SCREW-WORMS AND OTHER MAGGOTS 

 AFFECTING ANIMALS/ 



CONTKNTS. 



Page. 



Distribution and abundance of the screw- 

 worm 3 



Character of injury and losses duo to the 

 screw-worm 4 



Description of the screw-worm fly and its 

 olTspring .") 



Page. 



Life history and habits 7 



Control 9 



Other flies infesting wounds, including the 

 sheep wool-maggots 13 



THE so-called screw-worm - is a pest of prime importance to the 

 stock raisers of the Southwest. This insect gains its common 

 name from the habit of the larvse or maggots of penetrating prac- 

 tically sound tissue. Stockmen usually distinguish between the 

 screw-worm and Avhat they term maggots largely by the character 

 of the wound infested and the time of year. The screw-Avorm is 

 often confused with the other species, which commonly are spoken 

 of as maggots, especiall}^ during the spring and fall months. Injury 

 to live stock from maggots is more widespread than is that due 

 to the true screw-worm. In fact, this maggot injury may be found 

 among live stock in any State of the Union, although it occurs 

 most frequentl}^ in the warmer portions of the country. The true 

 screAV-worm inflicts enormous losses on the stock raisers of Texas, 

 Oklahoma, New Mexico, Arizona, and southern California during 

 seasons which are favorable for its development. During the warmer 

 portions of the year it is never entirely absent from this region and 

 may also cause injury to stock in the other southern States, and as 

 far north as Nebraska. 



The screw-worm is a native of the Americas and has been causing 

 trouble to stockmen for many years. No doubt it is largely due to 

 this fact that the cattlemen accept the pest as a necessary evil and 

 always count upon " doctoring " a certain number of cases every year. 



DISTRIBUTION AND ABUNDANCE OF THE SCREW-WORM. 



The screw-worm fly occurs from the extreme southern part of 

 South America northward into Canada, but it seldom becomes 



1 Throughout the investigations upon which this bulletin is based Mr. E. W. Lanke has 

 been associated with the authors. He was concerned especially with work on the life 

 histories of the various animal-infesting flies, details of which will be published later. 

 The photographs, except that of figure 5. were made by Mr. H. P. Wood. 



- Known scientifically as Chrysomyla macellaria Fabricius. 



3 



