328 
The Warble-flies of Cattle 
N. American cases, was in reality H. lineatum. The history of the recognition 
of this species is curious. In 1875 Brauer received from Colorado larvae taken 
from a bison which he recognised as different from H. bovis, and which he 
named H. bonassi. In 1888 Handlirsch captured some Hyjpoderma flies which 
were not bovis in a field where cattle were pastured, and the following year he, 
in company with Brauer, found a pupa, corresponding exactly with his bonassi 
larva, from which he bred the same fly, of which the normal host was as yet 
uncertain. The matter was settled by Brauer in 1890, when the fly was proved 
to be a cattle parasite and was found to be the one described by de A illers as 
early as 1789 under the name of Oestrus lineatus, of which the bionomics were 
hitherto quite unknown. Clark seems to have met with it but to have had 
great doubts as to its identity, as at different dates he named it Oestrus 
haemorrhoidalis var. (1797), Oestrus bovis $ var. j8 vernalis (1815), and later, 
following Leach (1817), Oestrus ericetorum. 
Since 1890, therefore, it has been clearly realised that there are two ox 
warble-flies, H. bovis and H. lineatum, both of which occur, though very un¬ 
equally, in all the countries from which warble attack has been reported. 
The comparative poverty of these flies in entomological collections is largely 
to be accounted for by their habits. Though the fly season may, by the occur¬ 
rence of early and late examples, be fairly long, the period during which they 
are at all plentiful in any district is quite brief, and individual flies are believed 
to have a very short life. Hadwen (1914-15) twice observed H. bovis, which 
had been captured without injury a few minutes previously, and which had 
been placed on a calf’s back with a net over it to prevent escape, to be seized 
with a sudden spasm and to die instantaneously. He found the flies very 
intolerant of captivity. In large cages they quickly batter themselves to 
pieces, and in small cages Hadwen did not succeed in keeping them alive more 
than a few hours. Carpenter (1914) also observes that unless transferred at 
once to a cage in a dark place they damage themselves badly, and that this 
is especially true of the males. 
The fact that H. bovis, at all events, is never on the wing except in sunny 
weather further militates against its capture by entomologists. Moreover both 
species are very rapid fliers and not easily taken in the open. Nevertheless it 
is clear that on occasion they may occur plentifully enough, for Riley states 
that during the first few days of March 1892 in Texas “an old and feeble 
animal, which had laid down and had not strength to rise, was observed to 
be attacked by about fifty flies, of which upwards of a dozen were captured. 
It has often been remarked, and it was confirmed in these Texas observations 
that the flies will not venture over water, and while H. lineatum was about 
“the cattle on clear days came to the river about 9 o’clock in the morning, 
and remained standing in the middle of the river until 5 o’clock in the after¬ 
noon. ... Most of the cattle stood on flat rocks protruding out of the water, 
so that no part of their body or legs were submerged; but in spite of this fact, 
while they were standing in the river they were unmolested.” 
