Larvae Of The Nearctic Species Of The Stonefly Genus Megarcys Klapálek (Plecoptera: Perlodidae) Author Stewart, Kenneth W. Department of Biological Sciences, P. O. Box 305220, University of North Texas, Denton, Texas, U. S. A. 76203 E-mail: stewart @ unt. edu stewart@unt.edu Author Kondratieff, Boris C. Department of Bioagricultural Sciences and Pest Management, Colorado State University, Fort Collins, Colorado, U. S. A. 80523 E-mail: Boris. Kondratieff @ Colostate. edu Boris.Kondratieff@Colostate.edu text Illiesia 2012 8 3 16 36 journal article http://doi.org/10.5281/zenodo.4760667 dd6866c0-c326-4347-8419-b2e688a89062 1854-0392 4760667 Megarcys yosemite ( Needham & Claassen 1925 ) ( Figs. 1 , 54-59 , 69 , 74 , 78, 83 , 88 a-b, Table 1 ) Distribution. California , Washington (high elevation streams). Material examined. California : Inyo Co. , Ruby Creek , about 56.33km from the Mt. Lyell Type Locality, El. 3444m , water temp. 12.2°C, 20-VIII- 2010 , L. Serpa , 1 pre-emergent larva (died in rearing), 4 early instar larvae (on a previous date in 2008, 1♂ determined by R . Baumann , and 1♀ larva, were collected by L. Serpa at this site; personal correspondence); Mono Co. , Coldwater Creek , 37°34 27.4 ’’ N 118° 59 16.7 ’’ W , El. 3063m , water temp. 4.44°C, 19-VIII-2010 , L. Serpa, 2 reared brachypterous ( one ♂ determined by R .W. Baumann ), 2 brachypterous larvae, 4 brachypterous larvae, 6 early instar larvae with average head capsule width of 1.14mm , and average body length of 5.64mm ; Coldwater Creek , Sky Meadow , 2.7km above Coldwater Creek Campground , El. 3067m , water temp. 4.49°C, 2 reared , 1 reared ( Fig. 1 ), 6 larvae (5 died in rearing: 07-IX-2010 collection date, 17-IX- 2010 emergence date) (personal correspondence, J. Sandberg ). Characters. Head capsule width 2.88-3.36mm , 3.60-3.84mm ; pronotal width 2.76-3.30mm , 3.54-3.66mm ; body length 17.64-20.2mm , 22.4- 22.9mm ( Table 1 ). Color and pigmentation ( Figs. 54- 59 ), lacinia, and dorsomesal band of erect silky white hairs typical of genus. Wingpads of ( Figs. 55 , 78 ) and brachypterous, reflective of adults. Gill number and arrangement typical of genus ( Fig. 69 ). Submental gill length 0.27-0.36mm , 0.33- 0.45mm; anterior supracoxal gill length 0.18- 0.30mm, 0.24-0.33mm ( Table 1 ). Legs ( Fig. 56 ) with setation typical of genus. Y-arms of mesosternum ( Fig. 57 ) typical of genus. Cercal segments 24-26 ( Table 1 ), with setation typical of genus. Developing membranous windsock-like process of male epiproct ( Figs. 59 , 74 ) evident in late instar individuals, and pointed posteroventrally in lateral view ( Fig. 83 ). Developing female subgenital plate of 8 th sternum ( Fig. 88a, b ) shallowly notched mesally. Comments. Males and females ( Fig. 1 ) of this high elevation California population are brachypterous, reflected by the very short wingpads of preemergent larvae. The submental and anterior supracoxal gill lengths of both sexes of larvae, like the brachypterous male larvae of M. subtruncata larvae of Quinn Spring, Oregon , and brachypterous male and macropterous female larvae of M. watertoni from Iceberg Creek, Montana , were substantially shorter than those of the macropterous populations studied ( Table 1 ). Otherwise, coloration and pigmentation, generic, and other specific characters of larvae were not separable from the other four species.