Simulium (Hearlea) microbranchium Dalmat

Figs. 1H–I, 4J–K

S. (Simulium) microbranchium Dalmat, 1949: 538–544, Figs. 1–9.

S. (Hearlea) microbranchium Dalmat, 1951: 50–52; 1955: 72, 76, 82, 87, 268–272; Figs. 112–114, 232–234, 257, 314, 354, 392, 429.

Female: Wing length, 3.4 mm. Front and clypeus brownish­gray silvery pollinose. Thorax brownish black. Scutum brownish dark, with silver submedian vittae not adjoining anterior 1+1 silvery subtrapezoidal spots, but adjoining silvery pollinose prescutellar area; area between these spots black, although changing light position changes this silver color to black (Figs. 1H–I). Scutum with golden, closely adpressed pilosity. Shape and proportion of palpus sensory vesicle as in S. capricorne . Cibarium with median portion concave, hyaline, with serrated margins. Sc haired. Length/width ratio of hind basitarsus = 5.2. Genitalia structurally similar to S. capricorne .

Male: Wing length, 3.4 mm. Scutum velvety black with whitish pruinosity anteriorly and bordered with narrow silvery band on periphery. Scutum pilosity golden. Sc haired. Genitalia typical for subgenus; ventral plate with small median crest. Dististylus length ca. 2X that of basistylus height at site of insertion; basistylus height at external margin 1/3 longer than at internal margin.

Pupa: Cocoon weakly shoe shaped, closed and slightly enlarged anterobasally, with reinforced margin (Fig. 4J). Length (basal), 3.5 mm. Base of frontoclypeus and anterodorsum of thorax with few platelets. Gill comprised of 2 laterally flattened, dorsally pseudosegmented, accuminate branches (Fig. 4K); dorsal branch (length = 1.6 mm) directed anteriorly, forming ca. 90° angle with gill base; ventral branch 0.9 mm, directed only slightly medially.

Larva: (Diagnosis derived from Dalmat, 1951). Body length, 7.7 mm. General coloration gray. Cephalic apotome concolorous, with small black spots along midline and submedian anterior area. Labral fan with 56 or 57 primary rays. Hypostoma with median tooth and corner teeth longer than other teeth. Postgenal cleft curved with narrow anteromedian incision. Lateral sclerite of thoracic proleg with 37–39 teeth. Posterior circlet with 194– 206 rows of hooks. Rectal papillae trilobed, with ca. 25 lobules per lobe (75 total). Anal sclerite simple, lacking scales.

Material examined: Guatemala: (Dalmat collection USNM) Totonicapán, Totonicapán río Samalá, 1 male allotype (in slide and its pupal exuvia), 8 pupal exuviae (paratypes), and 28 pupae, (mostly exuviae from material reared by Dalmat), 11 December 1947, Ochoa & Dalmat; El Quiché, Nebáj, río Micovez, 2 pupae, 10 December 1948; 2 males, 2 pupal exuviae, 15 November 1949; 10 females, 4 males, 6 pupal exuviae, 15 November 1950; 1 female, 28 March 1951; 6 females, 4 males, 6 pupal exuviae, 30 August 1951; 6 females, 10 males, 15 pupal exuviae, 30 September 1951; Huehuetenango, between Quetzaltenango and Huehuetenango, río Pajonal, 1 female, 3 pupae, 15 December 1948; Sololá, Panajachel, Catarata El Puente, 1 pupa, 16 March 1949; 1 female, 1 male, 1 December 1949; río Los Arcos near Los Encuentros, 1 pharate female, 1 pupal exuvia, 9 November 1948.

Distribution: Guatemala: Totonicapán, El Quiché, Sololá, Huehuetenango, Quetzaltenango.

Discussion: This species is very similar to S. ayrozai, which differs by its gill branches being largely or entirely concealed by the anterior margin of the cocoon.