Comstock, J. H. 1940. (Revised and edited by W. J. Gcrtsch.) The Spider 

 Book. Doubleday, Doran and Co. New York. 



Emerton, J. H. 1902. Common Spiders. Ginn and Co. Boston. 



EwincT, H. E. 1933. Afield with the Spiders. Nat. Geog. Mag., Vol. 64, 

 No. 2. 



Gertsch, W. J. 1949. Amcriean Spiders. D. Van Nostrand Co. New York 



McCook, H. C. 1889-1893. American Spiders. 3 vols. Philadelphia. 



Passmore, L. 1933. California Trapdoor Spider Performs Engineering Mar' 

 vels. Nat. Geog. Mag., Vol. 64, No. 2. 



Petrunkevitch, A. 1939. Catalogue of American Spiders. Trans. Conn. 

 Acad, of Arts and Sciences, Vol. 33. New Haven, Conn. 



Savory, T. H. 1928. The Biology of Spiders. Macmillan. New York. 



Worley, L. G. and Pickwell, G. B. 1931. The Spiders of Nebraska. Univ. 

 Studies, Vol. 27. Lincoln, Neb. 



The family names used as first choice in the spider key are those given in 

 Petrunkevitch's Catalogue. 



MYRIAPODA 



The Myriapoda are known to most people as centipedes and millipedes or 

 hundred-legs and thousand-legs, but their small economic importance and the 

 difficulty of identification have left them generally disregarded. All of them 

 are terrestrial, air-breathing animals. Representatives of the group are to be 

 found in almost all parts of the world. A few, such as the house centipede, 

 Scutigera, occasionally cause the housewife much consternation by unexpected 

 appearances in bathtubs and sinks. Others are common in gardens, some feed' 

 ing on plant roots and some preying on earthworms and insects. These are 

 commonly called wireworms, a popular name which is frequently applied to 

 the larval forms of several kinds of beetles. Many of the group are so small 

 as to escape notice, and even the largest forms in the United States are seldom 

 longer than six inches. 



The classification is not fully agreed upon and the term Myriapoda is rc' 

 tained for the group largely as a matter of convenience rather than as imply- 

 ing any close relationship between the four subdivisions it contains. Even the 

 common names of millipede and centipede are unsatisfactory, as many of the 

 centipedes actually have more legs than do the millipedes. 



Related to the Diplopoda or millipedes are two groups of small, soft-bodied 

 forms, the Symphyla and the Pauropoda. The latter two are not good material 

 for fossilization, but the Diplopoda are to be found as fossils in Carboniferous 

 rocks and a few in Devonian sandstone. They seem to be most nearly related 

 to the annelid worms and to be the most ancient of the Myriapoda. The Diplo' 

 poda usually have two pairs of legs on each of most of the body segments and 



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