Hylomyrma transversa

This species inhabits areas of tropical rainforest. Five specimens were collected with pitfall traps, and another was allured by an attractive bait, which suggests that workers forage on forest floor and that nests are located in fallen logs, rotten wood, between leaves, or inside natural cavities of the superficial soil layers. (Ulyssea & Brandao, 2021)

Identification
Regular and longitudinal striae on head dorsum, parallel towards posterior margin, interspaces between thicker striae filled with thinner striae; mesosoma covered with striae of variable thickness assuming multiple directions, interspaces indistinguishable; transverse on mesonotum; dorsal margin of mesonotum straight; lateral of pronotum and mesepisternum with longitudinal striae in part continuing transversely on propodeum dorsum and in part continuing on propodeal spine; dorsal margin of petiole discontinuous; petiole ventral surface entirely covered with transverse striae; regular to irregular and mostly transverse striae on dorsal surface of petiole, interspaces indistinguishable; subpostpetiolar process striate; profemur posterior surface and protibia extensor surface entirely striate; long striae on tergum of first gastral segment; sternite striation weakly marked, covering all basal region; branched setae with multiple branches arising from the main axis; branches relatively long, subequal-sized; branched setae mainly in posterior and lateral regions of head, mesosoma, petiole and postpetiole.

This species is easily distinguished from all congeners by the transverse striae on the mesonotum, and the conspicuous branched setae. Still, H. transversa resembles Hylomyrma reitteri, regarding the discontinuous dorsal margin of petiole, and the head pattern of sculpturation. The two species are allopatric and have broad distributions; H. transversa occurs in the center-northwest of South America (Fig. 89), and H. reitteri in the center-southeast of South America (Fig. 85).

Hylomyrma transversa can be easily distinguished from H. reitteri (characteristic in parentheses) in the drop-shaped eye (vs. reniform), the transverse striae on the mesonotal dorsum (vs. longitudinal striae), and the striate ventral surface of petiole (vs. smooth surface).

Specimens of H. transversa collected at Colombia’s Parque Nacional Natural Serranía de Chiribiquete have slightly thicker setae, lack branched setae, and the transverse striae on the mesonotum are more weakly marked. We found ten intercastes among specimens examined (four from Arquipélago de Anavilhanas, AM, Brazil; two collected at Rio Negro, and four sampled at Lower Rio Madidi, both in Bolivia), identified as such for being slightly larger than workers [(n=2), HL (0.98); HW (0.90–0.98); ML (0.60–0.64); SL (0.68–0.72); MOD (0.26–0.28); PNW (0.62–0.72); WL (1.24–1.30); PSL (0.24–0.28); PL (0.52–0.58); PW (0.22–0.28); PPL (0.30–0.32); PPW (0.32–0.37); GL (0.94–1.13); TL (4.64–5.02)]; for having one central ocellus, and a discernible promesonotal junction and metanotal groove by a conspicuous depression. Moreover, the specimens from Lower Rio Madidi, Bolivia, have small protuberances on the mesonotum, in the region where wings would be inserted in queens.

Distribution based on Regional Taxon Lists
Neotropical Region: Bolivia, Brazil, Colombia, Peru.

Nomenclature

 * . Hylomyrma transversa Kempf, 1973b: 250, fig. 9 (w.q.) PERU.
 * Type-material: holotype worker, 1 paratype worker, 1 paratype queen.
 * Type-locality: holotype Peru: Loreto, Islandia, 23.ix.1962, litter (W.L. Brown); paratypes with same data.
 * Type-depositories: MCZC (holotype); MCZC, MZSP (paratypes).
 * Status as species: Kutter, 1977a: 88; Brandão, 1991: 346; Bolton, 1995b: 213; Bezděčková, et al. 2015: 117; Pierce, M.P., Branstetter, et al. 2017: 137; Ulysséa & Brandão, 2021: 112 (redescription).
 * Distribution: Bolivia, Brazil, Colombia, Peru.

Type Material

 * Holotype: PERU: [Loreto]: Islandia, 23.ix.1962, W.L. Brown col., varzia, litter (1W) (MCZ35423) [MCZC] [examined by Ulyssea & Brandao (2021)].
 * Paratypes: same data as holotype (1Q) (MCZ35423) [MCZC] [examined]; (1W) (MZSP67451) [MZSP] [examined by Ulyssea & Brandao (2021)].

References based on Global Ant Biodiversity Informatics

 * Bezdeckova K., P. Bedecka, and I. Machar. 2015. A checklist of the ants (Hymenoptera: Formicidae) of Peru. Zootaxa 4020 (1): 101–133.
 * Brandao, C.R.F. 1991. Adendos ao catalogo abreviado das formigas da regiao neotropical (Hymenoptera: Formicidae). Rev. Bras. Entomol. 35: 319-412.
 * Fernández F., E. E. Palacio, W. P. Mackay, and E. S. MacKay. 1996. Introducción al estudio de las hormigas (Hymenoptera: Formicidae) de Colombia. Pp. 349-412 in: Andrade M. G., G. Amat García, and F. Fernández. (eds.) 1996. Insectos de Colombia. Estudios escogidos. Bogotá: Academia Colombiana de Ciencias Exactas, Físicas y Naturales, 541 pp
 * Fernández, F. and S. Sendoya. 2004. Lista de las hormigas neotropicales. Biota Colombiana Volume 5, Number 1.
 * Pierce M. P., M. G. Branstetter, and J. T. Longino. 2017 . Integrative taxonomy reveals multiple cryptic species within Central American Hylomyrma FOREL, 1912 (Hymenoptera: Formicidae). Myrmecological News 25: 131-143.