220 PROCEEDINGS OF THE NATIONAL MUSEUM VOL. 106 



photographs with which he very effectively supplemented his 

 descriptions and his drawings. These photographs make possible 

 a visualization which cannot be achieved through written descrip- 

 tions or drawings. Also, by use of such photographs, the acarolo- 

 gist can approach, as closely as is possible, his desire to observe 

 and compare specimens side by side, after the manner of the 

 mammalogist. In the present work photography has been used 

 as a systematic aid in a manner similar to that used by Brennan, 

 although the phase microscope was substituted for the technique 

 of oblique light. 



Geography follows morphology in importance in the practical 

 study of systematics. Wallace (1880) said, "Each species is 

 moreover usually limited to one continuous area. . . ." Thus, the 

 geographic range may be used as a check on the morphological 

 species. There is no literature on the geographic distribution of 

 North American Euschongastia beyond the locality records ac- 

 companying the original descriptions of species. Collections re- 

 main meager. Through wide areas (fig. 8,6) records are com- 

 pletely lacking. The ranges, therefore, are incompletely known, 

 but in every case where the range of a species has been charted a 

 logical geographic area has been indicated (figs. 4, 7, 8). When- 

 ever the range is at all extensive, such as that of E. pipistrelli, 

 E. peromysci, or E, setosa, a few intermediate collections point 

 toward continuity of range. 



Further, chiggers of the genus Euschongastia have been col- 

 lected extensively in the West in a few counties of Montana and 

 Idaho. In the East extensive collections have been made over 

 much of Pennsylvania and a few counties of Ohio and North 

 Carolina. The species collected in each region have been distinc- 

 tive. Due regard must be given to the blank spaces on the map 

 (fig. 8,6), but no eastern species has been reported from the 

 West. No western species has been collected in the East. How- 

 ever, at this time the evidence by no means permits any real 

 delimiting of ranges for any species. E pipistrelli, E. peromysci, 

 and E. diversa diversa have the greatest extent of range from 

 east to west known at present. But the westward limits may 

 reflect merely the lack of collectors. Purely as an aid to study, 

 species which for the present may be regarded as eastern include 

 E. pipistrelli, E. peromysci, E. rubra, E. magna, E. diversa 

 diversa, E. diversa acuta, E. marmotae, E. hamiltoni, E. hlarinae, 

 E. carolinensis, E. crateris, E. ohioensis, and E. setosa. Species 

 which may be regarded as western include E. lacerta, E. bige- 

 nuala, E. oregonensis, E. samboni, E. cordiremus, E. guntheri, 



