Typhlomyrmex prolatus Brown, 1965

Fernandez, Fernando, Fiorentino, Gianpiero & Castro, Daniel, 2023, A new species of Typhlomyrmex from Colombia, re-description of the worker of T. clavicornis Emery, description of the worker of T. prolatus Brown, and key of known species (Hymenoptera, Formicidae), Journal of Hymenoptera Research 96, pp. 579-597 : 579

Typhlomyrmex prolatus Brown

Figs 3 , 6C

Typhlomyrmex prolatus Brown, 1965: 72, fig. 6 (queen.) Costa Rica.

Typhlomyrmex prolatus : Kempf, 1972: 256; Bolton, 1995: 422; Camacho et al. 2022: 12.

Material examined.

Colombia: Caquetá, Belén de los Andaquíes, 01°37'40.0"N, 75°54'16.8"W, 750 m, 28.i.2017, leg. D. Castro, 2 workers (CATAC-00879); Florencia, Vereda La Viciosa , CIMAZ Macagual, 01°28'46"N, 75°36'16"W, 260 m, 26.x.2019, leg. J. Perdomo, 1 worker (LEUA 00000050568) .

Worker description.

Head. Elongated; vertexal margin weakly concave; posterolateral corners narrowly rounded; sides of head weakly convex; clypeus medially dome-shaped, the dome conspicuously protruding from the lateral clypeal margins and with a vertical anterior face; clypeal margin medially convex; anterior clypeal lamella narrow, without a medial lobe; eyes reduced to one ommatidia situated near the middle of the capsule sides; antennal sockets partially concealed by the frontal lobes frontal carinae; frontal lobes short and subquadrate; toruli circular and definitely separated, visible by transparency through the frontal groove integument; antenna 12-segmented with a 3 segmented club; scape conspicuously bent ventrally at one third of its apical length in frontal view, the maximal width being nearly equal to the pedicel length; when folded backward, its apex reach the vertexal margin; pedicel about twice as long as wide, and about as long as the 2 following segments together; segments A3-A9 quadrate to wider than long; segment 10 to 12 forming antennal club; mandible shape elongated-subtriangular, the apical margin joining basal margin at a round angle; masticatory margin with 7-9 small teeth from base to apex before the bigger apical tooth.

Mesosoma. Sub-rectangular in lateral view; pronotum anteriorly rounded in dorsal view, a little wider than long and strongly sloping anteriorly in lateral view, its posterior part horizontal; promesonotal suture underlined by a weak furrow, forming an arch, widely concave posteriorly; promesonotal suture well marked in dorsal view; mesonotum almost flat dorsally; metanotal groove distinct but weak; sides of the propodeum weakly concave medially in dorsal view; metapleural gland orifice in profile as a short oblique slit, bounded below by a convex rim of cuticle that directs the orifice posterodorsally; the swollen bulla of the gland is visible through the integument, its anterior margin in touch with the propodeal spiracle; dorsal face of the propodeum weakly inclined and almost flat, gradually rounding beyond the spiracle towards the sloping posterior face; propodeal spiracle opened laterally and slightly downward, its large orifice bordered by a thin cuticular ring, its diameter (0.041 mm); propodeal lobes lacking.

Metasoma. Petiole short, higher than wide, shortly pedunculate and broadly constricted between abdominal pre- and postsegment; petiolar node broad, anterior face slightly concave in lateral view, the anterior apex sharp followed by a evenly curved posterior face; in dorsal face node trapezoidal, wider than long, posterior face strongly concave; spiracles on lateral protuberances near anterolateral base of node, their orifices circular, opening laterally and slightly posteriorly; sternite with a short medial carina lengthened anteriorly by a medium sized; subpetiolar process elongated triangular with a sharp point directed forward; gaster elongated, its maximal width at the level of abdominal segment IV; abdominal tergite III with a median short anterior carena strongly produced and seen in lateral view.

Sculpture. Cephalic capsule wholly sculptured with rugosities and punctuations; frons and vertex medially impressed by a narrow longitudinal band striae, from frontal lobes diffusely diverging just before the vertexal margin; the lateral margins of genae with weakly sinuous striae, almost all the dorsum of capsule is covered by scattered piliferous punctuations nearly aligned except on genae at the level of the antennal sockets, on the medial part of the frons and the vertex; punctuations denser dorsally than ventrally, conspicuously more impressed on the posterior two third of the capsule and especially dense at the transition between vertex and genae; mandibles smooth and shiny; pronotum and mesonotum with a dense piliferous punctuation except on a narrow median band and on anterolateral margins of the pronotum which are smooth and shiny; pronotum with narrow longitudinal smooth band; propodeum with a broad smooth and shining area widening toward the propodeal declivity; mesopleura with central area smooth and shining, nearly circular; propodeum finely striated and punctuated laterally but medially smooth and shining; petiole node dull with fine punctuations denser anteriorly and laterally, in lateral view mostly smooth and shining; gaster and femora entirely covered by sparse piliferous punctuation, weaker than on head and thorax.

Pilosity and color. Short and abundant on head and body. Erect hairs (longer than antennal segment 11) on clypeal dome, petiolar dorsum and gaster. Shorter erect hairs on most metasomal sterna; appressed pubescence formed by dense short setae, distributed on most of the body. Color: body reddish brown, antennae, and legs lighter.

Measurements. HW 0.578, HL 0.528, SL 0.464, PrW 0.307, PeW 0.239, PeL 0.314, PeH 0.305, WL 0.913, CI 109, SI 80, TL 1.85.

Diagnosis and comments.

This species is easily separated from any other Typhlomyrmex by the possession of the short protruding carina on the anterior dorsum of the first metasomal tergum. This trait is described in the female of the species in Brown (1965) where they posit that it may be present in the worker. All workers examined in this work share this characteristic, so the possibility that it is a pointing error or a mutation in the first specimen observed by Brown is clearly ruled out. The function of this structure, if it exists, is unknown. As far as we know, this structure is unknown in other ants within this genus.

Distribution.

Until this present work, the only confirmed localities of this species were in Central America ( Brown 1965; Mackay et al. 2004; Dáttilo et al. 2020); however, records for Brazil and Venezuela were mentioned by Lacau et al. (2008) without pointing out the records; our records and the literature records establish an altitudinal distribution from 50 m to 1,200. m for T. prolatus . With these records, along with our own presented herein, we confirm the presence of this species in South America. Confirmed records range from Mexico to Colombia, with the possibility of having a broader distribution (see discussion).

Biological notes.

Typhlomyrmex prolatus specimens examined in this study were collected exclusively in the soil at 0-10 cm depth; the collection substrate in previous records is unknown. This species has been found in fragmented rain forests in piedmont area. The individuals of CATAC-00879 were collected sharing the soil galleries with a colony of Anoplotermes meridianus .

Key to known Typhlomyrmex based on worker caste (modified from Lacau et al. 2004 and Camacho et al. 2020)

Worker of T. foreli unknown.

1	At least head frons with longitudinal striation or costulation	2
-	Head never with conspicuous costulation, striation, if present, faint and limited to lateral sides	5
2(1)	In dorsal view, mesosomal dorsum totally sculptured, usually costulate or rugulose	3
-	In dorsal view, mesosomal dorsum with large smooth and shiny areas	4
3(2)	In frontal view, scape not reaching the vertex margin; metacoxal dorsum with a lobe or denticle; in dorsal view, segments I and II of gaster (abdominal segments III and IV) covered by small ridges or striae, extending from the base of the hairs. Brazil	T. lavra (Lattke)
-	In frontal view, scape slightly surpassing the vertex margin; metacoxal dorsum unarmed; in dorsal view, segments I and II of gaster (abdominal segments III and IV) completely smooth and shiny. Brazil	T. lenis (Camacho et al.)
4(2)	Pronotum densely punctate, mesosoma lacking any striations; color generally yellow to light brown. Brazil	T. meire Lacau et al.
-	Pronotum densely costulate and striate, mesosoma with deep striations; color generally dark brown. Colombia and Venezuela	T. reichenspergeri (Santschi)
5(1)	Antennae 10 segmented, postpetiole (first metasomal tergum) with a distinct, sharp median carinae on the anterior third of its dorsal surface	T. prolatus Brown
-	Antennae with more than 10 segments, postpetiole without dorsal median tubercle or carena	6
6(5)	Anterior face of mesotibia with about 10 denticuliform erect setae (Fig. 4B ); mandible shape elongated-subtriangular, their basal margins weakly convex, not reaching the anterior clypeal margin at full closure. Bolivia, Brazil, Colombia, Guiana	T. clavicornis Emery
-	Anterior face of mesotibia without denticuliform setae (Fig. 4A, C ); mandible shape triangular, their basal margins rectilinear or weakly concave, fitting tightly against clypeus at full closure	7
7(6)	Petiole well pedunculate in lateral view; node poorly developed, longer than high, subconvex at its top and without a distinct posterior face; abdominal tergite III without obvious anterior face; size polymorphism marked. Neotropics	T. rogenhoferi Mayr
-	Petiole weakly pedunculate in lateral view; node well developed, higher than long, well rounded at its top and with a distinct posterior face; abdominal tergite III with a distinct anterior face; monomorphic	8
8(7)	Metafemora base (posterior view) sharply swollen ventrally, so that it forms a short vertical face at the base, joining the ventral face by an obtuse and rounded angle; head width>0.55 mm	T. major Santschi
-	Metafemora base (posterior view) poorly swollen ventrally, so that it does not form an angle at its base; head width <0.55 mm	9
9(8)	Clypeal lamella bearing a short and narrow median process, protruding, and clearly truncated at the apex (Fig. 5A ). Colombia	T. encanto sp. nov.
-	Clypeal lamella not bearing a short and narrow median process (Fig. 5B, C ). Widespread	T. pusillus Emery

Figures

Figure 3. Photomicrographs of Typhlomyrmex prolatus (CATAC- 00879) A head in frontal view B body in dorsal view C body in lateral view D postpetiolar carinae in dorsal view and E lateral view. Arrows pointing out the petiolar carinae. Scale bars: 0.25 mm (A, D, E); 0.5 mm (B, C).

Figure 4. Photomicrographs comparing the mesofemur and mesotibia of A T. encanto sp. nov. B T. clavicornis C T. prolatus. Arrow pointing out the highly modified spiniform setae found only in the mesotibia of T. clavicornis. Scale bars: 0.2 mm (A, C); 0.1 mm (B).

Figure 5. Photomicrographs comparing the clypeus of A T. encanto sp. nov. B T. clavicornis C T. prolatus. Arrow pointing out the highly modified clypeal projection found only in T. encanto sp. nov. Scale bars: 0.2 mm.

Figure 6. Distribution maps A Typhlomyrmex encanto sp. nov. B Typhlomyrmex clavicornis C Typhlomyrmex prolatus. Note: Literature record refers to records in the literature with coordinates available, records in literature without coordinates are not indicated in maps, but are mentioned in the distribution section of each species.