THE FLIES THAT CAUSE MYIASIS IX MAX 159 



lacks pubescence but bears three rows of setulae; Immoral, presutural. and 

 sternopleural bristles are absent. Larva (fig. 9-">) : The larva is slender, cylindri- 

 cal, and translucent, tapering anteriorly into a cone and truncated posteriorly, 

 with three pairs of protuberances on the last segment, the ventral pair being very 



prominent. The mature larva measures 6-8 mm. in length and becomes some- 

 what whiter and more opaque than the preceding stages. 



Geographical Distribution. — Almost cosmopolitan. Nearctic Region: Green- 

 land. Alaska. Canada (to the Arctic Zone). Labrador. Quebec. Alberta. Maine, 

 Xew Hampshire. Vermont. Massachusetts. Rhode Island, Connecticut. Xew Y<»rk. 

 Xew Jersey. Pennsylvania. Maryland, District of Columbia, North Carolina, 

 Georgia. Florida. Alabama. Mississippi. Ohio, Michigan. Minnesota. Wisconsin, 

 Missouri. South Dakota, Kansas. Louisiana. Texas. Montana, Idaho, Colorado. 

 Xew Mexico, "Washington, Oregon. California. Neotropical Region : Mexico. Costa 

 Rica. Bermuda. Jamaica. Colombia. Ecuador. Brazil. Bolivia. Chile. Argentina. 

 Patagonia. Palaearctic Region: Scotland, England, France, Netherlands, Italy. 

 Sardinia. Sicily, Sweden. Germany. Austria. Greece, European Russia (northward 

 t" Arkhangelsk), Canary Islands. Madeira. Libia. Egypt, Siberia. Oriental 

 Region: India, Sumatra. Java. Ethiopian Region: Belgian Congo, Uganda. 

 Australian Region : Queensland, Xew South Wales. Xew Zealand. Marquesas 

 Islands, Hawaiian Islands. 



Biology and Pathogenesis. — Both adults and larvae seek the dark. 

 Eggs may be laid on meat such as smoked or cured ham. on ohee>e. 



Figure 95. — Piophila casei, mature larva 



and on other food substances. Eggs sometimes hatch in 1 day in warm 

 weather. Development is rapid, and the life cycle may be completed 

 in as few as 11 to 12 days, although it usually requires from '1 weel^ to 

 a month. There are three larval instars; the third-stage larvae de- 

 velop a habit of leaping, especially when disturbed, which gives the fly 

 its common name. By virtue of their .-lender shape and pointed an- 

 terior end, they can crawl into very small cracks and into the connective 

 tissue between muscle bundles of preserved meat: for this reason they 

 are often found unusually deep in preserved foodstuffs. 



A summary of the pathogenic role of this species in human myiasis 

 is given by Simmons {1^.1). Experimental evidence has shown that 

 the larvae can pass through the intestine of dogs alive, and that in >o 

 doing they produce serious intestinal lesions. Evidently the same is 

 true of man. Numerous eases of intestinal myiasis have been reported ; 

 it has even been known to pupate and emerge as an adult, thereby 

 producing interne colic in its host. This is considered the most com- 

 mon of insects found in the human intestine. One case of nasal my- 

 iasis, accompanied by a profuse nasal discharge and pain of several 

 weeks' duration, and another in which larvae were "expectorated by a 

 patient suffering from an infection of the chest.'' have been reported 

 (Austen -5). Both these reports were substantiated when the larvae 

 were reared to the adult stage. 



Literature. — Simmons (HI) gives an extended account of the biol- 

 ogy, immature stages, and medical importance of this species. 



The Family SEPSIDAE 



These are small, slender, shining black or reddish flies, which look 

 somewhat like ants. The head is spherical; the anterior pari of the 

 front lacks bristles ; the vibrissae are pre>ent. though often weak ; palpi 



