Isoperla laucki, Baumann & Lee, 2009

Baumann, Richard W. & Lee, Jonathan J., 2009, Two Interesting New Species Of Isoperla From Northern California (Plecoptera: Perlodidae), Illiesia 5 (1), pp. 1-10 : 2-5

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Isoperla laucki


Isoperla laucki   sp.n.

( Figs. 1‐16 View Figs View Figs , 33 View Figure )

Material examined. Holotype ♂ from California, Humboldt Co., Dragsaw Spring @ Rd 13N01 , 23‐VIII‐ 07, J.J. Lee   . Paratypes (J.J. Lee, Collector): – California, Humboldt Co., Red Mountain Ck. @ Rd 10 N12, 4‐VIII‐05, 1 ♀   ; 10‐VIII‐05, 1 ♀; 20‐X‐05, 1 ♀; 14‐XII‐05, 9 larvae; 23‐VI‐06, 3 ♀; 3‐VII‐06, 2 ♀; 25‐ VIII‐06, 6 ♂, 1 ♀, 4 larvae; 25‐VII‐07, 1 ♀, 2 larvae, 1 ♂ (reared 9‐VIII‐07); 8‐VIII‐07, 1 ♂, 1 larva; 23‐VIII‐07, 1 ♀, 1 ♂ & 1 ♀ (reared 26‐VIII‐07), 1♂ (reared 27‐VIII‐ 07)   , 1 ♀ (reared 28‐VIII‐07); 29‐VIII‐07, 1 larva; 11‐ VIII‐08, 3 larvae, 1 ♀ (reared 29‐VIII‐08); Dragsaw Spring @ Rd 13 N01, 25 ‐VII‐07, 1 ♂, 1 ♀; 29‐VIII‐07, 1 ♀; 11‐VIII‐08, 1 ♀; 28‐VIII‐08, 1 ♂; spring east of Boise Ck. , Hwy. 299, 21‐III‐07, 1 larva   ; spring @ East Fork Willow Creek Campground , 3‐VII‐07, 1 ♂   ; 10‐VII‐07, 1 ♂, 1 ♀; 28‐V‐08, 1 ♀; 9‐VI‐08, 2 larvae. Holotype deposited at the California Academy of Sciences   .

Male. Macropterous. Length of forewings 10.0‐11.0 mm; length of body 9.0‐10.0 mm. General body color golden yellow. Head yellow, light U‐ shaped pattern forward of anterior ocellus, orange brown patch inside “U” extends to frontal margin; interocellar area light orange brown; occiput orange brown mesally behind lateral ocelli, occipital suture lines light; posterior corners behind eyes with brown rugose patch and scattered short spinules. Antennae yellow at base, infuscate distally. Pronotum widest anteriorly, with narrow band of light brown rugosities lateral to median, yellow stripe. Wings slightly hyaline yellow, veins brown, and fumose yellow in costal space. Legs yellow, covered with short spines, tibiae with incomplete dorsal brown band in proximal one‐ fourth. Abdomen bright yellow, vesicle on eighth sternum yellow orange, with scattered short setae, longer setae on posterolateral margins, shallowly rounded posteriorly and appearing oval, width approximately 1.5 to 2 times length. Tenth tergum with posteromedian depression and anteromedian unsclerotized area. Cerci golden brown with scattered short setae, one or two ventral setae approaching 1/2 segment length distally on each segment. Paraprocts bluntly pointed, curving slightly over tergum 10 ( Fig. 9 View Figs ). Aedeagus ( Figs. 1, 3‐4 View Figs ) with an elliptical‐ shaped patch of stout, brown spinules, located dorsally, patch ranging from 2 to 3 times as long as wide ( Figs. 2 & 5 View Figs ); posterobasal patch of short stout, orange brown spinules, forming sinuate rows ( Fig. 6 View Figs ); a stronger patch of posteromedial orange brown spinules ( Fig. 7 View Figs ) becoming smaller and scattered laterally; aedeagus narrowing apically, cleft at apex, with a short, digitate, lightly sclerotized process arising from cleft ( Figs. 4 & 8 View Figs ).

Female. Macropterous. Length of forewings 11.5‐12.5 mm; length of body 10.0‐11.0 mm. General body color, head and pronotal pigmentation patterns similar to male. Subgenital plate broadly triangular but rounded apically, extending at least over one‐ half length of ninth sternum ( Fig. 10 View Figs ).

Egg. Shape nearly triangular in cross section, short and angular, with five nearly equal sides ( Figs. 15‐ 16 View Figs ). Collar poorly developed and appearing as a flattened cap. Chorion with thick ridges interspersed with deep angular depressions that cover the remainder of the outer surface. Micropyles set on ridges near bottom third of egg. Mature eggs light brown and almost translucent, appearing like small jewels in preserved specimens.

Larva. Body length of mature nymph 9.0‐10.0 mm. General body color brown, with dark clothing hairs. Dorsum of head brown, light M‐ shaped pattern forward of median ocellus, frontal margin pale, small oval, light patch between frontal pale band and peaks of “M” pattern, similar light patch between median ocellus and compound eyes; interocellar area brown, occiput with light, oval patch adjacent to eyes; light patch posteriorly on occiput broken by dark reticulate lines; sinuate band of occipital spinules separating the two light patches; posterior corners behind compound eyes brown with scattered spinules ( Fig. 33 View Figure ). Antennae light brown with apical circlets of short setae; dark clothing hairs on basal segments. Lacinia triangular, bidentate; subapical tooth ca. 1/2 length of apical tooth; 1 or 2 axillary setae, 6‐8 stout marginal setae below subapical tooth, setae 7 and/or 8 small; 2 fine submarginal setae below subapical tooth; sparse, irregularly spaced fine marginal and submarginal setae below stout marginal setae ( Figs. 13‐14 View Figs ). Mandibles with 6 cusps in 2 groups of 3; at least middle cusp in each group serrate; median row of long medium stout setae below outer apical cusp to near mandibular base; inner marginal fringe of 40+ long stout setae; right mandible with row of short stout setae below inner 3rd apical cusp ( Fig. 11 View Figs ), setae longer and row more extensive on left mandible. Pronotum oval, width slightly narrower than head, brown with reticulate light markings and dark brown border, slightly lighter brown laterally; margin fringed with small stout setae, occasionally longer setae at upper and lower angles and lateral margin. Meso and metanota brown with reticulate markings. Legs light brown with scattered variable sized stout setae, with sparse dorsal fringe of silky setae ( Fig. 33 View Figure ). Thoracic sterna with distinct mesal sclera with dark clothing hairs; mesosternal Y‐ ridge arms extend to posterior corners of furcal pits; with band of erect bristles scattered across anterior surface of mesosternum. Abdominal segments dark brown; terga with paired mesal and lateral light spots; sometimes a third light spot evident forming a mesal triangle with anteromedial pair; lateral light spots often obscured posterior to first few tergites. Cerci with ca. 28 segments; each with posterior circlet of setae, lacking setal fringe.

View Figure View Figure

Etymology. We are proud to name this species in honor of our friend, teacher, and colleague David R. Lauck, who taught for many years at Humboldt State University in Arcata, California. He instilled in us the excitement and desire to study the stonefly fauna of the Willow Creek area and the greater TrinityKlamath River drainage. Humboldt Stripetail is suggested as the common name.

Diagnosis. This species is unique among described western Isoperla   . Adults in the field can be recognized by the golden yellow color, superficially resembling robust Sweltsa   . Males can be distinguished by the oval patch of strong spinules dorsally on the aedeagus and the unique lightly sclerotized digitate apical process ( Figs. 1‐4 View Figs ). Nymphs can be distinguished from other western Isoperla species   by the presence of an M‐ shaped pattern on the head, the lack of abdominal striping ( Fig. 33 View Figure ), and the erect bristles anteriorly on the mesosternum. Erect bristles are evident in early instars but may be worn off in mature later instars. Nymphs superficially resemble small Chernokrilus misnomus (Claassen)   and Calliperla luctuosa (Banks)   , however, the small size of late instars, combination of lack of abdominal striping and mesosternal “Y”‐arms meeting the posterior corners of the furcal pits, and erect mesosternal bristles distinguishes them. Females have a rounded subgenital plate that extends over half of sternum nine ( Fig. 10 View Figs ). The eggs have a distinctive angular shape, with five nearly equal sides ( Figs. 15‐16 View Figs ).

Remarks. This species was found in small, perennial spring creeks between 400 and 900 meters elevation. Summer water temperatures ranged from 8 ° C to 12 ° C, summer air temperature regularly exceeded 27 ° C. Females with mature eggs were found from June to October indicating an extended emergence. Early instar nymphs were collected in December; mid to late instar nymphs in March through August, suggesting a univoltine life cycle. Other Perlodidae   found with I. laucki   include: C. luctuosa   , C. misnomus   , and Salmoperla sylvanica Baumann & Lauck.  

“Drumming” behavior was observed in one male specimen. A laboratory reared female was placed in a container with a field caught male. After approximately 25 hours the female came out of hiding and mating occurred within 15 minutes. The male was observed to touch his vesicle to the substrate 3 to 5 times then raise his abdomen above horizontal and vibrate it before rapidly bringing it back down. This apparent “tremulation” has not been previously reported for Isoperla ( Stewart 2001)   and further investigation is warranted.