174 PROCEEDINGS OF THE NATIONAL MUSEUM VOL. 106 



Zapus h. hudsonius 



Warren County: June 17, 1948, 

 DU-1, CEF-3; June 18, 1948, 

 USNM-Type+5, DU-1. 

 Microtus p. pennsylvanicus 



Clearfield County: Apr. 16, 1949, 

 CEF-1; Apr. 24, 1949, CEF-3. 



Synaptomys cooperi stonei 



Clearfield County: Apr. 22, 1949, 

 CEF-1. 

 Napeozapus i. insignis 



Clearfield County: May 4, 1949, 

 DU-4, RML-2, CM-2; May 5, 

 1949, DU-5, KU-1, Afr-1, Aus-1. 



Seasonal distribution: E. diversa acuta has been collected 

 only during the spring months, April, May, and June. 



Geographic distribution: E. diversa acuta has been col- 

 collected in two counties, Clearfield and Warren, in northwestern 

 Pennsylvania (fig. 4,6). 



Diagnosis: E. diversa acuta can be distinguished from other 

 members of the E. rubra group by the form of its palpal claw, 

 the reduced number of setules on the lateral seta of the palpal 

 tibia, the relatively high number of setules on the galeal seta, 

 and by its geographic range. 



Ecology: According to Mr. Neil Richmond, the hosts in War- 

 ren County, Pa., v/ere collected in a hay meadow and in the sur- 

 rounding thickets of blackberry, elm, hawthorn, and pin cherry. 

 The area was located on a flat, well-drained floodplain of the 

 Allegheny River. The summer season was well advanced. Over 

 100 Microtus and 70 to 80 Peromyscus, as well as Blarina, Con- 

 dylura, and Tamiasciuriis, were trapped v/ith few or no chiggers. 



The chiggers were attached deep in the pinna on Zapus and 

 to the scalp below and behind the pinna. 



Cultures: Two cultures of E. diversa acuta nymphs were 

 established. One culture was in a pint jar with the bottom re- 

 moved and the opening plugged with plaster-charcoal. In the 

 second a base of plaster-charcoal was poured into the intact jar. 

 Forest soil was used as a medium in both. Aedes aegypti eggs 

 were offered as food in both. No further development of the 

 nymphs occurred. 



Life history : From collection dates and culture records it was 

 determined that engorged larvae of E. diversa acuta metamor- 

 phosed into nymphs in 12 days or less. One living nymph was 

 observed in a culture 29 days after the culture had been estab- 

 lished. 



Remarks : E. diversa acuta has been named from the form of 

 its palpal claw. 



The forms comprising the "rubra" group are obviously related. 

 They are bound together by their morphology, their seasonal dis- 

 tribution, and their geographic range. However, variations occur 

 within the pattern of the group, and the morphological difl^erences 

 are correlated with geographic distribution so that the separate 



