[Illustration: FIG. 175.--Bed bug. × 5.] [Illustration: FIG. 176.--Life history of mosquito.] =Illustrated Study of Insect Pests= (Figs. 171-176).--Why does the _clothes moth_ (171) lay its eggs upon woolen clothing? How does the larva conceal itself? The larva can cut through paper and cotton, yet sealing clothes in bags of paper or cotton protects them. Explain. The _house fly_ eats liquid sweets. It lays its eggs in horse dung. Describe its larval and pupal forms. Banishing horses from city would have what beneficial effect? Describe the _louse_ and its eggs, which are shown attached to a hair, natural size and enlarged. Describe the _bed bug_. Benzine poured in cracks kills bed bugs. Do bed bugs bite or suck? Why are they wingless? Describe the larva, _f_, pupa, _g_, and the adult _flea_, all shown enlarged. Its mandibles, _b_, _b_, are used for piercing. To kill fleas lather dog or cat completely and let lather remain on five minutes before washing. Eggs are laid and first stages passed in the ground. How does the _mosquito_ lay its eggs in the water without drowning (176)? Why are the eggs always laid in still water? Which part of the larva (wiggletail) is held to the surface in breathing? What part of the pupa (called tumbler, or bull head) is held to the surface in breathing? Give differences in larva and pupa. Where does pupa change to perfect insect? Describe mouth parts of male mosquito (at left) and female (at right). Only female mosquitoes suck blood. Males suck juice of plants. Malarial mosquito alights with hind end of body raised at an angle. For figure see Human Biology, Chap. X. Why does killing fish and frogs increase mosquitoes? 1 oz. of kerosene for 15 ft. of surface of water, renewed monthly, prevents mosquitoes. What is the use to the squash bug (Fig. 184) of having so bad an odor? [Illustration: FIG. 177.] 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.]