PHYLUM ARTHROPODA — CLASS ARACHNIDA 



297 



in holes, and under debris in the daytime. They feed upon beetles 

 and other ground-living insects. Eurypelma steindachneri and E. 

 hentzi are common tarantulas. 



8. Pholcidae, the pholcids, are spiders with long legs and six or 

 eight eyes. They build loose webs in dark places, such as cellars and 

 protected corners of buildings. There are six genera in the United 

 States. Pholcus phalangioides is a large species. The abdomen is 

 elongated in form, and the legs are one and one-half to two inches 

 long. In this species the chelicerae are used to carry the eggs. Three 

 species are found in the genus Physocyclus : two of them are Physo- 

 cyclus glahosus which is found in Florida and P. tanneri, in Utah. 



Fig-. 168. 



Fig. 169. 



Fig. 170. 



Fig. 168. — The brown mite, Bryobia praetiosa. (Greatly enlarged.) (After 

 Sorenson, by permission of the Utah Agricultural Experiment Station.) 



Fig. 169. — An adult female, red spider, Tetranychus telarius. (After Knowlton, 

 by permission of the Utah Agricultural Experiment Station.) 



Fig. 170. — An adult blister mite, Eriophyes pyri. (After Sorenson, by permission 

 of the Utah Agricultural Experiment Station.) 



For a discussion of the other spider families found in this country, 

 the student should consult the most valuable treatise on this subject, 

 The Spider Book, by Professor John H. Comstock. 



Order Acarina. — Mites and ticks are mostly small creatures with 

 the cephalothorax and abdomen fused solidly together. They are, in 

 the main, ectoparasites or endoparasites ; however, some of the aquatic 

 species are able to shift for themselves, living upon various small 

 water animals. All mites lay eggs Avhich hatch into six-legged 

 n;^^nphs. After some growth and moulting they develop into adults 

 with eight legs. 



