Stewart, K.W. & B.C. Kondratieff. 2012. Larvae of the Nearctic species of the stonefly genus Megarcys Klapálek (Plecoptera: Perlodidae). Illiesia, 8(03):16-36. Available online: http://www2.pms-lj.si/illiesia/papers/Illiesia08-03.pdf LARVAE OF THE NEARCTIC SPECIES OF THE STONEFLY GENUS MEGARCYS KLAPÁLEK (PLECOPTERA: PERLODIDAE) Kenneth W. Stewart1 and Boris C. Kondratieff2 1 Department of Biological Sciences, P.O. Box 305220, University of North Texas, Denton, Texas, U.S.A.76203 E-mail:
[email protected] 2 Department of Bioagricultural Sciences and Pest Management, Colorado State University, Fort Collins, Colorado, U.S.A. 80523 E-mail:
[email protected] ABSTRACT Associated larvae of the five Nearctic species of Megarcys are comparatively described and illustrated. Four of them, Megarcys irregularis Banks, M. subtruncata Hanson, M. watertoni (Ricker), and M. yosemite (Needham & Claassen) are described in detail for the first time. Body size and setation, wingpad macroptery/brachyptery, and gill size were variable between populations of some species. Diagnostic differences were not found in late instar larvae of the five species in color and pigment patterns, mouthparts, body and appendage setation, gill size and structure, and developing male and female genitalia. The detailed descriptions and measurements help expand the generic diagnosis, show morphological differences between populations of different habitats, and provide an atlas of illustrations for larvae of the five species. Keywords: Plecoptera, stonefly larvae, Megarcys, Nearctic INTRODUCTION and M. teslenkonis Zwick 2010, remain unknown. The stonefly genus Megarcys Klapálek 1912, VanWieren et.al. (2001) reviewed and presented comprises seven Palearctic and five Nearctic species new updated and detailed descriptions and (DeWalt et al.