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218 of that generic term may be. Some of these diseases have been carefully 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,

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 influence 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