THE FLIES THAT CAUSE MYIASIS IN MAX 25 



of characteristic form, which may. especially in the advanced instars, 

 be fused into one : these replace, in function, the mandibles of the more 

 primitive fly larva. In some cases an accessory oral sclerite (aos) is 

 present. The pharyngeal sclerite (phs) is a relatively large winglike 

 structure bearing an upper or dorsal horn i dh | and a lower or ventral 

 horn ( ch ). 



Deviation from the typical form, as above described, is common. 

 In the larva of Fanma, for example, the body is greatly flattened, the 

 individual segments are provided with a number of more or less pin- 

 nate processes, and the posterior spiracles are raised upon tubercles, 

 with the button, upon superficial examination, often appearing as a 

 fourth spiracular opening. In TeicJwmyza and Drosophila the pos- 

 terior spiracles are at the end of a pair of long stalks. In oestrid-. 

 hypodermatids, gasterophilids. and certain calliphorids. the larva is 

 grublike. 



In the lower families of Diptera. the larvae are quite different from 

 the muscoid type. Usually a distinct head which may be quite com- 

 plicated in structure (cf. Sylvicola fenestrates, fig. 87) is present. The 

 body form is extremely variable, but is usually not maggotlike. Usu- 

 ally, as in the muscoids. the larva is amphipneustic : that is, with a 

 pair of respiratory spiracles near each extremity: however, certain 

 larvae retain the more primitive peripneustic type, with schematically 

 a pair of spiracles to each segment. Sometimes, as in Tvibifera, ex- 

 tremely long posterior respiratory tubes are present. The body may 

 have numerous modifications ; these, together with the special terminol- 

 ogy applying to them, are discussed at the proper place in the system- 

 atic text. 



TECHNIQUE FOR REARING. PRESERVING, AND 



SHIPPING 



Many important records of myiasis-producing flies are lost because 

 of the improper handling of the material obtained. The following 

 paragraphs attempt to give only the minimum of entomological 

 technique and cannot by any means be considered a complete guide 

 for rearing, collecting, and preserving insects: it is hoped, however, 

 that they will serve the purpose of placing larvae and adults obtained 

 from cases of myiasis in the hands of competent specialists in a condi- 

 tion in which the material can be properly studied and determined. 



In the United States, the Bureau of Entomology and Plant Quaran- 

 tine. United States Department of Agriculture. Washington 25, I). C, 

 maintains an identification service; in some other countries a similar 

 service is available. 



REARING 



Since our knowledge of the taxonomy of immature forms of myiasis- 

 producing Diptera is so fragmentary, determinations of such material 

 often cannot be made with any degree of security. It is necessary, 

 therefore, whenever possible to rear some to the adult >tage. If there 

 is sufficient material of what might be assumed to be the same species, 

 some specimens should be preserved (^see directions) ; the others may 

 be reared. 



