Cosumnoperla sequoia, Bottorff, 2007

Bottorff, Richard L., 2007, Cosumnoperla Sequoia, A New Species Of Stonefly From The Sierra Nevada, California (Plecoptera: Perlodidae: Isoperlinae), Illiesia 3 (6), pp. 46-52 : 46-51

Cosumnoperla sequoia , sp. n.

( Figs. 1‐12 )

Material examined. Holotype ♂, allotype ♀, and 4♂, 3♀, and 7 larval paratypes from the United States, California, Fresno County, unnamed intermittent creek (Latitude 36 ° 48.772’ N, Longitude 118 ° 50.122’ W, Elevation 1050 m), west of Redwood Creek , 10 mi [16 km] west of Cedar Grove , Sequoia National Forest , 5 June 1990, R. L. Bottorff (Holotype and allotype USNM, paratypes USNM, RLB). Additional paratypes: USA, California, Fresno County : Lockwood Creek at Hwy 180 (Elevation 1000 m), 8 mi [13 km] NE Wilsonia, Sequoia National Forest, 5 June 1990 (1♂), R. L. Bottorff ( RLB); Kings Canyon Road, waterfall at 3,500’ [1067 m], 31 May 1963 (1♂), C. P. Alexander ( USNM); Kings Canyon, Rt. 180, waterfall above Horseshoe Bend, 3,500’ [1067 m], 1 June 1963 (2♂, 2♀), C. P. Alexander ( USNM).

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Male. Body uniform brown, length 8.1‐9.0 mm. Head brown, width 1.9‐2.0 mm (measured to outside margins of compound eyes), dark M‐ shaped mark anterior to median ocellus, interocellar area darker brown ( Fig. 1 ). Pronotum uniform brown, anterior corners darker, lateral edges white, disks with rugosities. Macropterous, forewing length 7.1‐7.8 mm, most wing cells and veins dark brown, costa and subcosta veins white, cells between costa and radius white. Supra‐ anal process bulbous and membranous. Paraprocts reduced and lightly sclerotized, lying under supra‐ anal process. Tergum 9 and 8 with medial and bipartite elevated patches (respectively) of dense stout golden spinulae ( Figs. 2, 3 ). Tergum 10 posterior margin with a shallow median notch (slightly wider in some specimens, Fig. 4 ); reflexed narrow process bearing two pairs of stout spines, the anterior pair pointing forward, the posterior pair pointing dorsally; fine stiff golden setae densely covering reflexed process (not shown in drawings). Aedeagus spherical with bulbous apex and lateral basal folds; small median cavity or indention on posterior surface (this may be a narrow invaginated lobe that failed to extend when the aedeagus was extruded); posterior and lateral band of dense unpigmented stout spinulae, posterior and lateral patches of medium golden spinulae at base of aedeagus, anterior medial patch of long golden spinulae ( Fig. 5 ). Basal cercal segments (1‐5) densely covered with stiff golden setae, these most abundant on the mesal and dorsal surfaces. Vesicle absent.

Female. Body coloration and general appearance similar to male, but of larger size (body length 8.512.6 mm, head width 2.2‐2.6 mm). Macropterous, forewing length 8.6‐10.4 mm. Subgenital plate elongated, nearly reaching posterior margin of 10 th sternum, width narrowing from base to a shallowly notched apex, lateral sides irregularly indented, plate projecting ventrally from body axis ( Figs. 6a,b, c ).

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6a 6c

Egg. Oblong (circular cross‐ section). Length 700 μm. Width 400 μm. Color olive green. Collar and eclosion line absent. Chorion covered with irregular quadrangular or hexagonal follicle cell impressions (FCIs) bordered by raised walls, FCI floors flat. Each FCI typically surrounded by 6 other FCIs (range, 5‐7). Micropyles not seen. Egg microstructure similar to that of C. hypocrena (see Figures 20‐21 in Szczytko & Bottorff 1987).

Larva. General body color medium brown; pigment pattern similar to that of C. hypocrena (Szczytko & Bottorff 1987; Stewart & Stark 2002). Body length of mature larvae, 11.1 mm male and 11.3‐13.8 mm female. Head width 1.8‐2.4 mm. Head mostly brown, with light M‐ shaped mark anterior to median ocellus, ocellar triangle with a median oval white spot, rectangular white spots lateral to ocellar triangle, occiput with reticulate light patches and an irregular row of spinules ( Fig. 7 ). Mandibles with 6 teeth, 5 th tooth serrated; marginal brush of long stiff setae; tuft of marginal bristles below 4 th tooth (dense and expanded on left mandible, sparse on right mandible); ventral sparse setal patch extending from 1 st tooth to mandible base ( Figs. 15a, b ). Lacinia with 2 large teeth; apical tooth about twice as long as the subapical tooth; 4‐6 setae between apical and subapical teeth; lacinial margin below subapical tooth with 6‐8 stout setae and then 10‐12 thin setae, sub‐ marginal row of 4‐6 stout setae ( Fig. 16 ). Pronotum with brown disks and white rugosities, lateral margins white. All thoracic sterna with distinct medial sclerites covering and extending beyond furcal pits ( Fig. 8 ). Prosternal sclerite extends forward from furcal pits to anterior margin of prosternum, sclerite swollen in mid‐ segment and then narrowed anteriorly. Mesosternal Y‐ arms meet posterior corners of furcal pits, transverse suture connects anterior corners of furcal pits; sclerite extends laterally beyond Y‐ arms, lateral margin irregular or sinuous. Gills absent. Femora and tibia with dense short setae, scattered spinules, and fringed with light silky hairs ( Fig. 9 ). Abdominal terga brown, most segments with a pair of large submedial and lateral light spots (overall, gives the appearance of longitudinal light and dark striping); each tergum with a transverse row of 6 dark dots, 2 mesally and 2 each laterally ( Fig. 10 ). Posterior margin of male abdominal sterna 8 and 9 entire, with a continuous setal row ( Fig. 11 ). Posterior margin of female abdominal sternum 8 sclerotized medially and slightly protruding, with a median setal gap ( Fig. 12 ). Cercal segments with a posterior whorl of short setae, dorsal fringe of long hairs absent.

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Diagnosis. Cosumnoperla sequoia shares several diagnostic features with C. hypocrena . Adult males of both species have (1) a reflexed process with an anterior pair of prominent spines on the 10 th tergum, (2) a median patch of stout spinulae on the 9 th tergum, (3) a membranous aedeagus, (4) a bulbous membranous supra‐ anal process, (5) weakly sclerotized flat paraprocts, and (6) vesicle absent. Adult females have an extended apically‐ notched subgenital plate. Larvae of both species have (1) abdominal longitudinal stripes and dark dots and (2) a sinuate mesosternal sclerite that extends laterally beyond the Y‐ arms. Eggs have a punctuate microstructure and are large, green, oblong, and collarless. Both species are restricted to intermittent streams in the Sierra Nevada, California.

Cosumnoperla sequoia adults and larvae differ from C. hypocrena by their smaller size and several morphological features: (1) adult pronotum – C. sequoia uniform brown, lateral margins white; C. hypocrena median light stripe, (2) wings – C. sequoia uniform dark brown except for white cells and veins between costa and radius; C. hypocrena cells and veins uniform dark brown, (3) 10 th tergum of male adults – C. sequoia narrow reflexed process with mesoposterior notch and two posterior spines; C. hypocrena broad reflexed triangular process with mesoposterior entire and posterior spines absent ( Figs. 13, 14 ), (4) terga 8 and 9 of male adults – C. sequoia prominent swollen patches of golden stout spinulae; C. hypocrena small unswollen patch of spinulae on 9 th tergum, few spinulae on 8 th tergum ( Figs. 13, 14 ), (5) basal cercal segments of male adults – C. sequoia dense long setae; C. hypocrena sparse long setae, (6) subgenital plate of female adults – C. sequoia long and narrow with irregular sides and shallow apical notch; C. hypocrena short and broad with smooth sides and deep apical notch, (7) prosternal sclerite of larvae ‐ C. sequoia swollen anterior to furcal pits; C. hypocrena uniformly narrow anterior to furcal pits. The oblong collarless green egg of C. sequoia is slightly smaller than that of C. hypocrena , but both eggs have similar microstructure and are some of the largest stonefly eggs reported.

Several characters clearly place Cosumnoperla sequoia within the Isoperlinae – (1) smaller adult size than most Perlodinae, (2) reduced membranous supra‐ anal process, (3) simple unsclerotized paraprocts of male adults, (4) uncleft 10 th tergum of male adults, (5) larvae with longitudinal abdominal stripes, and (6) larval submental and thoracic gills absent. Adult males of Isoperlinae often have various spinulae patches, dorsal swellings, or modifications of the 9 th and 10 th terga. Although not all characters clearly separate the Isoperlinae from Perlodinae, the preponderance of traits do distinguish these two subfamilies. Cosumnoperla and the monotypic Isoperlinae genera may be transitional forms between the Perlodinae and Isoperla since they share some characters with both taxonomic groups. In contrast with Isoperla , the adult males of Cosumnoperla and the monotypic Isoperlinae genera have various processes, lobes, ridges, or recurved hooks on tergum 10 and lightly sclerotized paraprocts. Within the Nearctic Isoperlinae, only Cosumnoperla sequoia , Clioperla clio , and Cascadoperla trictura have slightly to deeply notched 10 th terga.

Etymology. This species is named after the type locality, which is near the impressive groves of Sequoia big trees ( Sequoiadendron giganteum ) and Sequoia National Park.

Distribution. This species is presently known from the type locality and a nearby creek in the southern Sierra Nevada, California.

Biological Notes. When the holotype and allotype of C. sequoia were collected in 1990, the type locality stream was dry, except at one location where a small trickle of water seeped down the vertical face of a granite bedrock cliff (10 m) and temporarily collected in a small shallow pool (1 m diameter) at the base, before sinking into the channel substrate. Mature larvae inhabited this one pool (water temperature, 16.3 ° C) and adults were collected on nearby vegetation. Obviously, these stoneflies were collected at the very end of the normal winter‐ spring flow period of this intermittent stream. Cosumnoperla sequoia was absent from a nearby perennial stream, Redwood Creek, which instead had a typical assemblage of Sierra stoneflies, including some semivoltine Perlidae . The distributions of C. sequoia and C. hypocrena are confined to intermittent streams at low to medium elevations (300‐1500 m) of the Sierra Nevada. Based upon presently known distributions, these two species are separated by about 250 km along this mountain range.

Figures

Figs. 1‐5. Cosumnoperla sequoia adult male. 1. Head‐pronotum, dorsal; 2. Terminalia (segments 8‐10, abdomen extended), dorsal; 3. Terminalia (segments 8‐10, abdomen contracted), right lateral; 4. Variant of reflexed process, 10th tergum, dorsal; 5. Aedeagus, right lateral (arrow shows location of median indention); Scale lines = 0.5 mm.

Fig. 6. Cosumnoperla sequoia adult female. 6a. Terminalia (segments 8‐10), ventral; 6b‐c. Variants of subgenital plate, ventral; Scale lines = 0.5 mm.

Figs. 7‐12. Cosumnoperla sequoia larva. 7. Head‐pronotum, dorsal; 8. Thorax, ventral; 9. Right front leg, dorsal; 10. Abdomen (segments 1‐10), dorsal; 11. Male terminalia (segments 8‐10), ventral; 12. Female terminalia (segments 8‐10), ventral; Scale lines = 0.5 mm.

Figs. 15‐16. Cosumnoperla sequoia larva. 15. Right (a) and left (b) mandibles, ventral; 16. Right lacinia, ventral.

Figs. 13‐14. Cosumnoperla hypocrena adult male. 13. Terminalia (segments 9‐10), dorsal; 14. Terminalia (segments 9‐10), right lateral; Scale lines = 0.5 mm.