THE FLIES THAT CAUSE MYIASIS IN MAX 



39 



destruction of that organ. The maggots never penetrate the digestive 

 organs and are not known to cause myiasis of the digestive tract : how- 

 ever, they may penetrate deeply into thick muscles and damage them 

 severely. 



Status as a Parasite. — From all indications this is a specific myiasis 

 producer. Records by early authors indicating that this species is a 

 scavenger are, according to Portchinsky, probably due to misidentifi- 

 cation. 



Literature. — An extensive treatment of this fly and of its history. 

 biology, pathogenic aspects, and life history, illustrated, is given by 

 Portchinsky ( 118) . and various cases of myiasis involving W. mag- 

 nified are discussed by Salem ( 127) . 



WOHLFAHRTIA VIGIL (Walker) 



(Fig. 11) 



Synonym.— Para phyto chittendeni Coquillett 



Recognition Characters. — Adult : This species differs from all other known 

 members of the genus in that the usual black abdominal spots are large and 

 confluent, the abdomen consequently appearing black with gray pollinose spots. 

 Larva: This is similar to that of W. magnified, with a similar distribution of 

 spinous areas; the spines, however, are not so coarse. The anterior spiracle has 

 nine or ten papillae, and the peritreme of the posterior spiracles is thinner (fig. 9). 



Geographical Distribution. — Nearctic Region : Alaska, Nova Scotia, New 

 Brunswick, Quebec. Ontario, Manitoba, Alberta, British Columbia, Maine, New 

 Hampshire, Massachusetts. New York, Pennsylvania, Ohio, Michigan. Minnesota, 

 Wisconsin, Iowa, North Dakota, South Dakota, and Idaho. Most cases of myiasis 

 have been reported from Minnesota, the adjoining Dakotas, and southern Ontario. 



Biology and Pathogenesis. — Development is rapid, the life cycle 

 being completed in 30 to 36 days under conditions in southeastern 

 Canada. Larviposition takes 

 place from 11 to IT days after 

 the emergence of the adult. 

 the larvae mature in 7 to 9 

 days, and the pupal period 

 lasts 10 to 12 days. 



The human cases recorded 

 are babies under 5 months of 

 age who have slept out of 

 doors unprotected by nets or 

 screens. The exception re- 

 corded by Felt (39,p.l7o) of 

 the case of a maggot, sup- 

 posed to be this species, taken 

 from a small cyst in the con- 

 junctiva of a man was a mis- 

 identification. 



Larvae are deposited in 

 groups on exposed parts of 

 the body ; after larviposition, 

 they separate and wander 

 about, sometimes for consid- 

 erable distances, before penetrating the skin. Unlike W. magnified^ 

 the larvae enter the unbroken skin, but are capable of doing so only 

 if the skin is tender. The female My, in her larviposition response. 



Figure 11. — Wohlfahrtia vigil, adult female. 



