CHIGGERS — ^FARRELL 



141 



Eyes : Two pairs lateral to the posterolaterals ; no ocular plate. 

 Diameter of anterior eyes, 10 to 12, mean 10.3; of posteriors, 

 8 to 10, mean 8.3. 



Dorsal setae: Posterior group different in form from the an- 

 terior setae ; anteriors well clothed with setules on the side oppo- 

 site the body ; posterior group with fewer, shorter setules exposing 

 the shaft. Measurements from three specimens: Length of 

 humerals, 61 to 72; of setae near the middle of the first post- 

 humeral row, 50 to 57 ; of setae in the posterior group, 37 to 47. 



Dorsal formulae of three specimens from Ravalli County, 

 Mont. : 



2 . . 12 . . 11 . . 2 . . 11 . . 7 . . 2 . . 2 (paratype) 

 2 . . 13 . . 14 . . . . 12 . . 11 . . 8 . . 2 

 2 .. 11 .. 15 .. .. 12 .. 8.. 5 .. 4 



Ventral setae : Generally similar to dorsals. Data from three 

 specimens: Number of first sternals, 2; of second sternals, 2; 

 of poststernals, 52 to 60. Length of first sternals, 50 to 57; of 

 second sternals, 40 to 44; of setae near the middle of the first 

 poststernal row, 30 to 44 ; of setae in the posterior group, 33 to 47. 



Anomaly: One specimen with three second sternals. 



Material: Paratype in the U. S. National Museum; other 

 specimens from the Rocky Mountain Laboratory now deposited 

 in the Duke University collection. Specimens from hosts, all from 

 Montana : 



Pika 

 Ravalli County: Dec. 2, 1933, 1 

 (paratype). 



Ochotona p. princeps 



Ravalli County: Dec. 2, 1933, 1. 

 Clethrionomys sp. 



Ravalli County: Oct. 12, 1945, 1. 



Seasonal distribution : E. samboni has been collected in fall 

 and winter, October and December. 



Geographic distribution : E. samboni has been collected only 

 in Ravalli County, Mont. (fig. 4,a) . 



Diagnosis : E. samboni can be distinguished by the following 

 combination of characters: Tibiala III, subterminala and para- 

 subterminala I, and genualae I present; five prongs, usually, on 

 the palpal claw ; two pairs of eyes ; galeal seta usually branched ; 

 lateral seta on palpal tibia nude. E. samboni is very close to E. 

 oregonensis, as the species are now defined. In the specimens 

 studied, all the setae of the gnathosoma of E. samboni are larger; 

 the galeal seta is heavier and the setules longer; and the lateral 

 seta on the palpal tibia is nude. 



