Isoperla laucki Baumann & Lee

Sandberg, John B., 2011, The Isoperla Of California (Plecoptera: Perlodidae); Larval Descriptions And A Key To 17 Western Nearctic Species, Illiesia 7 (22), pp. 202-258 : 227-229

Isoperla laucki Baumann & Lee

( Figs. 2g , 9 a-h, 20g)

Isoperla laucki Baumann & Lee 2009 , 5:2-5. ♂, ♀, larva (reared), ovum.

Material examined. CALIFORNIA: Humboldt Co., Dragsaw Spring, FR 13N02 crossing, 12-13/VII/2009, 10-12/VII/2010, J. Sandberg, Larvae (reared).

Male larva. Body length of mature larva 9–10 mm. Dorsum of head with contrasting pigment pattern and fine dark clothing setae, anterior frontoclypeus margin unpigmented; light M shaped pattern anterior to median ocellus a distinct thin band, not connected to light frontoclypeus area, median longitudinal light band absent, lateral thin arms directed posterolaterally, extending to antennal bases; posterior ocelli with completely enclosed small light areas along outer lateral margins; interocellar area entirely dark; occiput with irregular spinulae band extending from below eye to near median epicranial suture, usually enclosed completely by dark pigment ( Fig. 9a ). Lacinia bidentate, total length 839–938 µm ( Figs. 2g , 9e- h , Tables 2-4 ); submarginal row (A+B) with 4 setae, groups A-B interrupted by gap below subapical tooth (SAT) inner margin ( Fig. 9g ); 1–2 submarginal setae (A), the first located at base of apical tooth (AT) inner margin, the second when present, located between the AT and SAT inner margins, shorter and half as stout at base than first, plus 1 thin marginal seta (TMS) adjacent to AT inner margin, sometimes obstructed from view by AT, submarginal seta (A) or broken, and 1 dorsal seta (DS) located below SAT inner margin, partially obstructed by SAT ( Figs. 9 gh); 2–3 submarginal setae (B) located past SAT inner margin ( Fig. 9h ); 7–9 marginal setae (C), initially long-stout and widely spaced, last few shorter and widely spaced, blending into and difficult to differentiate from dorsal surface setae ( Fig. 9e ); 8–13 ventral surface setae (D) scattered below marginal setae, ending posteriorly at approximately ¾ the inner lacinia margin length, mostly concentrated in posterior half ( Fig. 9f ); dorsal surface setae (DSS) continue from last marginal setae (C) as a single, laterally protruding, submarginal row (sometimes 2– 3 setae thick) along inner-lateral margin, ending before posterior-most ventral surface setae ( Fig. 9f ). Galea with 28–44 setae in thick ventral band, apex with 4–7 setae. Maxillary Palp segments 2–3 with curved, apically pointed setae. Pronotum with thin median light line bordered by irregular dark longitudinal bands with adjacent light rugosites; discs each with dark comma shaped lateral areas, fine dark clothing setae restricted to areas of dark pigmentation and lateral margins without broad light bands ( Fig. 9b ). Meso and metanotum with contrasting pigment pattern and fine dark clothing setae ( Fig. 9c ). Legs with numerous fine golden clothing setae and scattered erect spines on outer surface of femora, erect spines longest and concentrated on dorsal surface; fine silky setae sparse on dorsal surfaces of femora and tibia ( Fig. 20g ); tibia with faint transverse bands near proximal end. Abdominal terga without distinct longitudinal dark stripes; tergites marked with a close set pair of dorsal small light spots and a wide set triplet of light spots laterally; numerous fine dark clothing setae and erect spines scattered dorsally; posterior margin with scattered long and numerous short spines in a concentrated row ( Fig. 9d ).

Distribution. Known only from four Humboldt County streams (Bauman & Lee 2009).

Diagnosis. Male larvae of I. laucki can be distinguished from other western Isoperla species with 1–2 submarginal setae (A) by the presence of 8– 13 ventral lacinia surface setae ( Figs 9 e-h), fine silky setae sparse on dorsal surfaces of femora and tibia, the interocellar area completely dark ( Fig. 9a ), and abdomen lacking longitudinal stripes ( Fig. 9d ). This species is most similar to I. adunca ( Figs. 4 a-h & 20b) in that it lacks abdominal stripes ( Fig. 9d ), but can be separated by the interrupted lacinia submarginal setae row ( Fig. 9g ).

Remarks. This species was the only Isoperla species in four Humboldt County spring fed streams ( Baumann & Lee 2009).

Figures

Figs. 2a-q. Isoperla lacinia habitus, 40x, Bar = 500µm. 2a. I. acula; 2b. I. adunca; 2c. I. baumanni; 2d. I. bifurcata; 2e. I. denningi; 2f. I. fulva; 2g. I. laucki; 2h. I. marmorata; 2i. I. miwok; 2j. I. mormona; 2k. I. muir; 2L. I. pinta; 2m. I. quinquepunctata; 2n. I. roguensis; 2o. I. sobria; 2p. I. sordida; 2q. I. tilasqua.

Figs. 9a-h. Isoperla laucki nymph and ventral maxilla, Dragsaw Spring, Humboldt County, CA. Submarginal setae groups A and B, Marginal setae C, Ventral surface setae D, Dorsal surface setae DSS, Dorsal seta DS, and Thin marginal seta TMS. White bars = 1 mm, 9e-f 100x, 9g 200x, and 9h 400x.

Figs. 20a-q. Isoperla front right leg habitus, Larvae, 32–40x, Bar = 1mm. 20a. I. acula; 20b. I. adunca; 20c. I. baumanni; 20d. I. bifurcata; 20e. I. denningi; 20f. I. fulva; 20g. I. laucki; 20h. I. marmorata; 20i. I. miwok; 20j. I. mormona; 20k. I. muir; 20L. I. pinta; 20m. I. quinquepunctata; 20n. I. roguensis; 20o. I. sobria; 20p. I. sordida; 20q. I. tilasqua.

Figs. 4a-h. Isoperla adunca nymph and ventral maxilla, Campbell Creek, Butte County, CA. Submarginal setae groups A and B, Marginal setae C, and Ventral surface setae D. White bars = 1 mm, 4e-f 100x, 4g 200x, and 4h 400x.