Oecetis metlacensis Bueno-Soria

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 : 41-44

Oecetis metlacensis Bueno-Soria Figs 16, 17, 36, Map 5

Oecetis metlacensis Bueno-Soria 1981: 109, Figs 5, 6 [holotype male, Mexico, Veracruz, 5 km from Puente Villa Unión (IBUNAM)]; Houghton 2001: 91 [distribution - Arizona (specimens reassigned here to Oecetis apache sp. n.)].

Diagnosis.

Oecetis metlacensis is most readily diagnosed by its relatively large size (although this seems to be somewhat variable in specimens examined from Mexico), coloration (yellowish-brown with small forewing spots), shape of the inferior appendage, and by the V-shaped ventral apex of the phallobase, in caudal view. It is most similar to Oecetis uncata sp. n., Oecetis apache sp. n., and Oecetis angulata sp. n., all of which are in about the same size range and have the apex of the phallobase V-shaped in caudal view. Oecetis uncata has the ventral lobes of the inferior appendage more distinctly projecting and angled, and also has more distinct forewing spots, as well as a phallobase that is angled more apically. Oecetis apache differs in having the dorsal lobe of the inferior appendages more robust and the ventral lobe less defined, as well as in lacking any forewing spots at all. Its forewings are also somewhat wider. Oecetis angularis is lighter in color, has more distinct forewing spots, and has the phallobase less distinctly angled in lateral view. Oecetis metlacensis is also similar in size and general genitalic features to both Oecetis disjuncta and Oecetis sordida sp. n., but both of these species have the apex of the phallobase rounded or U-shaped, as viewed caudally.

Adult.

Forewing length: male (9.7-13.0 mm), female (6.9-10.0 mm). Color yellowish-brown. Antennae whitish with indistinct, narrow annulations at intersection of antennomeres. Forewing spots small, indistinct; spots at base of discal and thyridial cells and base of fork V largest, other spots very small; veins of forewing chord with m widely spaced, s and r-m veins relatively close; chord with very small spots at juncture of major veins; apical spots, at apices of major veins, not or scarcely evident. Forewings rather densely setose apically (causing apex to appear darker as viewed without magnification), setae along veins in apical part of forewing moderately elongate, semi-prostrate, 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, very short in specimens from Costa Rica, tapering apically, apex with small sensilla; lobe continuous basoventrally with paired lateral membranous projections. Preanal appendage moderately elongate, length about 3 times maximum width, simple in structure, apical setae elongate. Inferior appendage with prominent, short rounded dorsal lobe and weakly to moderately projecting ventral lobe, separated from dorsal lobe by broadly rounded emargination; basomesal projection of appendage forming distinct rounded projection with short, stiff setae; dorsal lobe with stout, mesally-curved setae on dorsal margin, anteroventrally directed setae on anterior margin, and ventrally-curved setae on mesal surface. Phallobase moderately elongate and tubular basally, strongly, subangularly deflexed, more angularly in specimens from Costa Rica; ventral apex, as viewed caudally, V-shaped (distinctly keeled). Phallotremal sclerite prominent, basally forming relatively large tubular collar, ventral margin somewhat projecting, apex acute; asymmetrical lateral sclerite absent.

Material examined.

MEXICO: Veracruz: Río Tacolapan, Rt. 180, Km 551, 25-26.vii.1966, Flint & Ortiz, 2 males, 1 female (Paratypes, pinned), 1 male, 15 females (alcohol) (NMNH); Puente Tacolapan, E Tehada, 4.xii.1975, C.M. & O.S. Flint, Jr., 1 male (Paratype, pinned) (NMNH); Río Jamapa, 6 km N Coscomatepec, 2.v.1981, C.M. & O.S. Flint, Jr., 1 male (pinned) (NMNH); COSTA RICA: Puntarenas: Río Bellavista, ca. 1.5 km NW Las Alturas, 8°57.060'N, 82°50.760'W, el 1400 m, 18.ii.1986, Holzenthal, Morse, Fasth, 2 males, 3 females (alcohol) (UMSP); same location, 15-17.vi.1986, Holzenthal, Heyn, Armitage, 6 males (alcohol) (UMSP); same location, 8-9.iv.1987, Holzenthal, Hamilton, Heyn, 13 males, 11 females (alcohol) (UMSP); same location, 2-3.viii.1987, Holzenthal, Morse, Clausen, 7 males, 6 females (alcohol) (UMSP); same location, 10-11.viii.1990, Holzenthal, Blahnik, Muñoz, 16 males, 13 females (alcohol) (UMSP); same location, 16-17.iii.1991, Holzenthal, Muñoz, Huisman, 33 males, 24 females (alcohol) (UMSP); same location, 23.ix.1991, F. Muñoz & F. Quesada, 3 males (pinned) (UMSP); trib to Río Bellavista in Las Alturas (road to quarry), 8°57.120'N, 82°50.880'W, el 1480 m, 13-14,viii.1990, Holzenthal, Blahnik, Muñoz, 3 males (alcohol) (UMSP); Río Cotón in Las Alturas, 8°56.280'N, 82°49.560'W, el 1360 m, 18.ii.1991, Holzenthal, Muñoz, Huisman, 7 males, 6 females (alcohol) (UMSP); same location, 12.viii.1990, Holzenthal, Blahnik, Muñoz, 4 males, 5 females (alcohol) (UMSP); Zona Protectora Las Tablas, Río Cotón, Sitio Cotón, 8°56.460'N, 82°47.220'W, el 1460 m, 15.iv.1989, Holzenthal & Blahnik, 2 males, 6 females (alcohol) (UMSP); Río Guineal, ca 1 km (air) E Finca Helechales, 9°4.560'N, 83°5.520'W, el 840 m, 4.viii.1987, Holzenthal, Morse, Clausen, 29 males, 17 females (alcohol) (UMSP); Río Singri, ca. 2 km (air) S Finca Helechales, 9°3.420'N, 83°4.920'W, el 720 m, 21.ii.1986, Holzenthal, Morse, Fasth, 24 males, 30 females (alcohol) (UMSP). San José: Río Chirripó Pacífico, 9.5 km NE Rivas, 9°28.200'N, 83°35.460'W, el 1370 m, 23.ii.1986, Holzenthal, Morse, Fasth, 4 males, 2 females (alcohol) (UMSP).

Remarks.

Specimens of Oecetis metlacensis from Costa Rica are slightly different from those in Mexico. They agree in size and general color with the largest specimen examined from Mexico ( Río Jamapa, Veracruz - Fig. 36). Paratype specimens examined from Mexico were distinctly smaller (but similar in coloration), accounting for the large size variance in the description of the species. Material examined from Mexico was limited, and thus it is difficult to assess the significance of the size variation observed in Mexican specimens. Compared to the paratype specimens from Mexico, the Costa Rican specimens have the apex of the phallobase slightly more elongate (Fig. 17B), the ventral lobe of the inferior appendage slightly more produced (Fig. 17A), the basomesal process of the inferior appendage more distinctly rounded (Figs 17A, 17D), and the mesal process of tergum X shorter (Fig. 17A). Mexican specimens were variable for most of these characters, especially in the development and angulation of the phallobase, without much evidence that this was anything more than intraspecific variation. A close side-by-side comparison reveals that specimens from Mexico and Costa Rica are very similar, especially when the variation among Mexican specimens is taken into account. In the absence of specimens from the intervening area between Mexico and Costa Rica and evidence to the contrary, this variation is here considered intraspecific.