maggot will get additional warmth from the heat of the sun, 
and is not subject to any chill, which might retard its growth, 
by the animal lying down on the damp, cold ground. 
Mr. Haines, Newport, has noticed that nearly all hides 
from yearling cattle that have died a natural death are 
covered with warbles. 
In some yearling heifers we had last spring the fly seems 
to have been very impartial, as there were as many warbles 
on the poorer heifers as on those in good condition, and in 
some cases more ; but perhaps the poorness was the effect of 
the warbles. 
Back-end calvers, that have had a summer’s run out at 
grass, are a favourite object of attack of the Warble Fly. 
Where the maggots have fallen from the backs of cattle in a 
field, it is quite a matter of course that the flies will soon 
appear to start new attacks there. 
Exposure without possibility of shelter, weakness, and 
neglect are all favourable to increase of warble attack, whether 
in old cattle or young. Under groves of trees some cattle 
were found to be quite free from attack. Where young cattle 
had sheds to run in at will during the day, and were housed 
at night, with a good feed of cake, there were seldom any 
warbles found. In places where there are large ponds, and 
the animals stand in the water during the hottest part of the 
day, the flies are not so rife, and the cattle are undisturbed by 
them. 
Many writers have asserted that it will not cross any 
extent of water. Prof. W. Fream, Downton, said that their 
cattle did not suffer much ; but there was plenty of marshy 
ground near at hand, and a good deal of timber, which afforded 
shade. Some cattle we had in a field, in which were a 
number of trees and a pond, were very little troubled by the 
Warble Fly, while some cattle in an open field close too, were 
very much tormented by them. 
Tanners have found that hides show less attack where the 
cattle have had access to water. Reaumur observes that 
Warble Plies attack cattle principally in woodland districts, 
not in the plains. 
If cattle are removed from the pasture where they 
remained in the spring during the time the maggots escaped 
