PREVENTIVE MEDICINE 349 



day suffer most. Prevention should aim at the destruction of the 

 flies and keeping the sheep as clean as possible so that they are less 

 attractive to the flies. Destruction of the flies may be effected 

 by destroying the larvae or maggots before they drop off the sheep 

 to pupate. Burying or otherwise destroying the carcases of sheep 

 and all other animals, including rabbits and birds, will do much 

 to keep down this pest by denying them suitable egg-depositing 

 places, but a very good method is to provide " traps " in the form of 

 carrion, such as dead rabbits, &c., on which the flies may lay their 

 eggs and which are collected and destroyed. Sheep should be 

 inspected daily during the blow-fly season. Maggots must be 

 removed and destroyed, not merely scraped off and allowed to drop 

 on to the ground. Soiled fleece should be cut away from the anal 

 region, and sheep dogs should be kept clean. Suitable antiseptic 

 ointments help to ward off further attacks, and wounds on all 

 animals require appropriate surgical treatment. Brown* suggests 

 the destruction of flies by the liberation of poison gas, the sheep 

 being removed meanwhile to higher ground. Brown points out that 

 cross-bred sheep and those with light dry wool are not so often 

 attacked by the fly as are merino sheep, in which the wool is 

 dense and greasy. A thorough washing of sheep at the beginning of 

 summer removes the dirt and grease from the wool which is so 

 attractive to the fly, and it is well known that dipping lessens the risk 

 of " strike," the cleaner the dip leaves the sheep the greater is the 

 protection. Sulphur dips are especially useful for this purpose. In 

 some localities the sheep are collected in the early morning while 

 the fleeces are still wet with dew ; dry powdered arsenic dip is dusted 

 into the fleece along the back and around the hindquarters. It is 

 said that this affords protection for about a week or ten days, unless 

 rain washes it off. 



SHEEP KEDS. 



The sheep ked, Melophagus ovinus, one of the Hippoboscidce, 

 sometimes miscalled a " tick," is a true six-legged fly, although 

 without wings. Its life-cycle is completed on one host, the sheep. 

 The adult ked clings to the wool of the sheep with its clawed feet 

 and lays, not eggs, but fully developed larvae. The outer covering 

 of the newly laid larva soon hardens to form a pupa case, within 

 which the ked matures. The female is said to produce five or more 

 young successively.! Keds may move from shorn sheep on to 



* Queensland Agric. Journ., 1917, Vol. VII., p. 85, through Vet. Rev., 1917, 



Vol. I., p. 456. 

 f Leaflet, No. 74, Dep. Agric. Tech. Inst., Ireland. 



