PHYLUM ARTHROPODA — CLASS ARACHNIDA 295 



begin to eat one another. Many spiders live only one year, develop- 

 ing from over-wintering eggs in the spring, growing to maturity dur- 

 ing the summer, laying eggs, and then dying in the fall. Some spiders 

 live two or three years, while other species live many years. 



Classification of the Arachnida 



For purposes of this chapter we shall confine our discussion to but 

 five of the common orders of the class Arachnida : (1) Araneida, the 

 true spiders; (2) Acarina, the mites and ticks; (3) Scorpionida, the 

 scorpions; (4) Phalangida, the daddy longlegs; and (5) Xiphosura, 

 the king crabs. 



According to a recent study, A Natural Classification of Spiders, by 

 Dr. A. Petrunkevitch, the order Araneida is made up of sixty-two 

 families. Species of many of these families are rarely encountered, 

 and some of them are not found in America. The following eight 

 families, however, are common in the United states : 1. Lycosidae, the 

 wolf spiders. This family contains many of the largest native species. 

 They are found mainly upon the ground running around in search 

 of food. The females carry the cocoons attached to their abdomens. 

 The eyes are arranged in three rows of four, two, and two. The 

 species, Lycosa gulosa, L. kochii, L. frondicola, and Allocosa parva 

 are common species in the western states. 



2. Theridiidae, the comb-footed spiders. The spiders of this fam- 

 ily are found on low growing vegetation, fences, buildings, and at 

 times under boards and rocks. They build rather loose webs from 

 which they hang back downward. Members of this family have a 

 toothed comb on the tarsi of the fourth pair of legs, three claws, 

 and eight eyes. The black widow, Latrodectus mactans, reported as a 

 poisonous species, is a member of this family. The hourglass on the 

 ventral part of the abdomen is scarlet in color in the live spider. 



3. Thomisidae, crab spiders. These crablike spiders do not con- 

 struct webs, but lie in wait in the flowers for insects that visit them. 

 They are often highly colored for protection. They possess eight 

 eyes in two rows; the two anterior pairs of legs are longer than the 

 other legs ; and the body is rather flat. 3Iisumena vatia and Xysticus 

 nervosus are common species. 



4. Drassidae. The drassids live mainly on the ground, under stones, 

 or in silk tubes on shrubs and grass. The spinnerets are generally 

 long enough to extend a little behind the abdomen. The eyes are eight 



