44 



MISC. PUBLICATION 318, U. S. 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 insect 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. All these factors are helping, but more immediate or drastic 

 control measures are necessary, and chemicals poisonous to insects 

 must be used in many cases. 



Figure 105. — Chewing mouth parts (left) ; sucking mouth 

 parts (right). 



Ill 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 

 winch 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). 



Figuee 106. — Lacewing. 



