PROCEEDINGS OF THE UNITED STATES NATIONAL MUSEUM 



SMITHSONIAN INSTITUTION 



U. S. NATIONAL MUSEUM 



Vol. 84 Washington: 1937 No. 3006 



CRESTED MILLIPEDS OF THE FAMILY LYSIOPETALI- 

 DAE IN NORTH AMERICA, WITH DESCRIPTIONS OF 

 NEW GENERA AND SPECIES 



By H. F. LooMis 



Bureau of Plant Industry, United States Department of Agriculture 



With an Inteoductoby Account of Distribution and Specialized Chabactees 

 IN Collaboration with O. F. Cook, Bubh:au of Plant Industry 



Studies of hrnnus faunas in different regions of the United States 

 afford many data of geographic distribution in the several groups 

 of arthropods that live in the soil. Most of the millipeds are defi- 

 nitely restricted to the humus conditions, and they afford some of 

 the most striking contrasts in geographic distribution. The crea- 

 tures that do not survive drying necessarily are confined to places 

 where moisture is held through the dry season, and such limitations 

 greatly restrict the distribution of species. The humus conditions 

 prevail more widely and continuously in the rainfall regions of the 

 Southeastern States, and in that region the species of millipeds have 

 a relatively wide distribution, while in the arid climate of the 

 Southwestern States localized species are the rule. 



Very little of the southwestern country has continuous moisture 

 in the soil, and favorable conditions for humus faunas usually are 

 restricted to the higher altitudes. Wide stretches of open deserts 

 intervene where no surface humus is found and only a few kinds 

 of millipeds are able to exist by retreating to the burrows of the 

 desert mammals. For most of the millipeds the deserts are im- 

 passable barriers that separate completely the more elevated dis- 

 tricts where the animals can live. From the standpoint of the milli- 



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