MYIASIS— TYPES OF INJURY, LIFE HISTORY, HABITS 177 



tearing a^vny of tissues, as exliibitcd by species in this group. This is 

 the most dangerous tj'pe of m3'iasis in man and one of the most important 

 sources of loss due to insects among domestic animals. As previously 

 pointed out, practically all the flies included in this group attack living 

 animals as a secondary method of reproduction. 



It should be stated most emphatically that cases of myiasis, either in 

 man or animals due to species in this group, are more or less intimately 

 associated with violations of the best sanitary principles. The vast 

 majority of cases of this type of myiasis occur in the warmer parts 



Plate IX.— Carcass partly destroyed by larvae of the American screw-worm fly, 

 Chrysomya macellaria. (Bishopp.) 



of the world. In the United States, as is well known, our principal source 

 of trouble is due to the Muscoid fly, Chrysomya macellaria Linnaeus, 

 commonly spoken of as tlie screw-worm (see plate I, fig. 3; plate II; plate 

 IX). Several other species are concerned to a greater or less degree, 

 among these should be mentioned the black blow fly, Phormia regma 

 Meigen (plate I, fig. 4), the green bottle flies, Lucilia casar Linnaeus 

 (plate I, fig. 2) and L. sericata ]\Ieigen, certain of the flesh flies (Sarcoph- 

 aga spp. (plate III, fig. 1) and occasionally some of the hairy blow- 

 flies of the genei'a Cynomyia and Calliphora. 



Fortunately from the standpoint of the sanitary entomologist, the 

 methods of control are in general very much the same for all species of 

 this group, owing to the similar habits and not vastly different life his- 



