Holotype: Male. GUATEMALA: Huehuetenango, La Democracia, Aldea Chamuxu, coordinates: 15.6333/-91.8667, 2 May 2016, C. Monroy and A. Rodas, National Museum of Natural History, Smithsonian Institution (voucher: USNMENT01241940). Paratypes: One female. GUATEMALA: Huehuetenango, San Pedro Necta, Caserio San Juan, coordinates 15.5/-91.76667, 1 June 2016, C. Monroy and A. Rodas, National Museum of Natural History, Smithsonian Institution, (voucher: USNMENT01241941). Two males. GUATEMALA: Huehuetenango, La Democracia, Aldea Chamuxu, coordinates: 15.6333/-91.8667, 2 May 2016, C. Monroy and A. Rodas, and GUATEMALA: Huehuetenango, San Antonio Huista, Canton Reforma, coordinates: 15.65/-91.7667, May 2016, C. Monroy and A. Rodas, Applied Entomology and Parasitology Laboratory- LENAP (ID: A10723 and A10685, respectively). Two females. GUATEMALA: Huehuetenango, La Democracia, Aldea Chamuxu, coordinates: 15.6333/-91.8667, 28 May 2016, C. Monroy and A. Rodas, and GUATEMALA: Huehuetenango, La Democracia, Aldea Chamuxu, coordinates: 15.6333/-91.8667, 28 May 2016, C. Monroy and A. Rodas, Applied Entomology and Parasitology Laboratory- LENAP (ID: A10800 and A10673, respectively).

The name Triatoma huehuetenanguensis is in reference to the locality (Department of Huehuetenango, Guatemala) where the holotype and paratype specimens were collected.

Specimens of T. huehuetenanguensis are classified as T. dimidiata following the key published by Lent and Wygodzinsky (1979). On closer examination, T. huehuetenanguensis differs from T. dimidiata in the following diagnostic characters: overall color of connexivum, color of head pilosity, ocelli, setae in the second antennomere, anterolateral angles, labial articles joints, setae in the abdomen, spiracles, and female and male terminalia.

In contrast to the connexivum and corium color of T. dimidiata (pale yellow to orange yellow), T. huehuetenanguensis is brown, with connexivum and corium from yellow to pale yellow. The ventral color in T. huehuetenanguensis is light yellow, while in T. dimidiata it is piceous or black (Fig. 2). The setae around the abdomen are less dense in T. huehuetenanguensis when compared to T. dimidiata. In T. huehuetenanguensis, the spiracles are adjacent to the connexival suture, while in T. dimidiata, the spiracles are close but not adjacent to the connexival suture. In addition, spiracles are surrounded by a dark spot in T. dimidiata, while the spot is absent in T. huehuetenanguensis (Fig. 5). The first antennomere in T. huehuetenanguensis does not reach the apex of the head, whereas in T. dimidiata, it does. The setae in the second antennomere of T. huehuetenanguensis are not as dense as in T. dimidiata (Fig. 3). Anterolateral angles are laterally oriented in T. huehuetenanguensis, while in T. dimidiata they are anterolaterally oriented. The three labial articles of T. huehuetenanguensis are light colored while in T. dimidiata they are dark, similar to the dark body color. The joint of each of the labial articles are pale yellow only in T. huehuetenanguensis (Fig. 3). The collar is relatively thicker in T. huehuetenanguensis compared with T. dimidiata. The scutellum is rugose in both, T. dimidiata and T. huehuetenanguensis. However, the central scutellum area in T. huehuetenanguensis is more depressed as compared with T. dimidiata (Fig. 4). Legs in T. huehuetenanguensis with 1 + 1 subapical denticles, sometimes with a very small apical denticle on fore and/or mid-femora. Females sometimes with only one subapical denticle or a callosity, slightly lighter than the tegument on its proximal side. Fore and mid-femora of both males and females with lighter ventral subapical band, ranging from almost imperceptible to yellow.

Figure 2. 

Comparison between T. dimidiata s. str. and T. huehuetenanguensis sp. n. A T. dimidiata female (left) and male (right) from Jutiapa (dorsal and ventral view) B T. dimidiata female (left) and male (right) from Huehuetenango (dorsal and ventral view) and C T. huehuetenanguensis sp. n. female (left) and male (right) from Huehuetenango (dorsal and ventral view). Photograph credits: RL and SJ.

Figure 3. 

Heads of T. dimidiata s. str. and T. huehuetenanguensis sp. n. Top panel, dorsal view of the head. Bottom panel, ventral view of the head. Abbreviations: o ocelli, ac apex of clypeus, ss stridulatory sulcus, r connections between rostral segments. Photograph credits RL and SJ.

Figure 4. 

Pronotum of T. dimidiata s. str. (left), and T. huehuetenanguensis sp. n. (right). Abbreviations: c collar, a anterolateral angles, h humerus and s scutellum. Photograph credits RL and SJ.

Figure 5. 

Ventral connexival plate and part of 4^th urosternite of T. dimidiata s. str. (left), and T. huehuetenanguensis sp. n. (right). Abbreviations: cs connexival suture and s spiracles. Photograph credits RL and SJ.

The terminalia in males of T. huehuetenanguensis is almost square-shaped and darker than the rest of the tegument, presenting sparse dark pilosity, while in T. dimidiata it is ovoid and dark, presenting abundant dark pilosity. Posterior margin of urosternite VIII convex on T. dimidiata and almost straight in T. huehuetenanguensis. Posterior margin of urosternite IX slightly sinuous and not exceeding the abdomen on T. huehuetenanguensis, convex and exceeding the abdomen on T. dimidiata. Female terminalia in both species is triangle-shaped with very dark and dense pilosity. However, in T. huehuetenanguensis it is pale and very pointed while, in T. dimidiata it has rounded apex and is dark colored. Posterior margin of sternite VII sinuous on T. dimidiata and very sinuous in T. huehuetenanguensis; gonocoxite VIII (Gc8) pointed on T. huehuetenanguensis and rounded on T. dimidiata; gonapophysis VIII (Gp8) is wider than long in T. huehuetenanguensis compared to T. dimidiata. Gonocoxite IX (Gc9) strongly expanded exceeding the abdomen in T. huehuetenanguensis compared to T. dimidiata (Fig. 6).

Figure 6. 

Comparison between the external terminalia of T. dimidiata s. str. and T. huehuetenanguensis sp. n. Abbreviations: Gc 8 gonocoxite VIII; Gc 9 gonocoxite IX; Gp8 gonapophysis VIII; VII sternite; IX and X segments. Drawings RL. Photograph credits RL and SJ.

Overall color brown, connexivum, and corium yellow to light yellow. Pilosity short, distinctively yellow, covering whole body, except male and female terminalia, where pilosity is brown.

Total length, male 22.5–26.5 mm, female 22.2–29.3 mm; pronotum width, male 4.9–6.2 mm, females 4.9–6.4 mm; pronotum length, male 3.7–4.2 mm, female 3.4–4.5 mm (Table 3).

Head dark brown with scarce yellow pilosity and overall smooth surface; central band with very shallow rugosity. Head length, male 4.1–4.7 mm, female 4.0–4.8 mm. Ocelli large, lighter than tegument, placed on a pronounced tubercle. Antenniferous tubercles subcylindrical, very short, situated in the middle of the anteocular region; first antennomere not attaining apex of head. Second antennomere lighter than first, with long setae. Ratio of antennomeres I–IV 1:3.9-4.4:3-4:2.5. Apex of clypeus distinctively lighter than rest of head. Labium (Fig. 3) slender, first article reaching level of apex of antenniferous tubercle; second article exceeding posterior border of head, attaining neck; third article light brown, with interarticular areas light yellow (Fig. 3). Ratio of labial articles 1: 1.6:0.5. Most labial setae short, not very numerous on first and second article. Third labial article reaching first third of stridulatory sulcus on males, half on females. Neck dark brown, with very smooth surface, and a pair of lateral yellowish spots.

Pronotum brown, with humerus blunt and pointed, usually lighter in color. Anterolateral angles short, almost round, laterally oriented, almost perpendicular to neck. Submedian carinae very pronounced, with tubercle aspect. Scutellum triangular, shallowly rugose, with the central area distinctly depressed, apical process sometimes lighter in color. (Fig. 4).

Hemelytra not reaching apex of the abdomen, darker at membrane, with scarce light yellow pilosity, dark brown spots around the intersection of the claval suture and the cubital vein, and two larger dark brown spots: one covering the posterior portion of the cubital and medial veins, and the other (largest) covering the joining of the radial and subcostal veins.

Abdomen ventrally convex, shortly pilose, yellow to light yellow (Fig. 3). Spiracles adjacent, but not touching connexival suture, not very pronounced, concolorous with rest of tegument. Connexival segments with a piceous or black spot covering the entire width of the anterior third, yellow posteriorly (Fig. 5).

Males terminalia almost square-shaped, darker than the rest of the body, with scarce dark pilosity. The posterior margin of urosternite VIII almost straight. Posterior margin of urosternite IX slightly sinuous and not exceeding the abdomen. Female external terminalia triangle-shaped, pale, with very dark, dense pilosity (Fig. 6). Posterior margin of sternite VII very sinuous; gonocoxite VIII (Gc8) pointed; gonapophysis VIII (Gp8) is wider than long. Gonocoxite IX (Gc9) strongly expanded exceeding the abdomen in T. huehuetenanguensis (Fig. 6).

Holotype and paratypes specimens of T. huehuetenanguensis were obtained by community participation and reported to be found in domestic environments, near to tropical forest. Huehuetenango is at the northwest of Guatemala and is characterized by pine forest. The altitude ranges from 300 to >3,000 m above sea level. Other localities (Table 1 and Fig. 1) were inferred from specimens collected for previously published molecular phylogenetics studies (Bargues et al. 2008, Dorn et al. 2016, Justi et al. 2018).

18 out of the 20 specimens tested were found to be infected with Trypanosoma cruzi.

The ecological diversity within the subfamily Triatominae (>150 species) and its wide distribution through the Americas, and particularly Latin America, have made it difficult to control vector-borne transmission of Chagas disease (WHO 2002). Triatoma dimidiata is one of the main vector taxa involved in Chagas transmission in Latin America, specifically the main vector for Central America and a secondary vector in Mexico and Colombia. Its broad geographic range and phylogenetic diversity have posed taxonomic challenges for many years (Dorn et al. 2007). Therefore, understanding the taxonomy, phylogenetic and ecological diversity of the T. dimidiata complex is important for understanding T. cruzi transmission.

Here we are presenting three lines of evidence that support T. huehuetenanguensis as a distinct species: morphological, nuclear genetic (ITS-2) and mitochondrial genetic (cytB). The morphological characters included in the taxonomic key for Triatoma species (Lent and Wygodzinsky 1979) for T. dimidiata encompass T. huehuetenanguensis, specifically overall size and measurements of the head and eyes. However, on closer examination, macroscopic differences, including those summarized in Table 4, reveal T. huehuetenanguensis as morphologically different. Color differentiation on connexivum, pilosity, ocelli, labial articles joints, and female and male terminalia separate T. huehuetenanguensis from T. dimidiata. Differentiation based on the color pattern of the connexivum and other body regions was used in the description of T. brailovskyi (Martinez, Carcavallo & Pelaez, 1984), T. gomeznunezi (Martinez, Carcavallo & Jurberg, 1994) and most recently Triatoma mopan (Dorn et al., 2018). This latter study attributed the diminished pigmentation of T. mopan as the result to the cave environment. In our case, where both, T. huehuetenanguensis and T. dimidiata are found in sympatry and in domestic environments, it would be interesting to determine the process that caused such color differentiation between these two species. Another important morphological character is the location and pigmentation of the spiracles. These structures in T. huehuetenanguensis are adjacent to the connexival suture, whereas in T. dimidiata, they are close but not adjacent to the connexival suture. Differentiation based on the location and color of the respiratory spiracles was reported in the description of Rhodnius montenegrensis (Rosa et al., 2012) and most recently in the description of Triatoma mopan (Dorn et al., 2018).

The phylogenetic molecular analysis from the nuclear ITS-2 and the mitochondrial cytB gene, recovered a single monophyletic clade with high support (Fig. 7), and low genetic divergence (<3.1% for cytb and < 0.6% for ITS-2) indicating that Triatoma dimidiata auct., non (Latreille, 1811), Triatoma sp. aff. dimidiata (Bargues et al. 2008), Triatoma sp. aff dimidiata group 3 (Monteiro et al. 2013, Dorn et al. 2016, Justi et al. 2018) and T. huehuetenanguensis are the same species (see Suppl. material 3: cytB maximum likelihood phylogeny and Suppl. material 4: ITS-2 maximum likelihood phylogeny). Previously published molecular phylogenies (Bargues et al. 2008, Monteiro et al. 2013, Dorn et al. 2016, Justi et al. 2018) have thoroughly described the ITS-2 and cybB diversity within and among the four groups that comprise T. dimidiata s. l. This allowed us to compare these two regions in two of the specimens used by Justi et al. (2018), and verify that they fall within the monophyletic clade. Two Triatominae species were differentiated based on molecular analysis of the mitochondrial gene (Cytb), R. montenegrensis (Da Rosa et al. 2012) and Rhodnius marabaensis (Souza et al. 2016).

Figure 7. 

Maximum likelihood cytB and ITS-2 phylogenies. Bootstrap support values of the relevant clades are shown. Habitus of T. huehuetenanguensis and related species are shown to scale (10 mm).

As supported by our genetic data, we suggest the inclusion of T. huehuetenanguensis in the subcomplex T. dimidiata. Based on Justi and Galvao (2017), this subcomplex is comprised by: T. dimidiata, T. hegneri, T. brailovskyi and T. gomeznunezi, and more recently T. mopan has been added (Dorn et al. 2018). The most relevant differences between these six species are summarized in Table 5.

Relevant Triatominae species for human T. cruzi transmission are those that have evolved to live close to humans and have been found to be infected T. cruzi (WHO 2002). Triatoma huehuetenanguensis was collected in both peridomestic and intradomestic environments. The high natural infection with T. cruzi (> 90% of the specimens) suggests it is a potentially important vector and its role in human Chagas disease should be further evaluated.