222 PROCEEDINGS OF THE NATIONAL MUSEUM VOL. 106 



occur on marmots, have been collected only in spring and summer. 

 E. blarinae, E. carolinensis, E. crateris, E. ohioensis, and E. pipi- 

 strelli appear to be active at all seasons. There is obvious diag- 

 nostic value in a seasonal distribution such as that of E. rubra in 

 which the species is restricted to certain months of the year. 

 However, further collections, particularly of the sort that are 

 made around the year in relatively restricted localities, should be 

 available before determinations of the systematic value of 

 seasonal distributions are attempted. 



The systematic significance of the ecology of North American 

 Euschongastia can be discussed only in an introductory manner. 

 Ecological information for the eastern species is fragmentary. 

 Nothing is known of the western species beyond the information 

 on the slide labels. Almost nothing has been done with the free- 

 living stages, including the chigger itself before attachment. 

 However, it was on the basis of ecology that Ewing (1929d) sepa- 

 rated the vertebrate-infesting trombiculids from the arthropod- 

 infesting trombidiids. Indications of differences in ecology are 

 contained in the results of collections at a standing dead oak stub 

 (pi. 2) and in the region of an andropogon field (pi. 3) in Duke 

 Forest. It is to be anticipated that acarologists will use the data 

 of ecology to diagnose at the level of species as the information 

 is acquired. 



Although this paper is concerned only with the parasitic chig- 

 gers, it is important in any discussion of the ecology of these mites 

 to remember that the other stages of the trombiculid life cycle 

 are not parasitic. Disregarding the physical factors of the en- 

 vironment, the trombiculid life cycle demands food in the form of 

 suitable arthropod eggs or tissues during the nymphal and adult 

 stages. Hosts are necessary for the larvae, or chiggers, during 

 the parasitic stage. Since the larvae obviously cannot move far 

 from the locality in which the adults reproduce, it follows that 

 this locality must lie within the range of suitable hosts. 



The ecological niches of the free-living stages of Euschongastia 

 remain almost unexplored. The preliminary investigations in the 

 Duke Forest area were generally inconclusive so far as characters 

 of systematic importance are concerned. There is some evidence 

 that free-living E. peromysci are associated with well-decayed 

 stumps. There is negative evidence that the niches of the other 

 species were not found. Wharton's (1946) discovery of the free- 

 living stages of E. indica in the nests of its host suggests a pos- 

 sibility for North American species, but nests occupied by the 

 common hosts were not found during the present study. Further, 



