TRAPDOOR SPIDERS. 



363 



holes in the ground, and sometimes conceals the opening by 

 covering it with a few dead leaves. Our largest spider is 

 NepMla 2:>lnmipes of the Southern States. The common 

 garden spider is Epeira vulgaris Hentz. It lives about 



Fig. 320. — Development of the Spider. — .4, worm-like stage ; i?, primitive band ; 

 C, ttie same more advanced, with rudiments of limbs, 



houses and in gardens ; its geometrical web is very regular. 

 The large trap-door spider (Mygale) has four lung-sacs in- 

 stead of two, as in the other spiders, and only two pairs of 

 spinnerets. Mygale Henzii Girard 

 inhabits the Western plains and 

 Utah ; Mygale avicularia Linn, of 

 South America is known to seize 

 small birds, and suck their blood. 

 There are probably about six or 

 eight hundred species of spiders 

 in North America ; their colors 

 are often brilliant, and sometimes, 

 from the harmony in their colora- 

 tion with that of the flowers in 

 which they hide, or the leaves on 

 which they may rest, eliide the 

 grasp of insectivorous birds. 



Sub-olass 4. Hexapoda. — The 

 triregional division of the body 

 genuine winged insects than in the Myriopods and spiders. 

 They have compound as well as simple eyes ; two pairs of 



Fig. 321,— Embryo Spider, still 

 more advanced. This and Fi;^. 320 

 after Claparede, 



is better marked in the 



