42 
used to make the eggs adhere to the hair or to the skin ; they are 
one millimetre and a quarter long (that is to say, rather more than 
half a line in length). 
With regard to the method of egg-laying, it is stated (see work 
quoted below, p. 50) that when the fly is about to deposit its 
eggs it flutters over the back of the ox for a minute or two, then 
suddenly drops, deposits an egg on the skin, rises in the air, again 
flutters, descends with the like rapidity as before, and drops another 
egg,—and that this performance is repeated ten or twelve times in 
half an hour. In the same work an instance is given where, on 
alarm having been caused by a Warble Fly, the insect was captured 
in the very act of laying, with the egg still in the pincers of its 
ovipositor, and was identified by Dr. Brauer as the female of the 
Hypo derma bovis. 
The point of where the egg is deposited is very important for 
practical considerations, and there has been a great deal of very 
vague speculation on the matter, but we know as matter of proof * 
that the ovipositor is not suited for purposes of boring, also that 
in the different directions of the microscopic channel communicating 
between the embryo larva beneath the hide with the minute orifice , 
on the surface, the channel is to be found so curved that it could not 
possibly have been formed by the ovipositor having been inserted. 
In the course of my own examinations, by making sections of 
hide in the early stage of infestation, I was able to trace the 
course of the maggot channels (then no wider than a hair passing 
from the minute then bloody maggot cell beneath the surface) by 
giving a light pressure. Thus the blood pressed along the gallery 
marked its course until it appeared as a very little speck on the 
outside of the hide, showing the course of the channel clearly. 
The channels (of course, as examined microscopically) were not a 
smooth boring, but merely a passage, apparently gnawed or torn by 
the mouth forks of the young maggot, and varied in direction. 
They were sometimes slanting, or taking a straight course; or 
again, so completely curved at the upper part (going a little way 
along just under the cuticle, and then turning and going right 
down to the embryo maggot-cell just below the hide), that it 
appeared impossible in any case, and demonstrably so with regard 
to the curved channel, that the passage could have been formed by 
the perforation of the telescope-jointed ovipositor,* set with a row 
of hairs or bristles standing forward on the edge of each of the 
fc. 
* See much magnified figure, ‘Parasites and Parasitic Disease,’ p. 49, re¬ 
ferred to, ante, p. 41. 
