=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? [Illustration: FIG. 184.--Squash bug, or stink bug.] The following Farmer’s Bulletins are available for free distribution to those interested, by the U. S. Department of Agriculture, Washington, D.C.:-- Farmer’s Bulletin No. 47, Insects affecting the Cotton Plant; No. 59, Bee Keeping; No. 70, The Principal Insect Enemies of the Grape; No. 80, The Peach Twig Borer; No. 99, Three Insect Enemies of Shade Trees; No. 120, The Principal Insects affecting the Tobacco Plant; No. 127, Important Insecticides; No. 132, The Principal Insect Enemies of Growing Wheat; No. 145, Carbon Bisulphid as an Insecticide; No. 146, Insecticides and Fungicides; No. 152, revised, Mange in Cattle; No. 153, Orchard Enemies in the Pacific Northwest; No. 155, How Insects affect Health in Rural Districts; No. 159, Scab in Sheep; No. 165, Silkworm Culture; No. 171, The Control of the Codling Moth; No. 172, Scale Insects and Mites on Citrus Trees; No. 196, Usefulness of the Toad; No. 209, Controlling the Boll Weevil in Cotton Seed and at Ginneries; No. 211, The Use of Paris Green in controlling the Cotton Boll Weevil; No. 212, The Cotton Bollworm; No. 216, The Control of the Boll Weevil; No. 223, Miscellaneous Cotton Insects in Texas; No. 247, The Control of the Codling Moth and Apple Scab. [Illustration: FIG. 185.--Female plant louse, with and without wings (enlarged).]