Holotype: ♂ (Fig. 2). [printed on white paper] COLOMBIA: Valle del Cauca/Cali, Pance, Loma Larga/1200m, 3°19'N/76°34'W/1 April 2011/Leg. M.D. Heredia. [printed label on red paper] Holotype/Thereus lomalarga/Robbins, Busby, & Heredia. [printed white barcode label] Instituto Humboldt/Colombia/IAvH-E-146988. Deposited IAVH.

Paratypes (32♂, 41♀). Costa Rica. 1♀ Turrialba, 2,000 ft, 13 Jul 1965 (USNM). Panama. Canal Area. Paraíso, Cerro Luisa, 4 Feb 1979 (2♂ USNM), 16 Feb 1979 (1♂ USNM), 1 Mar 1979 (1♂ USNM), 4 Mar 1979 (1♂ USNM), 10 Mar 1979 (1♂ USNM). Pedro Miguel, Chiva Chiva Road, 14 Jan 1979 (1♀ USNM). Panama Province. Cerro Campana. 1500 ft/500m. 3 Jan 1965 (1♀), 26 Jan 1966 (1♀ USNM), 28 Jan 1980 (1♀ USNM). 850 m. 23 Feb 1979 (1♀ USNM). Chiriquí Province. Potrerillos. 3600 ft. 27 Dec 1965 (1♀USNM), 28 Dec 1965 (2♀ USNM), 27 Dec 1965 (1♀USNM), 1 Jan 1966 (2♀ USNM), 28 Jan 1966 (2♀ USNM), 29 Jan 1966 (1♀ USNM), 2 Feb 1966 (1♀ USNM), 19 Feb 1966 (1♀ USNM), 5 Mar 1966 (1♀ USNM). Colombia. Valle del Cauca, Cali. Pance, 3000 ft, 14 Jan 1985 (1♀ USNM)). Loma Larga, 1200m. 3°19'N/76°34'W. 15 May 2009 (1♂ MUSENUV).18 Nov 2010 (1♂ USNM, IAvH-E-112219). 5 Dec 2010 (1♂ MUSENUV). 10 Dec 2010 (1♀ MUSENUV). 13 Jan 2011 (1♀ USNM, IAvH-E-112207). 15 Mar 2011 (1♀ MUSENUV). 17 Mar 2011 (1♀ MUSENUV). 19 Mar 2011 (1♀ MUSENUV). 31 Mar 2011 (1♀ MUSENUV). 1 Apr 2011 (1♂&1♀ MUSENUV). 2 Apr 2011 (1♂ MUSENUV). 5 Apr 2011 (1♀ MUSENUV). 6 Apr 2011 (1♀ IAVH, IAvH-E-146990). 24 Apr 2011 (1♂ IAVH, IAvH-E-146982). 21 May 2011 (1♂ USNM, IAvH-E-146983). 29 May 2011 (1♂ MUSENUV). 30 May 2011 (1♂ IAVH, IAvH-E-146987). 1 Jun 2011 (1♂ USNM, IAvH-E-146985). 15 Jun 2011 (1♂ MUSENUV). 17 Jun 2011 (1♂ MUSENUV). 21 Jun 2011 (1♀ IAVH, IAvH-E-146986). 23 Jun 2011 (1♂ MUSENUV). 27 Jun 2011 (1♀ MUSENUV). 28 Jun 2011 (1♀ IAVH, IAvH-E-146984). 14 Jul 11 (1♂ MUSENUV). 23 Jul 2011 (1♂ MUSENUV). 17 Dec 2011 (1♀ MUSENUV). 31 Dec 2011 (1♀ USNM, IAvH-E-146989). 20 Feb 2012 (1♂ MUSENUV). 23 Feb 2012 (1♀ MUSENUV). 3 Mar 2012 (1♂ MUSENUV). 4 Mar 2012 (1♂ MUSENUV). 6 Mar 2012 (1♂ MUSENUV). 12 Mar 2012 (1♂ MUSENUV). 3 Apr 2012 (1♂ MUSENUV). 15 Apr 2012 (1♂ MUSENUV). 19 Apr 2012 (1♂ MUSENUV). 22 Apr 2012 (1♀ MUSENUV). 29 Aug 2012 (1♂ MUSENUV). 25 Jun 2014 (1♀ MUSENUV). 4 Jul 2014 (1♂ MUSENUV). 3 Jul 2014 (1♂ MUSENUV). Ecuador. Pichincha, 10 km Celica-Sardinas Road, 0°11.6'N, 79°00.8'W, 550-775 m, 27 May 2008, (1♀ RCB); 7 km Pacto-Guayabillas Road, 0°09.0'N, 78°48.9'W, 1600m, 18 Jun 2014, (2♀ RCB); 5 km Nanegal- García Moreno Road, 0°09.2'N, 78°39.4'W, 1375–1700m 21 Jan 2015, (1♀ RCB); 24 May 2008, (1♀ RCB).

This species is named for Loma Larga, a housing development on the outskirts of Parque Nacional Natural Farallones de Cali. Loma Larga has had an ecological and conservation policy for about 15 years that has designated a substantial plot of land for natural forest regeneration (Fig. 27) in contrast to cow pasture. The name is a noun in apposition.

(Fig. 27). The type locality is naturally regenerated forest in Loma Larga.

Thereus lomalarga belongs to Thereus because it possesses the synapomorphies of the genus (Figs 16, 23, 25). It belongs to the Thereus oppia species group (Figs 2, 10, 13). It shares a dorsal forewing scent pad with Thereus brocki (Figs 6, 8), but differs in having an iridescent scent patch on the dorsal hindwing and in lacking erect piliform setae on the inner margin of the ventral forewing (Figs 2, 10, 13). The male has evident teeth on the dorsal tip of the penis (Fig. 16), which distinguishes it from Thereus orasus and Thereus brocki. The wing pattern, androconia, genitalia, and antennae are illustrated (Figs 2, 6, 10, 13, 16, 20, 23, 25). Mean forewing size of males is 11.67 mm (sd = 0.52, N = 23) and of females is 11.34 mm (sd = 0.65, N = 16).

Expression of the female orange-red spot at the anal lobe of the ventral hindwing between vein Cu₂ and the inner margin varies from a fused double spot, as in Fig. 2, to completely absent. The ventral ground color varies from gray to brown. The postmedian line on the ventral hindwing varies slightly in shape from that in Fig. 2 to that of Thereus brocki in Fig. 4.

(Fig. 26). Costa Rica to the western slope of the Andes in Ecuador. It is allopatric with Thereus orasus, its hypothesized phylogenetic sister (Fig. 28). Their ranges overlap in Costa Rica and Panama, but in these countries, Thereus lomalarga is recorded below 1100 m and Thereus orasus at 1800 m.

Thereus lomalarga occurs in the great variety of forested habitats. In Central America, it occurs from sea level to lower montane humid forest at 1100 m elevation. In South America, it also occurs at elevations up to 1600 m. Although two females have labels with the elevation range 1375–1700 m, we have since learned from the collectors that they were found in the lower half of this range.

Adults in Panama were collected during the dry season without exception, suggesting adult seasonality. However, caterpillars in Colombia were found throughout the year and reared to the adult stage. Perhaps adults of this species are more apparent to collectors during the dry season.

Six males displayed territorial hilltopping behavior from 09:00–09:30 hours during the dry season (February, March 1979) at the top of a small tree on the southwest edge of the summit of Cerro Luisa, Paraíso (9°02'N, 79°37'W), Canal Area, Panama (vouchers in USNM). The longitude on one specimen is incorrectly labeled 79°38'W.

Oryctanthus alveolatus (H.B.K.) Kuijt (Loranthaceae) growing on Miconia minutiflora (Bonpl.) DC. Details of the life history will be published elsewhere (Heredia and Robbins in prep.).

Thereus lomalarga is a peculiar butterfly in that adult females are far more frequently encountered—at least by butterfly collectors—than are adult males. For example, all collected adults from Costa Rica, Colombia, and Ecuador are females. Among collected adults in Panama, females have been found from sea level in the Canal Area to Cerro Campana (at about 850 m along the trail to the summit, Panama Province) to Potrerillos at 1,100 m (Chiriquí Province). In contrast, adult males have been collected only at the top of one small tree on Cerro Luisa in the Canal Area in the dry season in 1979. All other males, including the holotype, were reared from caterpillars. Among 44 reared individuals at the type locality, 27 are males, so the sex ratio among immatures is not biased towards females.

No museum specimens other than those in the type series have been seen by the authors. However, females of Thereus lomalarga are “non-descript small gray hairstreaks”, and other specimens may be found in museum collections.