for the citations to the genera) , a discussion which includes the biology, 

 the economic or medical importance with emphasis on the species 

 involved, and a series of references to pertinent literature. In addition 

 line drawings of the representatives of the families are included. 



The Acarina are still poorly known even by specialists in the group. 

 Therefore, it is anticipated that many changes will have to be made 

 before a definitive work on the group is achieved. In many cases very 

 little is known about certain famiHes. When it is realized that the 

 Acarina represent an area for investigation in systematics, ecology, 

 and economic zoology that is practically virgin territory, we can see 

 that we are truly on the threshold of a new and exciting field. 



The authors wish to thank Drs. R. E. Beer, G. M. Kohls, H. H. J. 

 Nesbitt, A. E. Pritchard, and R. W. Strandtmann for their helpful 

 advice and crhicism. 



Edward W. Baker and G. W. Wharton 



