Podmosta delicatula (Claassen)

Stewart, Kenneth W. & Stark, Bill P., 2011, Further Descriptions Of Western North American Podmosta Larvae And Their Separation From Ostrocerca Larvae (Plecoptera: Nemouridae), Illiesia 7 (10), pp. 104-117 : 110

Podmosta delicatula (Claassen)

( Figs. 2, 3, 5, 9-12 , 17 , 30 , 45, 46 )

Distribution. Widespread in Rocky Mountains, Great Basin, Pacific Northwest (New Mexico, Nevada and California, northwestward to Alaska).

Material examined. Colorado: Larimer Co., Buckhorn Creek, 32 km north of Masonville , 31-V-1986, B.C. Kondratieff, 2♂, 2♀, 1♂ larva, 3♀ larvae, 1 exuvium . Oregon: Umatilla Co., Meachum Creek and tributaries at and upstream of Hwy. 84 and adjacent railroad bridges, 26-IV-2004, K.W. Stewart, B.J. Armitage, 12♂ larvae, 17♀ larvae (121 adults, all P. delicatula , in Monte L. Bean Life Science Museum, Brigham Young University, collected at this site) .

Characters. Body length ♂ 4.2-4.5 mm, ♀ 4.3-5.5 mm, light brown above, with mottled dark head pattern, distinct light interocellar spot and light mesal stripe on thorax ( Fig. 2 ). Antennal segments approximately 38, head capsule width ♂ 0.78-0.88 mm, ♀ 0.84-0.96 mm; eyes large, head wider than pronotum ( Fig. 2 ). Gills absent. Mandibles with 5 or 6 apical teeth; right mandible with raised molar pad (as in other species) that grinds against opposing, depressed molar cup of left mandible ( Fig. 17 ) as in a “mortar- pestle” action, molar cup with outer (dorsal) comb of curved teeth ( Fig. 17 ). Lacinia triangular, palmate, with scalloped palm surface, similar to other species. Pronotum bearing short bristles and sensillae scattered over surface and lacking distinct lateral fringe ( Fig. 30 ). Metathoracic wingpads bearing short bristles scattered over surface, and tuft of short bristles on anterolateral corners. Femora bearing short bristles and hairs scattered over dorsal surface, longer bristles apicodorsally ( Fig. 3 ). Tibiae bearing scattered short bristles and few (5-8) posterior silky fringe hairs ( Fig. 3 ). Mesosternal Y-ridge faint, closed by an anterior ridge forming a rectangular area. Abdominal terga bearing microtrichia and socketed macrotrichia scattered over intercalary surface and forming a posterior fringe. Sexual dimorphism evident; males with developing hypoproct on sternum 9 ( Fig. 10 ) and in pharate individuals evidence of developing dorsal genitalia ( Figs. 9, 11 ). Cercal segments 22-24; cercomeres 1-10 bearing apical whorls of stout bristles, fine hairs and sensillae, bristles up to same length as their segment ( Fig. 45 ). Middle and anteapical cercomeres bearing long whorl bristles up to 0.60 times length of their segment, and 3-6 fine intercalary hairs up to 0.30 times length of their segment, ( Fig. 46 ) all as seen laterally. Diagnostic characters: light interocellar spot ( Fig. 2 ), and cercal setation as described ( Figs. 45, 46 ).

Figures

Figs. 2-16. Podmosta larval characters. P. delicatula. 2. head, thorax, dorsal. 3. right front leg, dorsal. 5. cercus, lateral. 9. male terminalia, dorsal. 10. male terminalia, ventral. 11. male terminalia, lateral. 12. female terminalia, dorsal. P. obscura. 4. right front leg, dorsal. 6. right cercus proximal segments, dorsal. 7. left cercus apical segments, lateral. 13. male terminalia, dorsal. 14. male terminalia, ventral. 15. male terminalia, lateral. 16. female terminalia, ventral. P. weberi. 8. right cercus, lateral (exuvium of reared male). 12a. male terminalia, ventral (exuvium of reared male).

Figs. 17-22. Podmosta mandibles. 17. P. delicatula left mandible, ventral. 18. P. obscura left mandible, ventral. 19. P. weberi right mandible, ventral. 20. P. weberi left mandible, ventral. 21. P. weberi right molar pad. 22. P. weberi left molar cup.

Figs. 29-34. Podmosta and Ostrocerca pronota. 29. P. decepta, right disc. 30. P. delicatula, right disc. 31. P. obscura right disc. 32. P. weberi left disc. 33. O. dimicki left disc. 34. O. dimicki left anterolateral disc margin.

Figs. 41-46. Podmosta and Ostrocerca abdomens and cerci. 41. P. weberi left abdominal terga 8-10. 42. O. dimicki left abdominal terga 8,9. 43. P. decepta cercomeres 9,10, lateral. 44. P. decepta cercomeres 20, 21, lateral. 45. P. delicatula proximal 7 cercomeres. 46. P. delicatula subapical cercomeres.