44 MISC. PUBLICATION 318, U. 8. DEPT. OF AGRICULTURE 
Through commerce, man has upset Nature’s balance, and many 
insects have been accidentally introduced and their natural enemies 
have been left behind. Many plants have been introduced which 
provide better food for native insects than native plants provide, thus 
stimulating the rapid reproduction of these favored insects. Certain 
plant breeding has made plants more susceptible to imsect attack. 
Then, also, one phase of our agricultural system—the planting of 
large acreages of one kind of crop in a concentrated area—has made 
it possible for insect pests to Increase in such destructive numbers 
that they can cause serious damage. 
In recent years quarantines have been put into effect which regu- 
late the shipment of plants and animals. Plant breeders are work- 
ing toward greater resistance in plants to insects and diseases. Much 
work with parasites is being done to help Nature reestablish her 
balance. A1l these factors are helping, but more immediate or drastic 
control measures are necessary, and chemicals poisonous to insects 
must be used in many cases. 
FicuRBn 105— Chewing mouth parts (left); sucking mouth 
parts (right). 
Tn the earlier days, a blanket recommendation was made—stomach 
poisons for chewing insects and contact sprays for sucking insects. 
Now an effort is being made to use less and less of the metallic 
poisons. The organic or plant-product sprays have been found to be 
much more specific, and the old rule does not always apply. A person 
must know much more about insects and insecticides (spray material) 
than was formerly necessary if he hopes to control insects adequately. 
This control phase of the project is for the purpose of acquainting 
the club member with insect habits and the effect of different control 
measures. 
COLLECTION AND IDENTIFICATION 
In addition to studying insect control and life habits, club members 
of second-year groups should endeavor to collect and prepare notes 
on eight orders of insects not included in the first-year work. Some 
of the orders listed below contain many small insects, specimens of 
which should be mounted on small cardboard points or preserved in 
alcohol or formaldehyde. 
NEUROPTERA.—Neuron (nerve), pteron 
(a wing). Four large leaflike wings, nearly 
equal in size, usually finely netted; wings 
notched, held rooflike over back when at 
rest. Antennae long. Mouth parts for chew- 
ing. Life changes (metamorphosis) com- 
plete. Larvae of some living in the water. 
Dobson flies, aphis lions, ant lions (doodle- 
bugs). 
FIGURE 106.—Lacewing. 
ee ee ended 
ee ee oe 
nantes  _ 
