Hylomyrma transversa Kempf, 1973

Ulysséa, Mônica Antunes, 2021, Taxonomic revision of the Neotropical ant genus Hylomyrma Forel, 1912 (Hymenoptera: Formicidae: Myrmicinae), with the description of fourteen new species, Zootaxa 5055 (1), pp. 1-137 : 112-115

Hylomyrma transversa Kempf, 1973

Figures 71 , 72 , 80H , 89 (map)

Hylomyrma transversa Kempf, 1973: 250 (W, Q). Holotype: PERU: [Loreto]: Islandia, 23.ix.1962, W.L. Brown col., varzia, litter (1W) (MCZ35423) [ MCZC] [examined]. Paratypes: same data as holotype (1Q) (MCZ35423) [ MCZC] [examined]; (1W) ( MZSP67451 ) [ MZSP] [examined].

Diagnosis. 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.

Redescription. WORKER (n=4) ( Fig. 71A–C ): HL 0.98 (0.88–0.98); HW 0.90 (0.82–0.90); ML 0.58 (0.54–0.58); SL 0.68 (0.64–0.70); MOD 0.27 (0.24–0.28); PNW 0.64 (0.60–0.64); WL 1.26 (1.15–1.26); PSL 0.28 (0.22–0.28); PL 0.56 (0.48–0.56); PW 0.24 (0.22–0.24); PPL 0.31 (0.30–0.32); PPW 0.36 (0.33–0.36); GL 1.06 (1.04–1.06); TL 4.75 (4.40–4.80); CI 91.83 (90.81–93.18); SI 75.55 (75.55–78.65); OI 30 (29.26–31.46). Small-sized. Integument shiny to subopaque. Body light brown, head and gaster darker. Many long to short setae, appressed to decumbent; unbranched setae mostly on head dorsum and leg; branched setae with multiple branches arising from the main axis; branches relatively long, subequal in size ( Fig. 80H ); branched setae mainly in posterior and lateral regions of head, mesosoma, petiole and postpetiole.

Head subquadrate; posterior margin straight to slightly concave at middle. Mandible masticatory margin with 6 teeth. Anterior margin of clypeus straight medially, with a pair of medium teeth laterally; median area of clypeus with regular and longitudinal striae converging to a point on the anterior margin, interspaces indistinguishable. Frontal triangle with 1–3 striae. Short scape, not reaching head posterior margin; apical antennomere length 1 / 4 shorter than previous 3 antennomeres together. Frontal carina slightly concave posterior to antennal socket. Eye drop-shaped, midsized, larger diameter with 14 ommatidia. Regular and longitudinal striae on head dorsum, parallels towards posterior margin, interspaces between thicker striae filled with thinner and regular to irregular striae. Head lateral and laterodorsal regions with the same striation of head dorsum, striae converging to eye margin; gena striate, regular and semicircular striae circumscribe the torulus almost reaching eye margin. Interspaces between striae on head ventral surface distinguishable.

Mesosoma covered with striae of variable thickness assuming multiple directions, interspaces indistinguishable; transverse striae on pronotum anterior region (DV) continuing towards lateral of pronotum; longitudinal striae on promesonotal junction and metanotal groove; transverse striae on mesonotum; 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 mesonotum straight. Promesonotal junction and metanotal groove discernible by a depression and altered sculpture. Transverse carina inconspicuous. Dorsal margin of mesosoma discontinuous, dorsal margin of mesonotum straight. Propodeal lobe bidentate, dorsal tooth slightly longer and more acute than shorter and blunt ventral tooth; dorsal tooth length is 1 / 2 of propodeal spine length. Propodeal spine midsized, straight (LV), divergent (DV), sculptured on base. Procoxa with transverse striae of uniform thickness; irregular and transverse striae on C2 and C3. Transverse striae on profemur. Protibia extensor surface entirely striate.

Dorsal margin of petiole discontinuous; ventral surface entirely covered with transverse striae. Node with transverse striae on anterior surface continuing on lateral surface, interspaces distinguishable; regular to irregular and mostly transverse striae on dorsal surface, interspaces indistinguishable. Postpetiole and subpostpetiolar process with regular, longitudinal striae; subpostpetiolar process weak, straight to convex.

First gastral segment striation similar to postpetiole striae; striae length on tergum slightly longer than postpetiole length; sternite striation weakly marked, covering all basal region.

QUEEN (n=1, paratype) ( Fig. 72A–C ): HL 0.98; HW 0.90; ML 0.60; SL 0.70; MOD 0.28; PNW 0.70; WL 1.40; PSL 0.26; PL 0.59; PW 0.27; PPL 0.36; PPW 0.36; GL 1.22; TL 5.15; CI 91.83; SI 77.77; OI 31.11. Midsized. Color, pilosity, and some sculpture characters shared with conspecific workers, only slightly larger. Larger diameter of eye with 15 ommatidia. Longitudinal and regular striae on scutum going from an anterior central point towards transcutal suture, interspaces indistinguishable. Longitudinal striae on anepisternum and katepisternum with interspaces indistinguishable, striae regular on anepisternum and mostly irregular on katepisternum. Axilla with the same sculpture of scutum. Scutoscutellar sulcus conspicuous. Scutellum with the same sculpture of scutum, striae slightly irregular to vermicular on lateral regions. Transverse striae on propodeum (DV). Lateral of mesosoma with longitudinal and mostly regular striae directed to propodeal dorsum, interspaces indistinguishable. Wings unknown.

MALE Unknown.

Etymology. The name transversa (Latin, transversus = transverse) refers to the conspicuous transverse striae on mesonotal dorsum.

Comments. This species is easily distinguished from all congeners by the transverse striae on the mesonotum, and the conspicuous branched setae. Still, H. transversa resembles H. 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. All known specimens were collected in northwestern South America (Brazilian Amazon, Bolivia, Colombia, and Peru) ( Fig. 89 ).

Natural history. 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.

Additional material examined (27 workers, 8 intercastes): BOLIVIA: [La Paz]: Lower Rio Madidi , W.M. Mann, Mulford BioExpt 1921–22, January (7W 2I) [ USNM] ; same except Jan (4W 2I) [ USNM] ; Rio Negro , W.M. Mann collector, Mulford Biological Exploration 1921–22, Jan (2I) [ MZSP] ; same data (2W) [ CASC, DZUP] . [ BRAZIL]: AM[Amazonas]: Itacoatiara, 3.319°S, 58.723°W, PLOT 63—isca #15. J.M.S. Vilhena, 6/114/03 (1W) (MZHY193) [ MZSP] ; Novo Airão, PNJ R. Unini, mg. esq., com Lago Pedras , 1°38′25″S, 61°39′19″W, Mata Primária, 20–23.xi.1995, Bindá + Alencar, Pitfall trap #5 (1W) [ INPA] ; same except Pitfall trap #7 (1W) [ INPA] ; Tarumã-Mirim, 31.iii.1976, Joaquim Dias (1W) [ MZSP] ; Rio Negro , Arquipélago d. Anavilhanas, iii.76, R. Negre, #13186 (2W 2I, one worker covered with gold) ( MZSP67452 ) [ MZSP] ; PA[Pará]: Porto Trombetas, 01.08.92, Majer J.D., 4552, Jam76 (2W) [ CEPLAC] . COLOMBIA: Caquetá: [Puerto] Solano, PNN [Serranía de] Chiribiquete, R. Mesay, B. Caki , 300m, 0°14′24″N, 72°56′02″W, T. caída, T1.T3, 27.i.2000, F. Quebedo leg. (2W, one covered with gold) [ IHVL] ; same except T1.T2 (1W) [ MZSP] ; Cauca: Isla Gorgona , 14.xi.1987, M. Baena (1W) [ IHVL] ; Guaviare: RN Nukak Maku , 02°10′40N, 71°11′25W, Cñ Cucuy Cr Moyano, Rebalse, F. Fernandez F.E., feb. 96 (1W without postpetiole and gaster) [ IHVL] ; same data (1W) (MZHY221) [ MZSP] .

Figures

FIGURE 71. Worker of Hylomyrma transversa (MZSP67452). A) frontal view; B) dorsal view; C) lateral view. Photos by Ricardo Kawada.

FIGURE 72. Paratype queen of Hylomyrma transversa (MCZC35423).A) frontal view; B) dorsal view; C) lateral view. Photos by M.A. Ulysséa.

FIGURE 80. Types of setae found in the species of Hylomyrma. Unbranched setae: A) Hylomyrma adelae, H. blandiens, H. macielae; B) H. immanis; C) H. marielleae. Branched setae: D) H. dentiloba, H. lispectorae, H. mitiae, H. peetersi, H. virginiae; E) H. balzani, H. lopesi; F) H. blandiens, H. jeronimae, H. versuta; G) H. dolichops; H) H. transversa; I) H. longiscapa; J) H. balzani, H. lopesi, H. primavesi, H. reitteri, H. versuta; K) H. plumosa.

FIGURE 85. Distribution records of Hylomyrma columbica, H. marielleae, H. plumosa, and H. reitteri.

FIGURE 89. Distribution records of Hylomyrma lopesi, H. margaridae, H. peetersi, H. transversa, and H. virginiae.