opoda, which means "jointed-feet" and
includes the crayfish, crabs, spiders, mites, ticks and insects. Of
these only the last three are of interest to us now. It is customary to
speak of spiders, mites and ticks as insects, but as they have four
pairs of legs, instead of three pairs, in the adult stage, and as their
bodies are not divided into three distinct regions as in the insects,
they are placed in a different class.

GENERAL CHARACTERS OF TICKS

The ticks are all comparatively large, that is, they are all large
enough to be seen with the unaided eye even in their younger stages and
some grow to be half an inch long. When filled with blood the tough
leathery skin becomes much distended often making the creature look more
like a large seed than anything else (Fig. 14). This resemblance is
responsible for some of the popular names, such as "castor-bean tick,"
etc.

The legs of most species are comparatively short, and the head is small
so that they are often hardly noticeable when the body is distended. The
sucking beak which is thrust into the host when the tick is feeding is
furnished with many strong recurved teeth which hold on so firmly that
when one attempts to pull the tick away the head is often torn from the
body and left in the skin. Unless care is taken to remove this, serious
sores often result.

Ticks are wholly parasitic in their habits. Some of them live on their
host practically all their lives, dropping to the ground to deposit
their eggs when fully mature. Others leave their host twice to molt in
or on the ground. The female lays her eggs, 1,000 to 10,000 of them, on
the ground or just beneath the surface. The young "seed-ticks" that
hatch from these in a few days soon crawl up on some near-by blade of
grass or on a bush or shrub and wait quietly and patiently until some
animal comes along. If the animal comes close enough they leave the
grass or other support and cling to their new-found host and are soon
taking their first meal. Of course thousands of them are disappointed
and starve before their host appears, but as they are able to live for a
remarkably long time without taking food their patience is often
rewarded and the long fast ended.

Those species which drop to the ground to molt must again climb to some
favorable point and wait for another host on which they may feed for a
while. Then they drop to the ground for a second molt and if they are
successful in gaining a new host for t