A New, Dimorphic Species of Pyemotes and a Key to Previously-Described Forms (Acarina: Tarsonemoidea)

Two male and 2 female forms of a new, dimorphic species of Pyemotes from the scolytid Phleosinus canadensis Swaine are described and life history notes are presented. Only one type of female was found to be phoretic. Normal and phoretomorphic females can produce both normal and phoretomorphic daughters. Two species groups in Pyemotes, the scolyti group and the ventricosus group, are recognized and comparisons of morphological and behavioral adaptations for phoresy are made. Crossing experiments involving several forms indicate the probable existence of several closely related species in the ventricosus group, these often overlapping in their choice of hosts. A key to males of the genus and to females of the scolyti group is presented.