THE FLIES THAT CAUSE MYIASIS IN MAN 151 



KEY TO SPECIES 



ADULTS 



1. Eye on the middle third with a definite band of pile which is distinctly 



denser than that of the anterior or posterior third; third abdominal 

 segment wholly shining; arista with pubescence which is not longer 



than its diameter; honeybeelike species tenax (Linnaeus) 



Eye without a zone of denser pile in the median third; third abdominal 

 segment with opaque, black areas; arista with some hairs which are 

 longer than its diameter ; beelike, but not honeybeelike, species 2 



2. Face with a polished area on and around the tubercle and usually with 



a brownish or blackish vitta ; aristal pubescence but little longer 

 than its diameter ; third abdominal segment with a small round opaque 



spot in addition to the preapical band dimidiata (Wiedemann) 



Face entirely pollinose, aristal pubescence several times its diameter; 

 third abdominal segment with a prebasal as well as a preapical opaque 

 band arbustorum (Linnaeus) 



TUBIFERA TENAX (Linnaeus) 



The Drone Fly 

 (Fig. 91) 



Synonyms. — Eristalis tenax (Linnaeus), Eristalomyid tenax (Linnaeus). 



Recognition Characters. — Adult : This species is similar to the drone honeybee 

 in its general appearance. The antennae are brownish black; the arista is not 

 plumose, but has distinct short pubescence on its basal part. The pilosity of 

 the eyes is arranged in the form of three vertical bands, the middle one being 

 much denser than the anterior and posterior ones. The thorax is uniformly dark 

 but clothed with some yellowish hair ; the abdomen is shining, black and reddish 

 yellow, the amount of the reddish yellow varying and sometimes predominating. 

 Length about 15 mm. Larva : Some characters of the larva are discussed by 

 Johannsen {62, pp. 27-28), but it would be unsafe to indicate any as diagnostic. 



Geographical Distribution. — The general distribution seems to be almost 

 world-wide, yet lacking or rare in many tropical areas. Nearctic Region : New 

 Brunswick, Quebec, Ontario, Alberta, British Columbia, Maine, New Hampshire, 

 Vermont, Massachusetts, Rhode Island, Connecticut, New York, New Jersey, Penn- 

 sylvania, Maryland, District of Columbia, Virginia, North Carolina, Georgia, Ohio, 

 Michigan, Indiana, Illinois, Minnesota, Wisconsin, Missouri, Nebraska, Kansas, 

 Louisiana, Montana, Idaho, Colorado, Utah, New Mexico, Washington, Oregon, 

 California. Neotropical Region : Mexico, Bermuda, Peru, Uruguay, Chile, Argen- 

 tina, Patagonia. Palaearctic Region: Ireland, Scotland, England, Spain, Gi- 

 braltar, France, Netherlands, Italy, Corsica, Sardinia, Sicily, Malta, Norway, 

 Sweden, Lapland (Swedish), Denmark, Germany, Czechoslovakia, Austria. 

 Hungary, Rumania, Greece, European Russia, Azores, Cape Verde Islands, 

 Canary Islands, Madeira, Morocco, Algeria, Tunisia, Libia, Syria, Iran, Siberia, 

 Lake Baikal Region, China, Manchuria, Chosen, Japan. Oriental Region: India. 

 Ceylon, Burma, Federated Malay States, Taiwan. Ethiopian Region: South 

 Africa (Transvaal, Cape of Good Hope), Madagascar, Reunion Islands. Austral- 

 ian Region: New South Wales, Victoria, New Zealand, Hawaiian Islands. 



Biology and Pathogenesis. — The larvae live in water contaminated 

 by sewage, liquid excrement, decaying carcasses, and other foul organic 

 matter; occasionally they ma}' be found in relatively clean water. 

 They may also breed in manure of a soft or liquid consistency, or in 

 decaying plant and animal matter. 



The larva is extremely resistant to adverse conditions. Numerous 

 authors, including Linnaeus, have noted the ability of the larvae to 

 withstand crushing pressure. Austen (J) cites an instance in which 

 they went through dyeing vats alive, and another in which the}' lived 

 in rock pools containing rotting seaweed, where the}' were exposed to 

 changing salinity and to the hot sun each day. 



A number of cases of gastrointestinal myiasis caused by this species 

 have been reported. Some may have been due to subsequent contami- 



