Bulletin 151, Truck and Garden Insects


Dozier, who made the photographs for the original illustrations.
The data on aphids were gathered chiefly by Mr. Mason, and
much of that relating to beetles by Mr. Dozier, who has also
worked out the life history of the okra caterpillar. The photo-
graphs for the major portion of the illustrations were supplied
by the Bureau of Entomology, U. S. Department of Agriculture.
Two were furnished by the North Carolina Agricultural Ex-
periment Station, one by the Porto Rico Experiment Station,
and one figure by the South Carolina Agricultural Experiment
Station.
 LIFE HISTORY OF INSECTS
 In order to apply remedial measures intelligently, it is
necessary to know something of the manner of development of
an insect; the different stages thru which it passes; the time
spent in each stage; its habits; etc. These make up its life
history."
 All insects during their lifetime, pass thru four more or
less well-marked and different stages: (1) The egg; (2) the
larva or active young; (3) the pupa or the transition stage; and
(4) the adult or perfect insect, technically called the imago, and
which usually possesses wings.
 In the life history of some insects, such as butterflies and
moths, beetles, and flies, the larva, called a caterpillar, grub, or
maggot, respectively, does not in the least resemble the adult
insect; and the pupa is inclosed in a rigid case incapable of
motion except for a twisting and turning of the abdomen, but
the pupa of the fly can often crawl. Such insects are said to
have a complete metamorphosis. In the life history of others,
as the true bugs and grasshoppers, the larva, commonly called
a nymph, resembles the adult insect, altho it is smaller, has no
wings and the organs of reproduction are but partly developed.
It may be active during the pupal stage and have little swellings
where the wings are to appear. Such insects are said to have
an incomplete metamorphosis.
 Hairless caterpillars are often called worms altho very
 different from true worms as represented by earth-worms
 (" fish-worms"), tape-worms, and nematodes.
 Some insects are most easily killed in the egg stage, others
 in the larval, pupal or adult stages. Close study of the life
 history of an insect will generally disclose its vulnerable points.
 Insects may be divided into two classes, biting and suck-
 ing, according to their method of taking food. The biting in-