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THE POPULAR SCIENCE MONTHLY 



of that generic term may be. Some of these diseases have been care- 

 fully worked out, but how many more remain of which we know nothing 

 as yet, I would not even dare to guess. 



The effect of the tsetse fly or its bite on horses in South Africa 

 has been long known, but just how that effect is produced is a matter 

 of more recent knowledge. We know now that the disease is produced 

 by Trypanosomes carried by the flies, and this information has opened 

 the way to intelligent treatment. 



Here again, be it noted, the order Diptera contributes the bulk of 

 the dangerous species to the mammalian types, and to our horses, 



Fig. 9. A silver-fish, Lepisma sp. ; from Howard, U. S. Department of Agriculture. 



cattle and sheep, the elimination of all flies would be as great a boon 

 as to man himself. 



Heretofore I have spoken only of insects that either attack or in- 

 fluence the health of man or other animals. But there are numerous 

 others that live with him and are messmates, sharing in the produce 

 that he has stored for his own use, and in this work members of almost 

 every insect order are concerned. 



The Thysanura are represented by various species of Lepisma or 



