THE PHYLOGENY OF THE GALL MITES AND A NEW 



CLASSIFICATION OF THE SUBORDER PROSTIGMATA 



OF THE ORDER ACARINA. 



By H. E. EwiNG, 

 Bureau of Entomology, U. S. Department of Agriculture. 



Of all the major groups of the Acarnia it is doubtful if any 

 are more aberrant than the gall mites, and but few show such 

 unity of organization or sameness of habits. Because of this 

 there has been in the past but little evidence upon which to 

 establish any natural affinities between them and any of the 

 other groups, while suggestions as to their origin have been 

 but little more than conjectures. 



RECENT VIEWS IN REGARD TO THE AFFINITIES OF THE 

 GALL MITES. 



By way of both introduction and review, here are given 

 some of the more recent views in regard to the relationships 

 of the gall mites. 



In 1910 Dahl commited himself to the belief that the gall 

 mites were related to the other Acarina through the Tar- 

 sonemidae. He regarded the genus Tarsonemus as representing 

 a transitional stage between the Eriophyidae and the Acarina 

 proper. This belief was held largely because of the nature of 

 the last pair of legs. These legs, normally developed in the 

 free-living Tarsonemidae, are shortened and almost rudi- 

 mentary in some of the parasitic species. He found in this 

 group the tendency toward leg reduction which has been so 

 completely effected in the Eriophyidae. 



Banks (1915) champions the Tarsonemid theory. In his 

 well known treatise on the mites he states: "The Eriophyidae 

 are, perhaps, more closely related to the Tarsonemidae than to 

 any other group. Many of the Tarsonemidae feed exposed on 

 the leaves or stems of a plant; some of them cause swellings 

 or deformities of the plant, and some have the body more or less 

 distinctly segmented. Moreover, in several genera of the 

 TarsonemidcC there is a tendency toward reduction in the 

 number of legs, and in other genera the hind legs are very 



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