PART Ilii—TELLING OTHERS ABOUT INSECTS 
[Introduction to third-year work] 
Members of the group organized for third-year insect study will, in 
addition to continuing with insect collecting, be ready to carry to 
other club members and to adults their knowledge gained from pre- 
vious study. The third-year outline of work should include giving 
plays and demonstrations, preparing and displaying exhibits, and 
making surveys. Through these devices, entomologists and exten- 
- sion workers may be aided in getting correct insect-control informa- 
tion into the hands of many persons who otherwise would not be 
reached. The great number of insects and the wide variety of con- 
trol practices provide almost limitless work for club members to do 
in this field. 
| COLLECTION AND IDENTIFICATION 
There is a difference of opinion as to the total number of orders of 
insects, but it is about 25. Representatives of some orders are very 
rare and would seldom be picked up for collections. However, seven 
orders, in addition to those already described, are listed here, and 
specimens of some of them can be located with sufficient effort. 
DERMAPTERA.—Derma (skin), pteron (a wing). Front 
wings beetlelike (leathery), but much shorter than abdo- 
men. Hind wings earshaped, veins radiating from middle 
forward margin. Often wingless. Cerci (forceplike struc- 
tures) on tip of abdomen. Mouth parts for chewing. Life 
changes (metamorphosis) incomplete. Earwigs. 
FIGURE 127.—Earwig. 
CORRODENTIA.—Corrodens (gnawing). Minute in- 
sects, wingless or with four membranous wings with few 
prominent veins; wings, when present, folded rooflike 
over body. Mouth parts for chewing. Life changes very 
slight. Booklice, dust lice, bark lice, deathwatches. 
FIGURE 128.—Booklouse. 
TRICHOPTERA.—Thrix, genitive trichos (a _ hair), 
\ pteron (a wing). Four similar membranous wings; hind 
—= pair shorter and broader. Mouth parts modified for chew- 
ing. Antennae long, legs long. Life changes complete. 
Frauen 129,—Caddisfy, Larvae living in water. Caddisflies. E 
