Megarcys subtruncata Hanson 1942

Stewart, Kenneth W. & Kondratieff, Boris C., 2012, Larvae Of The Nearctic Species Of The Stonefly Genus Megarcys Klapálek (Plecoptera: Perlodidae), Illiesia 8 (3), pp. 16-36 : 23-27

publication ID	https://doi.org/ 10.5281/zenodo.4760667
DOI	https://doi.org/10.5281/zenodo.4765813
persistent identifier	https://treatment.plazi.org/id/C250BC3D-FFBF-FF97-FEBC-3C23FE3C40C0
treatment provided by	Felipe
scientific name	Megarcys subtruncata Hanson 1942
status

Treatment

Megarcys subtruncata Hanson 1942 View in CoL

( Figs. 14-16 View Figs , 20, 22 View Figs , 26-28 View Figs , 32-34 View Figs , 38-40 View Figs , 44-46 View Figs , 51, 52 View Figs , 62-64 View Figs , 72 View Figs , 81 View Figs , 86 View Figs , Table 1 View Table 1 )

Distribution. California, Pacific Northwest (Oregon, Washington, British Columbia), and Northern Rocky Mountains (Idaho, Montana).

Material examined. California: Butte Co., Butte Creek, Cherry Hill Campground, 12-V-2007, J. Sandberg, 1♂, 5 ♂ larvae, 5♀ larvae. Shasta Co., Hat Creek at Hat Creek Lake, Lassen-Volcanic National Park, 6-VII-1979, K. Stewart, B. Stark, 1 reared ♀, 1 pharate ♂ larva (cleared genitalia), 1♀ larva; Hat Creek, Big Pine Camp, 26-IV-1987, B. Stark, R. Baumann, C. Nelson, 1♂ larva. Oregon: Deschutes Co., Quinn River Spring, Quinn River Campground, 10-VI-2004, B. Stark, R. Baumann, 20♂, 13♀, 8♂ larvae, 8♀ larvae. Washington: Lewis Co., Ohanapecosh River, Grove of the Patriarchs, Mount Rainier National Park, 28-V-1997, B. Kondratieff, 1 reared ♂ with exuvium; Ohanapecosh River, Hwy. 123, North Silver Falls, Mount Rainier National Park, 23-V-2003, B. Kondratieff, J. Schmidt, R. Evans, 2♂ larvae, 4♀ larvae; Ohanapecosh River, Hwy. 123, Paradise River above Narada Falls, Mount Rainier National Park, 16-VIII-1999, B. Kondratieff, R. Lechleitner, 1♀, 2 reared ♀ with exuviae, 5 exuviae; Pierce Co., Fish Creek, Westside Road Bridge, Mount Rainier National Park, 21-VI-2003, B. Kondratieff, R. Zuellig, J. Schmidt, 2♂, 1♀, 1♂ exuvium, 2♀ exuviae; Fryingpan Creek, Sunrise Road, Mount Rainier National Park, 16-VIII-1999, B. Kondratieff, 1♂ with exuvium, 1♀ with 2 exuviae; Ipsut Creek at bridge, Mount Rainier National Park, 6-VI-1997, R. Lechleitner, 2♀, 1 exuvium.

Characters. Butte Creek, California, macropterous population: Head capsule width ♂ 3.78-3.90mm, ♀ 4.68-4.74mm; pronotal width ♂ 3.36-4.48mm, ♀ 4.20mm; body length ♂ 17.9-21.6mm, ♀ 22.2-25.5mm ( Table 1 View Table 1 ). Color and pigmentation ( Figs. 15 View Figs , 27 View Figs , 33 View Figs , 39 View Figs , 45 View Figs , 51 View Figs ), lacinia (like Ohanapecosh River, Washington population Fig. 28 View Figs ), and dorsomesal band of erect silky white hairs typical of genus. Wingpads of ♂ ( Fig. 27 View Figs ) and ♀ macropterous. Gill number and arrangement typical of genus ( Fig. 62 View Figs ). Submental gill length ♂ 0.39-0.54mm, ♀ 0.54- 0.66mm; anterior supracoxal gill length ♂ 0.42- 0.54mm, ♀ 0.54-0.66mm ( Table 1 View Table 1 ). Legs ( Fig. 33 View Figs ) with typical setation of genus as described by Stewart & Stark (2002). Y-arms of mesosternum ( Fig. 39 View Figs ) typical of genus. Cercal segments ♂ 24-26 ( Table 1 View Table 1 ), with setation typical of genus. Developing membranous windsock-like process of male epiproct ( Fig. 72 View Figs ) evident in late instar individuals, and pointed posteroventrally in lateral view ( Fig. 81 View Figs ). Developing female subgenital plate of 8 th sternum ( Figs. 51 View Figs , 86 View Figs ) shallowly notched mesally.

Quinn Spring, Oregon, brachypterous population: As indicated by Stark & Baumann (2005), larvae of this population, that they did not describe in detail, “agree in most respects” with the generic description in Stewart & Stark (2002). Head capsule width ♂ 3.12-3.48mm, ♀ 4.20-4.22mm; pronotal width ♂ 2.94- 3.12mm, ♀ 4.02-4.26mm; body length ♂ 15.6-16.0mm, ♀ 19.5-21.2mm. Color and pigmentation ( Figs. 16 View Figs , 28 View Figs , 34 View Figs , 40 View Figs , 46 View Figs ), lacinia typical of genus. Dorsomesal band of erect silky white hairs and those along the ecdysial suture of the head absent. Wingpads ♂ ( Fig. 28 View Figs ) and female brachypterous. Gill number and arrangement typical of genus. Submental gill ( Fig. 63 View Figs ) length ♂ 0.27-0.30mm, ♀ ( Fig. 64 View Figs ) 0.34-0.36mm; anterior supracoxal gill length ♂ 0.21-0.24mm, ♀ 0.30-0.34mm ( Table 1 View Table 1 ). Legs ( Fig. 34 View Figs ) with typical setation of genus. Y-arms of mesosternum ( Fig. 40 View Figs ) typical of genus. Cercal segments of ♂ 22+ (all broken), dorsal silky fringe (typical of the other four species) absent or with a few obscure setae on basal segments. Developing membranous, windsock-like process of male epiproct evident in late instar individuals, and pointed posteroventrally in lateral view like the Butte Creek, California, population ( Fig. 81 View Figs ). Developing female subgenital plate of 8 th sternum shallowly notched mesally like the Butte Creek, California, population ( Figs. 51 View Figs , 86 View Figs ).

Comments. The Quinn Spring, Oregon, brachypterous population exhibited these substantial character differences from generic and the Butte Creek, California, and Ohanapecosh River, Washington macropterous populations examined: 1) the dorsomesal band of erect silky white hairs and those along the ecdysial suture of the head were absent, 2) the dorsal silky fringe of basal cercal segments was absent or with only a few obscure setae present, 3) the body size (length) of pre-emergent males was on average 20% shorter, and females about 15% shorter ( Table 1 View Table 1 ), 4) submental and anterior supracoxal gills of males ( Fig. 63 View Figs ) were on average about 39% and 53% shorter, respectively ( Table 1 View Table 1 ). The gills of the Quinn Spring population could therefore generally be described as “short” in comparison with “long” in the other two populations studied. This suggests that populations of this species in ecotypes may vary in wing length, body and gill size, and setation, but still conform to the diagnostic generic characters of gill arrangement and Y-arms extending to anterior corners of the furcal pits ( Stewart & Stark 2002).