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

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Isoperla laucki Baumann & Lee


Isoperla laucki Baumann & Lee  

( Figs. 2g View Figs , 9 View Figs 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 View Figs ). Lacinia bidentate, total length 839–938 µm ( Figs. 2g View Figs , 9e- h View Figs , Tables 2-4 View Table 2 View Table 3 View Table 4 ); submarginal row (A+B) with 4 setae, groups A-B interrupted by gap below subapical tooth ( SAT) inner margin ( Fig. 9g View Figs ); 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 View Figs gh); 2–3 submarginal setae (B) located past SAT inner margin ( Fig. 9h View Figs ); 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 View Figs ); 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 View Figs ); 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 View Figs ). 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 View Figs ). Meso and metanotum with contrasting pigment pattern and fine dark clothing setae ( Fig. 9c View Figs ). 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 View Figs ); 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 View Figs ).

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 View Figs e-h), fine silky setae sparse on dorsal surfaces of femora and tibia, the interocellar area completely dark ( Fig. 9a View Figs ), and abdomen lacking longitudinal stripes ( Fig. 9d View Figs ). This species is most similar to I. adunca   ( Figs. 4 View Figs a-h & 20b) in that it lacks abdominal stripes ( Fig. 9d View Figs ), but can be separated by the interrupted lacinia submarginal setae row ( Fig. 9g View Figs ).

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


Angelo State University


Toleco Museum of Health and Natural History














Isoperla laucki Baumann & Lee

Sandberg, John B. 2011

Isoperla laucki

Isoperla laucki Baumann & Lee 2009