CHAPTER XXVII 

 FLY MAGGOTS AND MYIASIS 



General Account. — Disgusting as it may seem, the human 

 body is attacked not only by the numerous adult flies discussed 

 in the last chapter, but is subject to attacks or invasion by the 

 maggots or larval stages of some species of flies. Such an in- 

 festation by fly maggots is commonly known as myiasis, intestinal 

 myiasis being the presence of fly larvae in the intestine, cutaneous 

 myiasis in the skin, etc. 



All of the maggots which habitually or occasionally parasitize 

 man belong to the order Diptera, and to the suborder Orthor- 

 rhapha, in which the larvae have very small and indistinct heads, 

 and the pupae are inactive oval bodies from which the adults emerge 

 by pushing off one end, like a cap (see p. 465 and Fig. 209A). 



Most cases of myiasis are caused by flies quite closely allied 

 to houseflies, and this famous transporter of germs and filth is 

 itself occasionally guilty. The identification of maggots is often 

 a difficult matter and is sometimes impossible without rearing 

 the adult insect. Larvae of the botfly family, CEstridae, are of 

 various shapes, but seldom taper evenly from the posterior to the 

 anterior end; the body has a leathery covering and is armed 

 with girdles of thornlike spines. Larvae of the genus Fannia 

 (Fig. 253) are flattened, and have very characteristic fleshy 

 processes along their sides. Nearly all other maggots causing 

 myiasis are cylindrical, whitish, footless creatures, tapering from 

 the broad posterior end to the small head, and are difficult to 

 identify. The chief characteristics used for distinguishing them 

 are the number and form of the mouth hooks (see Fig. 251), 

 and the nature of the respiratory openings at the posterior end 

 of the abdomen. These openings consist of two " stigmal plates," 

 hardened, yellowish, eyehke spots, in which are three slits or 

 openings, with sometimes a button-like mark at their base. 

 The relative position of the stigmal plates to each other and to the 

 surface of the larva, and the form of the slits, whether straight, 

 curved or wavy, and whether vertical or oblique, are some of 



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