]^48 PROCEEDINGS OF THE NATIONAL MUSEUM VOL. 10« 



Pitymys sp. 

 Pennsylvania 



Cameron County: Sept. 1949, 3. 

 Monroe County: Sept. 1949, 1. 

 Bradford County: Nov. 1949, 14. 

 Leaf nest in log 

 North Carolina 



Orange County: Oct. 1949, 7. 

 Durham County: Mar. 1950, 2. 



Microtus ch7-otorrhinu8 

 Pennsylvania 



Sullivan County: Oct. 1949, 4. 

 Ondatra zibethica 

 North Carolina 

 Durham County: Nov. 1949, 2. 

 Soil (7 to 15 cm. depth?) 

 North Carolina 



Orange County: Jan. 1950, 2. 



Seasonal distribution : In North Carolina E. peromysci has 

 been collected from hosts in every month of the year except Oc- 

 tober (fig. 6,c). There is a record of unattached chiggers for 

 October. The species is much more abundant on hosts during the 

 winter and spring months. 



Geographical distribution : The range of E. peromysci, based 

 on known collections, extends from Oklahom.a in the southwest 

 and North Carolina in the south to Massachusetts in the north- 

 east (fig. 4,a). 



Diagnosis : E. peromysci can be distinguished by the following 

 combination of characters: Tibiala III present, subterminala 

 and parasubterminala I present, palpal claw with three prongs, 

 no mastitarsala III, sensillae capitate, and scutum with two ridges, 

 one anterior to each pseudostigma. Through the range known 

 at the present time, the shape of the scutum and the characteristic 

 galeal setae v/ill separate E. peromysci from other known 

 Euschongastia species. 



Ecology: Mr. Neil Richmond has supplied information con- 

 cerning areas in which E. pe^-omysci was collected in Pennsyl- 

 vania. The chiggers commonly were taken from hosts trapped 

 in situations where hemlock was a dominant tree. Associated trees 

 in the various areas included yellow and black birch, red maple, 

 and oaks. The sites frequently were ravines or slopes with north- 

 ern or partially northern exposures. Moisture was ample to 

 abundant; springs and brooks were usually present. The forest 

 floor held a moderate to deep layer of humus. Logs and fallen 

 branches were abundant. Most collections were made from 

 Clethrionorays gajyperi. 



In the Duke Forest area E. peromysci was taken from its hosts 

 trapped in upland hardwoods (pi. 1) in all exposures and in the 

 narrow bottomlands along streams. Generally the topography 

 of this area is gently rolling, cut by four permanent streams. 

 The forest floor holds a moderate amount of humus, fallen 

 branches, decaying logs, and fallen trees. Stumps in varying 

 stages of decay are common, as are cavities and passageways left 

 by decayed stumps and root systems (pi. 2) . 



