Stonefly Species Megarcys watertoni (Glacier Springflies)

Source: Larvae Of The Nearctic Species Of The Stonefly Genus Megarcys Klapálek (Plecoptera: Perlodidae)

(Figs. 17, 23, 29, 35, 41, 47, 53, 65 - 68, 73, 75 - 77, 82, 87, Table 1)Source: Larvae Of The Nearctic Species Of The Stonefly Genus Megarcys Klapálek (Plecoptera: Perlodidae)

Characters. Bear Creek, Montana, macropterous population: Head capsule width male 3.72 mm, female 4.32 - 4.38 mm; pronotal width male 3.00 mm, female 3.90 mm; body length male 20.4, female 24.3 mm (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). Wing pads of male (Fig. 76) and female macropterous. Gill number and arrangement typical of genus. Submental gill (Fig. 66) length male 0.54 - 0.57 mm, female 0.66 - 0.72 mm; anterior supracoxal gill (Fig. 67) length male 0.36 mm, female (Fig. 68) 0.60 - 0.66 mm (Table 1). Legs with typical setation of genus as described by Stewart & Stark (2002). Y-arms of mesosternum typical of genus. Cercal segments male 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).

Iceberg Creek, Montana, male brachypterous (female macropterous) population: Head capsule width male 2.76 - 3.00 mm, female 3.48 - 3.84 mm; pronotal width male 2.58 - 2.64 mm, female 3.36 mm; body length male 16.08 - 17.28 mm, female 20.9 - 22.2 mm (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. Wing pads male (Fig. 75) brachypterous, female (Fig. 29) macropterous. Gill number and arrangement (Fig. 65) typical of genus. Submental gill length male 0.24 - 0.27 mm, female 0.36 - 0.39 mm; anterior supracoxal gill length male 0.24 - 0.27 mm, female 0.33 - 0.42 mm (Table 1. Legs (Fig. 35) with typical setation of genus. Y-arms of mesosternum (Fig. 41) typical of genus. Cercal segments male 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.