the mouth to the 
stomach. 
On the above points I was favoured with the following practical 
EggsofHorse 
Bot Fly, nat. 
size and mag¬ 
nified, after 
Bracy Clark. 
