FIG. 177. =Illustrated Study of Dragon Fly.=—3 shows dragon fly laying its eggs in water while poised on wing. Describe the larval form (water tiger). The extensible tongs are the maxillæ enlarged. The pupa (1) is active and lives in water. Where does transformation to adult take place (5)? Why are eyes of adult large? its legs small? Compare front and hind wings. Do the eyes touch each other? Why is a long abdomen useful in flight? Why would long feelers be useless? What is the time of greatest danger in the development of the dragon fly? What other appropriate name has this insect? Why should we never kill a dragon fly? ] [Illustration: FIG. 178.—The tarantula. ] [Illustration: FIG. 179.—Trap-door spider. ] [Illustration: FIG. 180. ] [Illustration: FIG. 181.—Anatomy of spider. ] [Illustration: FIG. 182.—Laying egg. ] [Illustration: FIG. 183.—Foot of spider. ] =Illustrated Study of Spiders= (Figs. 178–183).—The tarantula, like most spiders, has eight simple eyes (none compound). Find them (Fig. 178). How do spiders and insects differ in body? Number of legs? Which have more joints to legs? Does trap-door spider hold the door closed (Fig. 179)? How many pairs of spinnerets for spinning web has a spider (_Spw_, 180)? Foot of spider has how many claws? How many combs on claws for holding web? Spiders spin a cocoon for holding eggs. From what part of abdomen are eggs laid (_E_, 182; 2, 181)? Find spider’s air sacs, _lu_, Fig. 181; spinning organs, _sp_; fang, _kf_; poison gland, _g_; palpi, _kt_; eyes, _au_; nerve ganglia, _og_, _ug_; sucking tube, _sr_; stomach, _d_; intestine, _ma_; liver, _le_; heart, _h_, (black); vent, _a_. Give two reasons why a spider is not an insect. How does it place its feet at each step (Fig. 110)? Does the size of its nerve ganglia indicate great or little intelligence? Why do you think first part of body corresponds to both head and thorax of insects? The following Farmer’s Bulletins, (revised to 1921) are available for distribution to those interested, by the United States Department of Agriculture, Washington, D.C.—