Oecetis disjuncta (Banks)

Blahnik, Roger J. & Holzenthal, Ralph W., 2014, Review and redescription of species in the Oecetis avara group, with the description of 15 new species (Trichoptera, Leptoceridae), ZooKeys 376, pp. 1-83 : 28-30

Oecetis disjuncta (Banks) Figs 8, 31, 39, Map 2

Oecetina disjuncta Banks, 1920: 351 (pl. 7, fig. 100) [holotype male, California, Arroyo Seco Canyon, San Gabriel Mts., Switzer’s Camp, June 17, MCZ type 10915].

Oecetodes disjuncta (Banks): Milne 1934: 17, 19.

Oecetis disjuncta (Banks): Ross 1938: 24; Denning 1956: 265 [as possible synonym of Oecetis avara ]; Smith and Lehmkuhl 1980: 638 (Figs 1-2, 5, 7, 9-10, 12, 14, 16, 18, 21, 23, 25-26, 29-34, 37-38, 40-41, 43, 45, 46-48, 50) [adult, larva, pupa, case, distribution - Figs are of Oecetis sordida sp. n. and not Oecetis disjuncta ]; Floyd 1995: 29 (fig. 22A-H, map 25) [larva, case, distribution - figure and all, or most, records undoubtedly of Oecetis sordida , and not Oecetis disjuncta ].

Diagnosis.

This species differs from the form that has most often been attributed to it, here described as a new species, Oecetis sordida . The 2 are very similar and it is not surprising that Smith and Lehmkuhl (1980) came to the conclusion that the specimens they had examined from Saskatchewan represented this species after examining the holotype. They did note, however, the variation in the length of the preanal appendages, one useful diagnostic character for distinguishing the species. We have examined only a few specimens from California and Oregon that correspond to the holotype of Oecetis disjuncta , probably primarily due to the paucity of material from this region in the collections surveyed. Nevertheless, the character differences from Oecetis sordida seem to be consistent. It is true that the genitalia in these 2 forms are very similar, with the dorsal and ventral lobes of the inferior appendage merely “notched”, rather than with the ventral lobe distinctly projecting, and with the ventral margin of the phallobase strongly deflexed, and also with an asymmetrical phallic sclerite absent. However, the holotype of Oecetis disjuncta , which was described from California, is much lighter in color (a uniform pale yellowish-brown) than any specimens of Oecetis sordida (dark brown with a distinctly pigmented chord), is somewhat smaller in size, and has the preanal appendages distinctly more elongate. Additionally, Oecetis disjuncta lacks the distinctive rugose ventral apex of the phallobase that seems to consistently occur in Oecetis sordida . Oecetis sordida is nearly invariant in coloration and morphology throughout its very extensive range (southern Mexico and throughout the western United States, apparently as far east as Michigan). Despite the very limited material examined for Oecetis disjuncta , its separate species status is suggested by the distinct COI barcode difference of a specimen from Oregon identified as Oecetis disjuncta , as compared to Oecetis sordida and Oecetis avara (Fig. 58). Our decision to restrict the definition of Oecetis disjuncta to only those forms exactly resembling the holotype was made to stabilize the nomenclature of the taxon and to prevent its confusion with the form described here as Oecetis sordida . It should be pointed out that Oecetis disjuncta also closely resembles Oecetis apache sp. n., in the general structure of the genitalia, coloration, and lack of forewing pigmentation. The latter species differs in having the apex of phallobase distinctly V-shaped in caudal view (i.e., its ventral apex is strongly “keeled,” rather than U-shaped), and is also larger and has slightly broader forewings.

Adult.

Forewing length: male (9.7-10.2 mm). Color (holotype and California specimen) yellowish-brown, (Oregon specimens) light brown. Antennae whitish with indistinct, narrow annulations at intersection of antennomeres. Forewing spots absent or nearly so; chord nearly unpigmented in holotype, lightly pigmented in specimens from Oregon. Forewing chord with crossveins moderately spaced, diagonal or perpendicular, either nearly evenly spaced or with s and r-m veins slightly closer. Forewings moderately setose, nearly uniformly along length, setae along veins in apical part of forewing not denser than on wing membrane, not conspicuously laterally diverging. Fringe of setae along costal margin of forewing dense, short, not strongly projecting.

Male genitalia.

Segment IX very short, with elongate setae along posterolateral margin. Tergum X with narrow, deflexed mesal lobe, lobe short, tapering apically, apex with small sensilla; lobe continuous basoventrally with paired lateral membranous projections. Preanal appendage elongate, length about 5 times maximum width, simple in structure, apical setae elongate. Inferior appendage with prominent rounded dorsal lobe and scarcely projecting ventral lobe, separated from dorsal lobe by shallow, rounded notch; posterior margin of ventral lobe, as viewed ventrally (Fig. 8E), with rounded bend near base, lobes very weakly diverging; basomesal projection of appendage forming weakly to moderately developed projection with short, stiff setae; dorsal lobe with stout, mesally-curved setae on dorsal margin and ventrally-curved setae on mesal surface (entire surface nearly denuded in holotype). Phallobase relatively short, ventral apex strongly, angularly deflexed, bend close to apex, apex distinctly sclerotized, but not rugose; ventral apex, as viewed caudally, U-shaped (Fig. 8C). Phallotremal sclerite prominent, basally forming relatively large tubular collar, ventral margin projecting; asymmetrical lateral sclerite absent.

Material examined.

USA: California: Arroyo Seco Canon, San Gabriel Mts. Switzer’s camp, 17.vi--, male (holotype 10915) (MCZ); Turner, East Lake (locality not found), Rec. 21.vi.1883, 1 male (pinned) (NMNH); Oregon: Douglas Co., Umpqua National Forest, Steamboat Creek @ Forest Road 38, 5.4 mi NE Hwy 138, 43°22.583'N, 122°39.203'W, 485 m, 15.viii.2006, Holzenthal et al., 2 males (UMSP).