62 THE BOOK OF THE FLY 



Internal protozoal parasites and parasitic worms 

 breed in and are disseminated by the house-fly ; so also 

 are the fungic spores of fermentive yeasts, of moulds, 

 and the like, but these latter are mainly disseminated 

 by mere air currents. The eggs of tape-worms and 

 the like are carried by dung-frequenting flies to food, 

 especially to semi-putrid food devoured by dogs and 



Pigs- 

 Some of the skin-piercing and blood-sucking flies 

 are pestiferous in a more direct way than any of the 

 tribes of filth and sweat-flies. They are the usual or 

 suspected agents whereby anthrax, cattle-plague, swine 

 fever, glanders, and other diseases are spread far and 

 wide. Some of these last blood-sucking flies will 

 travel with and on the bodies of transported animals 

 for long distances ; of course there can be no doubt 

 also as to the capability of disease dissemination by 

 the direct independent flight of flies to long distances 

 with favouring weather and breeze. Such evils are 

 prevalent throughout the temperate zones, but cir- 

 cumstances are far worse in the tropics, where Glossina 

 morsitans, considered by some to be a near relation of 

 our Stomoxys calcitrans, transmits the microscopic 

 trypansomes which cause the devastating " sleeping 

 sickness" of mid-Africa. This last reference, and 

 other discoveries of the fly-borne germs of recurrent 

 fevers, should bring into prominent notice a very 

 pertinent fact, which has not yet received adequate 

 scientific investigation. All the bites of our common 

 blood-sucking insects, flies, gnats, midges, fleas, etc., 

 are each kind of them wounds, sometimes very in- 

 flammatory, sometimes but little or not at all so ; 



