94 



Illustrated Studies 



Fig. 183. — Foot of spider. 



Illustrated Study of Spiders (Figs. 178-183). —The tarantula, like most spi- 

 ders, 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 (S/>w, 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 (£, 182; 

 2, 181) ? Find spider's air sacs, hi. Fig. 181 ; spinning organs, s/> ; fang, kf \ poison 

 gland, g; palpi, kt\ eyes, an ; nerve ganglia, og, ug\ sucking tube, sr ; stomach, d\ 

 intestine, ma\ liver, le ; heart, k, (black) ; vent, a. Give two reasons why a spider 

 is not an insect. How does it place its feet at each step (Fig. no) ? (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 ? 



