22^ DISEASES DUE TO BACTERIA 



(4) By blood-sucking flies biting infected vertebrates sucking up 

 the pathogenic organisms and injecting them later into the body 

 of a healthy individual as the h^emamoeba^ of malaria, the 

 trypansome of sleeping sickness, the filarice of filariasis and the 

 unknown organism of yellow fever. 



(5) By biting flies causing local irritations and thus predisposing 

 tO' septic infection. 



(6) Bv^ the adult flies laying their eggs in wounds and the natural 

 orifices of the body like the green-bo'tle and the notorious screw- 

 worm fly, the larvae later burrowing their way into the tissues 

 and causing even mortal damage. 



(7) By the flies laying eggs on the food and the larv^ damaging the 

 victims' health resulting from their presence in the intestine. 



The ignorant and apathetic slum population suffer most, especially 

 in crowded bazaars and markets where offal is plentiful and sanitation 

 bad. 



HABITS, &c., OF THE MUSCA DOMESTICA (House-fly). 



Order. — Diptera (= with two wings). 



Suborder. — Cyclorrapha (= a circle; = suture). The imago escapes 

 from the puparium through a circular slit at the 

 anterior end. 



Section (2). — G. schizophora (= a cleft; = I wear). In these adults 

 the frontal suture is always well defined. 



Subsection (i). — Muscoidea. 



Family. — Muscid^e, including house-flies and tsetse-flies. 



Genus. — Musca domestica. Important in carrying typhoid fever; 

 •98 per cent, of flies infecting houses are Musca domestica. These 

 common flies are world-wide. Small, dull-coloured, blackish-grey 

 thorax, yellowish abdomen, with a median dark stripe. Arista 

 feathered dorsally and ventrally, proboscis soft, retractile and ends in 

 :a large fleshy labella. The fourth longitudinal vein bends forward at 

 an abrupt angle so as to nearly close the first posterior cell. In the 

 female the eyes are wide apart, in the male they are set close together. 



In hot countries they breed all the year round. 



In cooler countries they breed summer and autumn and then die 

 ■out except for a few sheltered ones. These survivors and new ones 

 which have hibernated, emerging from pup^e soon increase their kind 

 in warm weather. 



The female lays 120-150 eggs in a batch in any moist rubbish heap, 

 stable sweepings, vegetable debris, house refuse, &c. The white, 

 shiny, sticky eggs hatch in twenty-four hours in warm weather. 



The larva or maggot is whitish, cylindrical, tapers anteriorly, has 

 Iwelve segments and a very minute head. It has a pair of large, black 



