An Elementary Study of Insects | Page 4

heart, the blood vessels being absent. In this way
the internal organs of the insect are simply bathed in the blood. The
system of respiration is most complicated. The air is taken in through
pores usually along the side of the body and is then carried through fine
tracheal tubes to all parts of the body. You cannot drown an insect by
putting its head under water, since it does not breathe through its mouth.
The muscular system is similar to that of other animals which have the
skeleton on the outside.
[Illustration: The internal organs of the honey bee. Note the strong
wing muscles in the thorax. The tube-like heart begins in the head and
extends back through the thorax and follows the curve of the abdomen.
Below the heart is the digestive tube consisting of the slender
oesophagus which extends back to the expanded honey stomach, in
which the bee carries the nectar it collects from flowers, then the curled
true stomach, the small intestine and expanded large intestine. Below
this is the nervous system consisting of the brain and a chain of
connected enlargements or ganglia extending back into the abdomen in
the lower part of the body. The respiratory system in part appears just
above the honey stomach, and the black circular or oval spots are cross
sections of connecting air tubes, which run all through the body. Also
note the sting with the poison gland and sack which are pulled out with
the sting; also the sucking tube for getting honey from flowers, and the
structures on the legs for gathering and carrying pollen; the pollen
basket is on the back side of the hind leg.]
Their Methods of Developing
In most cases the parent insect deposits small eggs which hatch later
into the young insects. In some cases, as with the blow-flies, the
maggot may hatch from the egg while yet in the parent's body, when
the active larva is born alive. Whether the egg hatches before or after it
is deposited, the young insect continues to develop in one of three ways.

It may resemble the parent and simply grow as does a kitten, or it may
look somewhat like its parent though smaller and without wings, as the
young grasshopper, or it may bear no resemblance whatever to the
parent, as the caterpillar which feeds and grows and finally spins a
cocoon in which it passes to the resting chrysalis stage and later
emerges with wings. The development of insects is therefore extremely
complicated.
[Illustration: The chinch bug showing development with incomplete
metamorphosis; a, egg; b, first nymph; c, second nymph; d, third
nymph; e, fourth nymph; f, adult winged bug; g, chinch bugs extracting
sap from corn plant. To control this pest burn over all winter harboring
places and use chemical or dust barriers following wheat harvest.]
The Principal Orders
In order to study a group of animals which includes so many thousand
different kinds it is necessary to divide them into a number of sharply
defined divisions or orders. All animal life is naturally grouped into
such divisions and subdivisions. Among the insects we at once detect
seven large, sharply defined divisions or orders, and ten or more
smaller ones. Of these we have first, the two-winged true flies; second,
the four-winged butterflies and moths; third, the hard-backed beetles;
fourth, the stinging four-winged wasps and bees; fifth, the variously
formed sucking insects or true bugs, as chinch bugs and bed-bugs; sixth,
the rapid-flying four-winged snake doctors or dragon-flies and, seventh,
the hopping forms, the grasshoppers. Besides these we have the various
smaller orders of water-loving insects, fleas, etc. The seven groups
mentioned above include the majority of our common forms and in the
studies to follow we will include only representatives from these
orders.
[Illustration: The Hessian fly showing development with complete
metamorphosis; a, egg; b, larva or maggot; c, flax-seed stage; d, pupa; e,
adult winged fly; f, wheat stubble with flax-seed stages near base taken
after harvest. To control this pest, plow under stubble after harvest;
keep down all volunteer wheat and sow wheat after fly-free date in the
fall.]

Their Habits
The habits of insects are as varied as their forms and adaptations. Some
live in the water all their life, others spend a part of their life under
water, others live the care-free life of the open air, others enjoy feeding
upon and living in the foulest of filth, others associate themselves with
certain definite crops or animals thereby doing untold injury, while
others produce food and other materials which are to be used by man
for his comfort. Every imaginable nook and crook, from the depths of
lakes to the tops of mountains, from the warm, sunny south to the cold
frigid north, from the foul damp