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 watertoni ( Ricker 1952 ) ( Figs. 17 , 23 , 29 , 35 , 41 , 47 , 53 , 65-68 , 73 , 75-77, 82 , 87 , Table 1 ) Distribution. Northern Rocky Mountains; Idaho , Montana , Alberta, British Columbia. Material examined. British Columbia: Kooteny National Park , 8-VII-1985 , 2♂ , 2♀ , many exuviae. Montana : Carbon Co. , Baring Falls , 28-VII-1989 , B. Stark et al., 1♀ larva; Rock Creek , 0.8 km below Glacier Lake Trailhead , 22-VII-1989 , B. Stark , 1 brachypterous ♂ (to Ab9), 1 brachypterous ♂ (to Ab 5), 4♀ , 1♀ larva; Glacier Co. , Baring Creek , Sunrift Gorge , Glacier National Park , 22-VII-1979 , K. Stewart , R . Baumann, B . Stark, 4♂ larvae, 5♀ larvae; Iceberg Creek at Iceberg Lake , Glacier National Park , 29-VII-1969 , R . Haick , 2 brachypterous ♂ , 1♀ ; 3-VII- 1972 , J. Stanford , 3♂ larvae, 1♀ larva; 21-VII-1979 , K. Stewart , R . Baumann, B . Stark, 1♂ larva, 1♀ larva; Roes Creek , Rising Sun Campground , Glacier National Park , 6-VII-1963 , coll.?, 3♂ , 3♀ ; Flathead Co. , Bear Creek / jct. Middle Fork Flathead River , Hwy. 2, 7-VI-1996 , R . Hansen, B . Ward ( C. Nelson # 6347), 1♂ larva, 1♀ larva; Juliet Creek , Bob Marshall Wilderness , 19-VII-1981 , J. Stanford , 1♀ ; Lion Creek , 14-VII-1985 , K. Stewart , 4♂ larvae, 4♀ larvae; Logan Creek at Logan Pass , Glacier National Park , 11-VII- 1987, K. Stewart , 1♂ larva; 2100 m , 10-X-1991 , J. Giersch , 5 small larvae; Logan Creek /confluence McDonald Creek , Glacier National Park , 29-VI-1995 , J. Giersch , 2♂ , 1♀ ; Spotted Bear River at Pentagon , Bob Marshall Wilderness , 21-VII-1981 , J. Stanford , 1♂ larva. Figs. 54-59. Megarcys yosemite larval male characters, Cold Water Creek, California. 54. Head-pronotum. 55. Wingpads. 56. Left middle and hind legs. 57. Meso-metasterna. 58. Dorsal abdomen. 59. Developing genitalia, dorsal. Characters. Bear Creek, Montana , macropterous population: Head capsule width ♂ 3.72mm , ♀ 4.32- 4.38mm; pronotal width ♂ 3.00mm, ♀ 3.90mm ; body length ♂ 20.4, ♀ 24.3mm ( Table 1 ). Color and pigmentation, lacinia, and dorsomesal band of erect white hairs similar to Iceberg Creek , Montana , population (described below) ( Figs. 17 , 23 , 29 , 35 , 41 , 47 , 53 ). Wingpads of ♂ ( Fig. 76 ) and ♀ macropterous. Gill number and arrangement typical of genus. Submental gill ( Fig. 66 ) length ♂ 0.54-0.57mm , ♀ 0.66-0.72mm ; anterior supracoxal gill ( Fig. 67 ) length ♂ 0.36mm , ♀ ( Fig. 68 ) 0.60-0.66mm ( Table 1 ). Legs with typical setation of genus as described by Stewart & Stark (2002) . Y-arms of mesosternum typical of genus. Cercal segments ♂ 26 ( Table 1 ), with setation typical of genus. Developing membranous windsock-like process of male epiproct evident in late instar individuals, and pointed posteroventrally in lateral view like the Iceberg Creek, Montana , population below ( Figs. 73 , 82 ). Developing female subgenital plate of 8 th sternum shallowly notched mesally like Glacier Creek population below ( Fig. 87 ). Figs. 60-69. Megarcys larval characters. 60. M. irregularis gills, male, Nisqually River, Washington. 61. M. signata gills, male, Mosquito Creek, Colorado. (SM = submental gill, ASc = anterior supracoxal gill, AT 2 = anterior mesothoracic gill, AT 3 = anterior metathoracic gill). 62. M. subtruncata male gills, Butte Creek, California. 63. M. subtruncata submentum and gills, male, Quinn Spring, Oregon. 64. M. subtruncata submentum and gills, female, Quinn Spring, Oregon. 65. M. watertoni gills, male, Iceberg Creek, Montana. 66. M. watertoni submental gill, male, Bear Creek/confl. Flathead River, Montana. 67. M. watertoni anterior supracoxal gill, male, Bear Creek/confl. Flathead River, Montana. 68. M. watertoni anterior supracoxal gill, female, Bear Creek/confluence Flathead River, Montana. 69. M. yosemite gills, male, Cold Creek, California. Scale lines = 2 mm. Figs. 70-74. Megarcys larval characters. 70. M. irregularis developing male genitalia, dorsal, Nisqually River, Washington 71. M. signata developing male genitalia, Mosquito Creek, Colorado. 72. M. subtruncata developing male genitalia, dorsal, Butte Creek, California. 73. M. watertoni developing male genitalia, dorsal, Iceberg Creek, Montana. 74. M. yosemite developing male genitalia, dorsal, Cold Water Creek, California. Scale line= 2mm. Figs. 75-83. Megarcys larval characters. 75. M. watertoni wingpads, male, Iceberg Creek, Montana. 76. M. watertoni wingpads, male, Bear Creek confl. Flathead River, Montana. 77. M. watertoni female wingpads, Iceberg Creek, Mt. 78. M. yosemite wingpads, male Cold Creek, California. 79. M. irregularis developing male genitalia, oblique view, Nisqually River, Washington. 80. M. signata developing male genitalia, lateral, Mosquito Creek, Colorado. 81. M. subtruncata developing male genitalia, oblique view, Butte Creek, California. 82. M. watertoni developing male genitalia, oblique view, Iceberg Creek, Montana. 83. M. yosemite developing male genitalia, oblique view, Cold Water Creek, California. Scale line = 2 mm. Iceberg Creek, Montana , male brachypterous (female macropterous) population: Head capsule width ♂ 2.76-3.00mm, ♀ 3.48-3.84mm ; pronotal width ♂ 2.58-2.64mm , ♀ 3.36mm ; body length ♂ 16.08-17.28mm , ♀ 20.9-22.2mm ( Table 1 ). Color and pigmentation (Figs, 17, 29, 35, 41, 47, 53), lacinia, ( Fig. 23 ), and dorsomesal band of erect silky white hairs typical of genus. Wingpads ♂ ( Fig. 75 ) brachypterous, ♀ ( Fig. 29 ) macropterous. Gill number and arrangement ( Fig. 65 ) typical of genus. Submental gill length ♂ 0.24-0.27mm , ♀ 0.36- 0.39mm; anterior supracoxal gill length ♂ 0.24- 0.27mm, ♀ 0.33-0.42mm ( Table 1 . Legs ( Fig. 35 ) with typical setation of genus. Y-arms of mesosternum ( Fig. 41 ) typical of genus. Cercal segments ♂ 26 ( Table 1 ), with setation typical of genus. Developing membranous windsock-like process of male epiproct ( Fig. 73 ) evident in late instar individuals, and pointed posteroventrally in lateral view ( Fig. 82 ). Developing female subgenital plate of 8 th sternum ( Fig. 87 ) shallowly notched mesally. Comments. The high elevation Iceberg Creek population was similar in color and pigmentation, and other generic characters, to the lower elevation Bear Creek population, except for male brachyptery and smaller body and gill sizes. Head capsule widths of males and females were on average 21.4% and 17.8%, respectively, smaller; pronotal widths of males and females were on average 13.0% and 13.8% smaller, and body lengths were on average 10.0% and 11.4% smaller ( Table 1 ). Gill lengths were substantially smaller; submental gills of males and females were on average 54.1% and 45.7% shorter; anterior supracoxal gills of males and females were on average 29.2% and 40.5% shorter, respectively ( Table 1 ).