TRAP-DOOR SPIDERS. 343 
holes in the ground, and sometimes conceals the opening by 
covering it with a few dead leaves. Our largest spider is 
Nephila plumipes of the Southern States. The common 
garden spider is Hpeira vulgaris Hentz. It lives about 
B A Cc 
Fig. 315.—Development of the Spider.—A, worm-like stage; B, primitive band ; 
C, the 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 Henzti 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, elude the _ ; } 
- p : Fig. 816.—Embryo Spider, still 
grasp of insectivorous birds. more advanced. This and Fig. $15 
In their instincts and reasoning *%" lsparde- 
power, spiders are quite on a level with the insects, as 
proved by their nest- and web-constructing abilities. 
