CHIGGERS — FARRELL 143 



dency to fewer setules from south and west to north and east 

 (table 6). Chelicera with typical heavy base, curved blade, and 

 distinct subapical dorsal and ventral teeth. Cheliceral base and 

 palpal coxa and femur punctate. 



Legs: Striated setae in typical arrangement. Leg I with two 

 genualae and a microgenuala, two tibialae and a microtibiala, a 

 spur and a distal microspur, a subterminala, a parasubterminala, 

 and a pretarsala. Leg II with a genuala, two tibialae, a spur, 

 a proximal microspur, and a pretarsala. Leg III with a genuala 

 and a tibiala. All specialized setae strong and clear. Nonspecial- 

 ized setae on free segments beyond the trochanters rather short 

 but strong, with long, curved setules in regular alternate pattern. 

 All leg segments with punctae. 



Anomalies : One specimen with two setae on one coxa III. One 

 specimen with three genualae on one genu I. One specimen with 

 three tibialae I on one leg. One specimen with only one tibiala 

 II on one leg. One specimen with a parasubterminala I equal 

 in size to the subterminala. One specimen with the tibiala III 

 missing from one leg. 



Scutum: About a third to a fourth wider than long. x\nterior 

 margin broad W-shaped with the anterolateral setae and the 

 anteromedian seta on the anterior extensions. Lateral margins 

 concave, short, diverge slightly posteriorly. Posterolateral cor- 

 ners, very slightly extended, bear the posterolateral setae. Pos- 

 terior margin usually rather deeply rounded posterior to each 

 pseudostigma and shallowly concave between the two. Margins 

 sometimes so pared that scutum appears skimpy. Setae densely 

 covered with setules. Pseudostigmata well behind a line drawn 

 between the posterolateral setae. Sensillae abruptly expanded, 

 capitate; pedicels nude; heads covered with rather short setules. 

 Anterior to each pseudostigma an inverted U-shaped ridge, the 

 medial and lateral legs terminating about on a line with the 

 posterior edges of the pseudostigmata ; the two ridges sometimes 

 continuous medially. Surface punctate. Sometimes with cuticular 

 striae over the posterior margin. Apparently a tendency for 

 scuta to become larger from south and west to north and east in 

 the specimens from the area studied (fig. 5,a). 



Summary of standard data from 100 specimens of E. peromysci 

 from over its range (AL's from 99 specimens, AM's from 92, and 

 S's from 59) : 



AW 41-60, mean 50.2; PW 48-71, mean 66.6; AP 10-17, mean 13.5; 

 SB 17-32, mean 22.5; ASB 21-32, mean 27.3; PSB 6-12, mean 8.5; 

 AL 27-42, mean 34.9; AM 21-38, mean 26.8; PL 37-57, mean 46.4; 

 S 25-30, mean 27.1. 



