(Hearlea) Vargas, Martínez Palacios & Díaz Nájera, 1946. Type species: Simulium canadense Hearle.
Female: Wing length, 2.5–5.0 mm. General coloration blackish brown; scutum blackish with 1+1 silvery vittae joining (Figs. 1F, G) or not (Figs. 1H, I) to 1+1 anterior submedian, subtriangular or subquadrate spots, and bordered laterally and posteriorly by silver pruinose areas. Legs yellowish to grayish brown, with apices dark brownblack. Frons convergent below (Fig. 1A), frontoocular triangle deep, about as long as wide (Fig. 1B); maxillary palpus with sensory vesicle elongate, nearly 1/2 length of basal article (Fig. 2B). Cibarium broadly Ushaped, with basal portion often thickened, medially cleft, and without strong teeth, although often with wrinkles or small serrations situated upon pair of sublateral, subovoidal prominences (Figs. 2A, F, G). Basal sector of R bare. Sc with 6–18 setae ventrally. Hind basitarsus 5.7–6.0 times longer than broad (Fig. 1C); claw with small, subbasal tooth (Figs. 1D, E). Gonapophysis subtriangular, with blunt apex, gradually concave internal margins, surpassing posterior margin of sternite VIII (Fig. 2C). Anal lobe subquadrate to subrectagular, sparsely haired, except for truncate distal margin (Fig. 2D). Genital fork with stout, capitate rod and apically expanded tines bearing strong anteriorly directed apodemes (Figs. 5E, H). Spermatheca ovoid, with internal spicules (Fig. 2I).
Male: Wing length, 2.6–5.0 mm. General coloration similar to female, differing as follows: Scutum generally velvety black with anterior 1/3 having whitish pruinosity (Fig. 3A). Sc typically bare. Hind basitarsus (Fig. 3B) 2.7–3.6 times longer than broad. Basistylus subquadrate, with small protuberance on external margin. Dististylus thin, elongate, 1/ 3 longer than basistylus, with small haired subbasal carina posteriorly, and one subapical spine (Figs. 3C, F). Ventral plate subquadrate, with narrow median carina (Figs. 3D, G). Endoparameres with broad base and numerous strong hooks (Fig. 3E). Median sclerite subrectangular.
Pupa: Cocoon slipper or shoe shaped, typically neatly and coarsely woven and with or without reinforced anterior margin; length at base ca. 3.5–4.5 mm (range = 2.4–7.0 mm) (Figs. 4–5). Gill inflated, gradually flattened, pseudosegmented (annulated), and lacking secondary branches (Figs. 4–5) to cylindrical, smooth, with having secondary branches (Fig. 6). Frontoclypeus gradually swollen basally (Figs. 3H, I). Frontoclypeus and anterodorsum of thorax smooth or covered with abundant impressed (concave) platelets or rounded or pointed (elevated) granules. Frontoclypeus with 2+2 frontal and 1+1 facial setae. Thorax with 3(4)+3(4) dorsocentral and 2+2 dorsolateral stout trichomes. Abdominal chaetotaxy as in Figure 7. Setae of abdominal tergite I relatively short, hairlike, with small platelets along anterior margin; setae of abdominal tergites II–VI short, slender. Tergites II–IV with 4+4 retrorse hooks, those of tergite II smaller; tergites V–VIII with minute spine combs. Tergite X with or without pair of terminal spines. Sternites IV–VII with small, wrinkled areas.
Larva: Body length, 6.5–12.0 mm. Posterior portion of body typically dorsally flattened and gradually distended ventrally (Fig. 9G); body without evident setae. Cervical sclerites free or adjoining posterior margin of postgena (Fig. 8D). Antenna longer than labral fan stalk, with proximal article elongate and deeply incised, creating segmented appearance; medial article longer than basal and distal (Figs. 8E, K). Cephalic apotome faintly darkened basally, typically lacking discernible headspots (Fig. 9D). Labral fan with 39–54 primary rays. Mandible with strong lateral process, robust intermedial and internal teeth, and two narrow marginal teeth (Figs. 8C–G). Postgenal cleft somewhat blunt to deeply incised apically (Figs. 8A, H, I); hypostomal bridge generally shorter than hypostomal height, ratio of hypostoma:hypostomal bridge = 0.7–1.5:1.0; anterior margin of hypostoma straight or curved (Figs. 8B, J), with median tooth longer than corner teeth. Anal sclerite sometimes encircling posterior circlet. Posterior portion of abdomen often with accessory plates (Figs. 9D, I, J). Rectal papillae of three major lobes, each with 15–78 secondary lobules. Posterior circlet with 102–400 rows of 16–27 hooks.
Bionomics: Immature stages are typically found on stones or vegetation in torrenticolous streams between 10–21°C in temperature at altitudes between 1000–3000m. Feeding habits of females are unknown.