330 
The Warble-flies of Cattle 
eggs on the skin of the back. She advocated, as a most important preventive 
measure, the smearing of the backs of cattle during the fly season to prevent ovi- 
position. The discoveries of 1892 threw an entirely different light on the matter. 
An anonymous correspondent 1 communicated to Riley a very complete account 
of the oviposition of H. lineatum in Texas. There the fly was known as the 
“heel-fly” from its habit of attacking the lower part of the legs of standing 
cattle, but the actual process of oviposition was studied in the case of an old 
and feeble animal, incapable of gadding to take refuge in the water. Lying 
helpless on the ground, it was entirely at the mercy of the warble-flies, and 
during the first few days of March it was seen to be attacked by about fifty flies. 
“ The flies were observed to approach very swiftly and deposit their eggs any¬ 
where on the sides, belly, or tail, near the anus, and on the front legs. The 
flies were left unmolested in many cases until, after remaining on or about 
the animal from five to ten minutes, they flew off. The eggs were then found 
without difficulty, usually placed four or six together, and fastened to a hair.’" 
Had wen also observed the oviposition of H. lineatum in 1915. We quote the 
most important passages of his account: 
On four occasions H. lineatum has been captured by hand on recumbent animals, two 
by myself and two by my cowman. Each time the fly was resting or ovipositing on the fore¬ 
foot, which was tucked in under the elbow. When ovipositing, the fly backed up and pushed 
its ovipositor under the hairs. Numerous eggs were found on this part of the animal, i.e. the 
side of the sternum beneath the elbow—so this seems a favourite spot for egg-laying. On 
May 2, while watching for flies, I observed one sitting on the ground just behind, and a few 
inches from the heel of a young heifer. While watching I saw it run backwards like a crab, 
reach upwards from the ground and oviposit on the hair which hangs down round the 
coronet. The attitude was reminiscent of the way in which a scorpion curls up its tail.... It 
seems that this site also is a favourite one for oviposition. On May 3... a fly was observed 
on the ground near a recumbent cow; this insect ran backwards. .. and oviposited about 
six inches below the point of the ischium, where the cow’s body touched the ground. From 
this point it laid eggs at intervals all along the side touching the ground, as far forward 
as the elbow, without touching the animal except with its ovipositor... .Numerous eggs 
have been found also between the point of the hock and the ischium, also on the inside of 
the legs. On one occasion seven eggs were found on the scrotum of a bull-calf, and at other 
times they have been encountered on the tail. From these observations it is evident that 
H. lineatum lays its eggs principally when an animal is lying down, and that it does so 
standing on the ground, thus giving the animal a minimum amount of irritation... .The 
position of H. lineatum when ovipositing is always such that its head points in the same 
direction as the hairs. 
In the case of H. bovis, oviposition was first noted by Carpenter and Steen 
in 1907, but the account is meagre and is chiefly important from the statement 
that the eggs are chiefly laid on the legs. “ The fly strikes both at the fore and 
hind limbs, near the hock, more rarely on the shoulder.” 
A fuller account was given by Hadwen (1912). ‘'When 4 warble-fly 
(H. bovis) strikes, it hangs on for a second, evidently holding on with \ts legs 
while it fits on an egg.” 
1 Now known to be a Mr Schaupp to whom the credit of this important discovery ought to 
be attributed. 
