46 



Insects and Disease 



parasite is to be found in several different kinds of 

 native animals which seem to be practically im- 

 mune but are always a source of danger when other 

 animals are introduced. Two or three species of 

 tsetse-flies are responsible for the transmission of 

 this disease. 



Another group of flies much smaller but more 

 numerous and much more insistent are the black- 

 flies or buffalo-gnats (Fig. 24). For more than a 

 century these little flies have been recognized as 

 among the most serious pests of stock, particularly 

 in the south where, besides the actual loss by death 

 of many animals yearly, the annoyance is so great 

 as to sometimes make it impossible to work in the 

 field. Human beings are often attacked, and as 

 the bite is poisonous and very painful great suffer- 

 ing may result and cases of deaths from such 

 bites have been reported. 



Belonging to another family, and smaller, but 

 much like the buffalo-gnat in habits, are the minute 

 little "punkies" or "no-see-ums" which sometimes 

 occur in great swarms in certain regions where 

 they make life a burden to man and beast. While 

 it has not been shown that either the buffalo-gnats 

 or the punkies are responsible for the transmission 

 of any disease, their habits of feeding on so many 

 different kinds of wild and domestic animals as 



