16Q 



dangerous, owing to the fact that various bacteria can pass through 

 the ahmentary tract of the insects without destruction and can thus 

 be deposited on the food. Cases of intestinal myiasis by flies of this 

 group are rare, but cases in man of nasal or auricular myiasis have 

 been recorded. 



C. macellaria causes considerable losses on ranches in west Texas, 

 New Mexico and Arizona. Injury to sheep in west Texas is caused 

 by species of Lucilia, and during the winter, infestation by Phmmia 

 regina of wounds resulting from dehorning, castration and branding, 

 may occur. Investigations indicate that all cases of myiasis in animals 

 during summer and autumn are due to C. macellaria, which has the 

 effect of causing owners to reduce the size of their herds, especially 

 during the fly season. The screw worm has developed a tendency to 

 attack living animals and, when flies are numerous, the slightest 

 wound becomes a site for entrance. Live-stock are therefore not 

 branded after 1st May or before 1st November, while dehorning, etc., is 

 performed during the winter months. Any animal giving birth to young 

 during the summer is likely to become infested, and calves are often 

 injured in the mouth, causing the loss of teeth. Infestation in pigs 

 occurs in the ears as the result of wounds caused in fighting. Infestation 

 of sheep, goats and dogs may occur on any part of the body. A 

 frequent source of infestation results from the presence of ticks ; 

 live-stock attacked by horn flies, stable flies or Tabanids invariably 

 develop cases of screw- worm. 



The question of the relationship of meat-infesting flies to disease 

 transmission is deserving of more extended investigation. Some 

 connection exists between carcase-infesting flies and the so-called 

 Hmberneck in fowls. The latter have been observed to become 

 partially paralysed and die from eating maggots and decaying 

 animal matter. Dr. E. W. Saunders, of St. Louis, believes that 

 there is some connection between limberneck in fowls and polio- 

 myelitis in man, and that certain species of blow-flies are respon- 

 sible for the transmission of the disease. Observations on the 

 habits of meat-infesting flies, particularly C macellaria, suggest the 

 possibility of a connection between the flies and the transmission of 

 anthrax among live-stock in Texas. Infection may be produced by 

 bacilli carried on the legs and body or by regurgitation of the germ- 

 laden food or possibly by excrement. 



The paper concludes with a summary of the life-history and seasonal 

 prevalence of some of the species of flies which cause external myiasis 

 in the United States. The method of wintering of C . 7na cellar i a has not 

 been definitely determined. Experiments in keeping adult and 

 immature stages through the winter proved unsuccessful. Certain 

 facts indicate that the species normally dies out in the winter, except 

 possibly in the extreme southern parts and in the tropics, and re- 

 infestation of the country progresses as the season advances. The 

 first infestations of live-stock are found in May ; September and 

 October are usually the months of greatest injury. A partial checking 

 of the ravages of the species may occur in the hot and dry midsummer. 

 In western Texas, years with abnormally heavy rainfall are generally 

 most productive of infestation. The period from emergence of adults 

 to deposition of eggs ranges from 3 to 18 days. Under the most 

 favourable conditions, the depositions may occur at intervals of two 



