n clothing of man. The bite is very severe and
irritating, and as the flies sometimes occur in great numbers the
annoyance that they cause is often very great indeed. It has often been
claimed that these flies as well as the stable-fly and others carry the
anthrax bacillus on their proboscis from one animal to another, and
although this may not have been definitely proven the evidence is strong
enough to make a very good case against the accused. It is interesting
to note in this connection that anthrax, a very common disease among the
domestic animals and one which may attack man also, was the first
disease to be shown to be of bacterial origin. It was only about
thirty-five years ago that the investigations of Koch and Pasteur
demonstrated that the presence of this particular germ (_Bacillus
anthracis_) was the cause of the disease, and it was early recognized
that such biting flies may be important factors in the spread of the
disease.

[Illustration: FIG. 22--Horse-fly (_Tabanus punctifer_).]

[Illustration: FIG. 23--Stable-fly (_Stomoxys calcitrans_).]

[Illustration: FIG. 24--A Black-fly (_Simulium sp._). (From Kellogg's
Amer. Insects.)]

[Illustration: FIG. 25--Screw-worm fly (_Chrysomyia macellaria_).]

[Illustration: FIG. 26--Blow-fly (_Calliphora vomitoria_).]

The stable-fly (Fig. 23) (_Stomoxys calcitrans_) which looks very much
like the house-fly and, as will be noted later, frequently enters
houses, is often an important pest of horses and cattle. Its
blood-sucking habit makes it quite possible that it too may be concerned
in carrying anthrax and other diseases.

In a later chapter it will be shown how the tsetse-fly, which is
somewhat like the stable-fly, is responsible for the spread of the
disease known as the sleeping sickness. This disease is caused by a
Protozoan parasite, a trypanosome, which is transmitted from one host to
another by the tsetse-fly.

In Southern Asia and in parts of Africa there is a very serious disease
of horses known as surra which is caused by a similar parasite
(_Trypanosoma evansi_). This parasite attacks horses, mules, camels,
elephants, buffaloes and dogs, and has been recently imported into the
Philippines. It is supposed that flies belonging to the same genus as
the horse-fly (_Tabanus_ and others), and the stable-fly (_Stomoxys_)
and the horn-fly (_Haematobia_) are responsible for the spread of the
disease.

Nagana is one of the most serious diseases of domest