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 irregularis ( Banks 1900 ) ( Figs. 12 , 24 , 30 , 36 , 42 , 48 , 60 , 70 , 84 a-b, Table 1 ) Distribution. Pacific Northwest; Coastal and Cascade Mountains of Washington , British Columbia. Material examined. Washington : Pierce Co. , Fryingpan Creek , Sunrise Road , Mount Rainier National Park , 13-VII-2003 , B. Kondratieff, J. Schmidt, 1♂ , 2♀ larvae; 14-VII-2004 , B. Kondratieff, 5♀ ; Nisqually River , Longmire , Mount Rainier National Park , 28-V-1997 , B. Kondratieff , 2♂ , 1♀ , 2♂ larvae; White River , Hwy. 410, Mount Rainier National Park , B. Kondratieff , 8♂ , 1♀ , 3♂ larvae, 3♀ larvae, 1♂ exuvium, 2♀ exuviae; 20-VI-2003 , B. Kondratieff , R . Zuellig, J . Schmidt , 2♀ . Figs. 3-11. Megarcys signata larval characters. 3. Head-pronotum. 4. Left lacinia, ventral. 5. Left mandible, ventral. 6. Right front leg, dorsal. 7. Mesosternum. 8. Gill arrangement, ventral. 9. Male abdomen, ventral. 10. Female abdomen, ventral. 11. Basal-mid-apical cercomeres, dorsal. ( Stewart & Stark 2002 , Figs. 14.36 a-i). Figs. 12-17. Megarcys larval head-pronotal pattern. 12. M. irregularis , White River , Washington. 13. M. signata, Mosquito Creek , Colorado. 14. M. subtruncata, Ohanopecosh River , Washington. 15. M. subtruncata , Butte Creek , California. 16. M. subtruncata, Quinn Spring , Oregon. 17. M. watertoni , Iceberg Creek , Montana. Characters. Head capsule width ♂ 3.06-3.30mm , ♀ 3.90-4.62mm ; pronotal width ♂ 2.88-3.12mm , ♀ 3.36- 4.08mm; body length ♂ 18.3-19.5mm , ♀ 19.5-24.0mm ( Table 1 ). Color and pigmentation ( Figs. 12 , 24 , 30 , 36 , 42 , 48 ), lacinia, and dorsomesal band of erect silky white hairs typical of genus. Wingpads of ♂ and ♀ macropterous. Gill number and arrangement typical of genus ( Fig. 70 ). Submental gill length ♂ 0.12- 0.42mm, ♀ 0.36-0.45mm ; anterior supracoxal gill length ♂ 0.27-0.42mm , ♀ 0.36mm ( Table 1 ). Legs ( Fig. 30 ) with setation typical of genus as described by Stewart & Stark (2002) .Y-arms of mesosternum ( Fig. 36 ) typical of genus. Cercal segments ♂ 24-26 ( Table 1 ), with setation typical of genus. Developing membranous, windsocklike process of male epiproct ( Figs. 42 , 48 , 70 ) evident in late instar individuals, and pointed posteroventrally in lateral view ( Fig. 79 ).Developing female subgenital plate of 8 th sternum ( Figs. 49 , 84a, b ) shallowly notched mesally. Figs. 18-23. Megarcys larval characters. 18. M. signata , thorax, lateral, Mosquito Creek, Colorado. 19. M. signata , abdomen, lateral, Mosquito Creek, Colorado 20. M. subtruncata , thorax-abdomen, lateral, Quinn Spring, Oregon. 21. M. signata , right lacinia, ventral, Mosquito Creek, Colorado. 22. M. subtruncata , right lacinia, ventral, Ohanapecosh River, Washington. 23. M. watertoni , right lacinia, ventral, Iceberg Creek, Montana. Comments. The generic characters proposed by Stewart & Stark (2002) , based solely on M. signata , are reaffirmed in this species, and color and pigmentation fit the generic pattern illustrated herein for M. signata . The measured gill lengths and shapes were greatly variable in this species ( Table 1 ), and otherwise similar to M. signata .