Missouri State Record for Polypedilum (Pentapedilum) Tritum Walker (Diptera: Chironomidae) Based on Larval Identifications from Wadeable Streams

INTRODUCTION Polypedilum (Pentapedilum) tritum (Walker) has a widespread Holarctic dis tribution (Stone et al., 1965; Oliver et al., 1990; Caldwell et al., 1997; Oyewo and Saether, 2008). However, Epler (2001) noted the name P. tritum may represent more than one species in the southeastern USA. We identified larvae of P. tritum in samples collected from 27 of 224 wadeable streams sampled in Missouri during the years 2008-2010. Streams where specimens of P. tritum were collected were sampled during 28 March and 16 to 18 September, 2008, 31 March and 1 April, 2009, and 23 March to 6 April, 2010 in the Osage Plains, Ozark Highlands, and Central Dissected Till Plains ecological sections of Missouri (Cleland et al., 1997; Nigh and Schroeder 2002) (Fig. 1). Our records of P. tritum represent the first for this species in Missouri, although larvae of this species may have been misidentified as members of the Polypedilum illinoense group in earlier collections. The undeveloped posterior lobe in the ventromental plates, antennae with vestigial Lauterborn organs and long segments 3 and 4, and the sunken first lateral teeth of the mentum should be a unique set of characters to distinguish larvae of P. tritum from larvae of other described species (for full description see Oyewo and Saether, 2008). However, there are 52 recognized species in the subgenus Pentapedilum, but only 11 of those have larval descriptions (Oyewo and Saether, 2008). Although undescribed larvae of some Polypedilum species may, possibly, have characteristics in common with some diagnostic characteristics of larval P. tritum, we are confident in our identifications of lar val P. tritum based upon the description for larvae of this species provided by Oyewo and Saether (2008). Volume 122, Number 2, March and April 2011 165