The sheep maggot-fly pest in Australia : an essay / by W.W. Froggatt, with notes and observations by W.F. Cooper.

  • Froggatt, Walter W. (Walter Wilson), 1858-1937.
Date:
[1913]
Catalogue details

Licence: In copyright

Credit: The sheep maggot-fly pest in Australia : an essay / by W.W. Froggatt, with notes and observations by W.F. Cooper. Source: Wellcome Collection.

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    rise. In England, probably only a very few flies hibernate, the great majority dying on the approach of the cold weather; and for the few living flies to multiply and increase, a fair amount of time is necessary, so that it is difficult for them to increase to such an alarming extent as in more tropical countries. Where the semi- dormant forms are more numerous, very much less time is necessary for them to increase to such an extent as to become serious ; but, in any case, every fly'- killed during the hibernating period must have a considerable effect later on, in reducing the number of flies existing during the warmer months. This has given rise to attempts to deal with the fly during the less active periods of its life. If it were possible to reduce the number of flies at this period, some diminution of the damage done by them might be attained ; at the same time, too much reliance cannot be placed upon this, for the numbers increase to an enormous extent in a very short time. Hewitt, in his study of the House-fly, expresses the belief that it is the latest, or most recently hatched forms which hibernate. Evidentl}7, either the hibernating forms are differently constituted to the ordinary forms, or else the change in climate, at the time when hibernation takes place, gives rise to a change in the fly. They become negatively heliotropic at this time of the year; that is to say, they object to light, and creep away into dark corners and crevices. During hibernation, the digestive organs shrink and occupy a very small volume of the body ; and the space which is usually occupied by the gut, is filled up with fat, upon which the flies are nourished during the winter months. In May or June, when the hibernating flies emerge (in England), there is very little fat left. Hewitt found that in some hibernating flies the ovaries were well developed, and in others they were small ; mature sperma- tozoa were found in the males. Jepson (1909 a) carried out some experiments, but they are not of much interest in connection with this particular problem. The