trilineatus Fox, 1946: 250 (female). Type locality: Virgin Islands, St. Thomas, Red Hook. HT F
(UNPR). Distr.- Guatemala to Panama, Puerto Rico, Virgin Islands, Dominica, Barbados, Guadeloupe, Paraguay, Argentina (Salta: San Ramón de La Nueva Orán, 23°8'29.16''S, 64°18′31.03″W; Cornejo, 24°48'21.85"S, 65°25'24.12"W. Formosa: Estanislao del Campo, 25°3'12.50"S, 60°5'38.10"W; Chaco: La Chiquita, 26°50'32.14"S, 60°20'4.07"W; Sáenz Peña, 26°48'1.59"S, 60°25'52.45"W; Zapirain(?); Misiones: Iguazú, 25°35'49.79"S, 54°34'42.96"W; Panambí, 27°43'26.66"S, 54°54'54.36"W; Bernardo de Irigoyen, 26°14'59.57"S, 53°59'1.56"W; Aristóbulo Del Valle, 27°5'16.30"S, 54°57'8.64"W). Refs.: Forattini, 1957: 389; Cavalieri & Chiossone, 1966: 149; Díaz et al., 2018a: 878.



The fourth instar larva and pupa of Culicoides trilineatus Fox, a species considered as potential vector of the bluetongue virus (BTV) in Central and South America, are described, illustrated, and photomicrographed for the first time by using binocular, phase-contrast, and scanning electron microscopy. The immatures were collected by using a siphon bottle in tree-holes in Salta Province, Argentina, transported to the laboratory and there reared to the adult's emergence. They are compared with the immatures of C. debilipalpis Lutz, another Neotropical species that develops in tree holes. Details on larval biology and habitat are given