m malaria is about twelve thousand,
entailing an annual monetary loss of about $100,000,000, to say nothing
of the suffering and misery endured by the afflicted. All this on
account of two or three species of insects belonging to the mosquito
genus _Anopheles_.

Yellow fever, while not so widespread, is more fatal and therefore more
terrorizing. Its presence and spread are due entirely to a single
species of mosquito. Flies, fleas, bedbugs, and many other insects have
been shown to be intimately connected with the spread of several other
most dreaded diseases, so it is no wonder that physicians, entomologists
and biologists are studying with utmost zeal many of these forms that
bear such a close relation not only to our welfare and comfort but to
our lives as well.

It would be out of place to try to give here even a brief outline of the
classification of insects, such as may be found in almost any of the
many books devoted to their study.

The most generally accepted classification divides the insects into
nineteen orders; as the Coleoptera, containing the beetles; the
Lepidoptera, containing the butterflies and moths; the Hymenoptera
containing the bees, ants and wasps, etc. Four or five of these orders
will be of more or less interest to us.

The order Diptera, or two-winged flies, is the most important because to
this belong the mosquitoes which transmit malaria and yellow fever, and
the house-fly that has come into prominence since it has been found to
be such an important factor in the distribution of typhoid and other
diseases.

FLIES

The order Diptera is divided into sixty or more families, many of which
contain species of considerable economic importance. For our present
consideration the flies may be divided into two groups or sections:
those with their mouth-parts fitted for piercing such as the mosquito
and horse-fly, and those with sucking mouth-parts such as the house-fly,
blow-fly and others.

Some of the species belonging to the first group are among the most
troublesome pests not only of man but of our domestic animals as well.
Next to the mosquitoes the horse-flies (Fig. 22) are perhaps the best
known of these. There are several species known under various names,
such as gad-fly, breeze-fly, etc. They are very serious pests of horses
and cattle, sometimes also attacking man. Their strong, sharp, piercing
stylets enable them to pierce through the toughest skin of animals and
through the thi