232 PROCEEDINGS OF THE NATIONAL MUSEUM vol. loi 



Also possessing most of these characteristics in common are type 

 specimens of the following North American species: HaemogamasiiS 

 reidi Ewing, 1925 ; H. twitchelli Ewing, 1925 ; Euhaemogamasus ony- 

 chotnydis Ewing, 1933 ; E. oregonensis Ewing, 1933, and E. sciuropteri 

 Keegan, 1946. These differ from one another almost entirely in num- 

 bers of setae on dorsal, genitoventral, and anal shields and in numbers 

 of dorsal and ventral body setae. When these species were described 

 it was assumed that, as in species of several other subfamilies of 

 Laelaptidae, numbers of genitoventral and anal setae were specifically 

 constant and were useful taxonomic aids. Accordingly, Ewing de- 

 scribed H. twitchelli as possessing eight anal setae and H. reidi as 

 possessing only three. One of the diagnostic features of genus Euhae- 

 mogamdsus Ewing, 1933, was possession of three anal setae. E. ore- 

 gonensis was further characterized as having about 20 genitoventral 

 setae. E. sciuropteri was to be separated from other species of the 

 genus by possession of five anal setae and 28-30 genitoventral setae. 



First indication of variation in numbers of both genitoventral and 

 anal setae was discovered upon examination of the type specimens of 

 each species. Five of the seven female specimens on the type slide of 

 H. reidi possessed 24, 30, 18, 22, and 25 genitoventral setae ; six of the 

 seven specimens had 3, 3, 4, 4, 5, and 6 anal setae. The type female of 

 H. twitchelli had about 50 genitoventral setae and eight anal setae. 

 The type female of E. onychomydis had about 50 genitoventral setae 

 and at least six anal setae. Each of two females on the type slide of 

 E. oregonensis had about 45 genitoventral setae and eight and seven 

 anal setae. Hirst (1914) reported that numbers of anal setae of 

 European specimens of ambulans varied from seven to nine. 



Specimens in the U. S. National Museum collection previously iden- 

 tified as H. tioitcheUi, H. reidi, E. onychomydis, and E. oregonensis 

 include the types of each species and a total of 150 specimens taken 

 from a variety of hosts and habitats from several of the eastern, cen- 

 tral, and western United States and southern Canada. The type fe- 

 male of E. sciuropteri was deposited in the collection of the Army 

 Medical Museum. Upon examination of this series it was found that, 

 like the types, all possessed the most distinctive characteristics of E. 

 ambulans, differing from it, and among themselves, in the following 

 characteristics: Numbers of setae on dorsal, genitoventral, and anal 

 shields and on dorsal and ventral body surfaces; length-width ratio 

 of sternal shield; relative size of genitoventral shield; slight differ- 

 ences in structure of posterior end of peritreme ; presence of basal seta 

 on fixed chela. These characteristics were found to vary to the fol- 

 lowing extent: 



Setation or dorsal shield and dorsal and ventral body surfaces : 

 It is difficult to express the relative thickness or sparseness of setation 



