Forelius heyeri ( Forel 1902 ) Guerrero, 2021

Guerrero, Roberto J., 2021, Transfer of two South American ant species from Tapinoma Foerster 1850 to Forelius Emery 1888 (Hymenoptera: Formicidae: Dolichoderinae), Zootaxa 4920 (3), pp. 428-438 : 433-434

Forelius heyeri ( Forel 1902) comb. nov.

( Figs 5–10 )

Tapinoma heyeri Forel 1902: 296 . Syntype workers [two workers], S„o Leopoldo , Rio Grande do Sul, Brazil (Heyer) [ MHNG, examined]. One syntype worker (CASENT0909771) here designated lectotype.

Tapinoma heyeri var. risii Forel 1912: 58 . Holotype worker (by monotypy), Montevideo, Uruguay (D. Ris) [MHNG, examined] (CASENT0909772).

Forelius breviscapus var. pusilla Santschi 1922: 374 . Syntype worker(s), Cordoba , Argentina (Biraben) [NHMB, AntWeb image of syntype examined, CASENT0911547].

Forelius pusillus Santschi. Status as species, senior synonym of Forelius tucumanus ( Kusnezov 1953) : Cuezzo 2000: 263. Junior synonym of F. heyeri (syn. nov.): present study.

Forelius heyeri risii (Forel) . Combination in Forelius (comb. nov.) and junior synonym of F. heyeri (syn. nov.): present study.

Neoforelius tucumanus Kusnezov 1953: 330 , figs. 1–12. Holotype male, nontype workers, queens: Argentina, Tucumán, 14 Dec 1949 (Kusnezov) [not examined]. Junior synonym of Forelius pusillus Santschi : Cuezzo 2000: 263.

Forelius tucumanus (Kusnezov) . Combination in Forelius: Shattuck 1992: 95 . Junior synonym of F. heyeri : present study (syn. nov.).

Additional Material examined. Uruguay: Lavalleja; 34º17’02.6”S 55º15’27.7”W; 4 m; manual collection; 07.Jun.2016; foraging on coarse sand dune; RJ Guerrero RJGF-0185 (3w) ( CBUMAG) .

Additional specimen images examined, provided by www.antweb.org. Paraguay: Canindeyú, Tendal , 24°12’20.112”S 55°33’57.167”W; 212m; 20.Nov.2002. A.L. Wild AWL1710 (1w) ( ALWC). CASENT0173739 .

Worker measurements. Lectotype: HL 0.57, HW 0.51, SL 0.47, WL 0.69, CI 90, SI 92.

Other material (n= 7): HL 0.45–0.53, HW 0.39–0.51, SL 0.32–0.43, WL 0.48–0.68, CI 83–96, SI 80–91.

Diagnosis. Posterior cephalic margin completely straight. Mandible with five teeth and one denticle. Scape much shorter (± 0.43 mm) than that of F. antarcticus (SL Ż 0.69 mm), below or barely reaching the posterior cephalic margin by a length less than the width of the pedicel. Pronotum with two thick dark erect setae that contrast with the light integument, each seta arising from a distinct fovea.

Description. Head slightly longer than broad to subquadrate, with subparallel sides, slightly straight above the middle of the eyes to almost the most posterior region of the head where the margin curves inward; posterolateral corners blunt but differentiated; dorsal and ventral faces flattened, surface finely punctate and covered with abundant, very short, decumbent setae; four long erect setae arising from between the frontal carinae; eyes flattened, relatively large (~ 0.16 mm), and located within the head capsule some distance from the lateral margin in frontal view; maxillary palps long and digitiform, reaching the middle of the occipital foramen, 2nd to 6th segment almost the same length. Mandibles relatively wide, with well differentiated semiparallel external and basal margins; masticatory margin reddish and armed with a very long, pointed and falcate apical tooth, followed by a subapical tooth ¼ of the length of the apical, a third tooth of equal size to the subapical, a fourth tooth followed by robust denticle, a diastema crenulate, and usually a small basal tooth; mandibular surface smooth and opaque, with widely spaced setae and coarse foveae. Clypeus with the anterior margin entire and convex; with setae of relatively equal length directed downwards, a very long median clypeal seta (0.14 mm in the Lectotype), curved downwards just beyond the closed mandibles and flanked by two shorter frontally directed setae. Antennae with scapes slightly widening distally; pedicel elongated, almost twice the length of the second flagellomere, 2nd to 7th flagellomeres semirectangular and equal in length, the remaining four increasing in length and width, with the last flagellomere very enlarged and almost twice the length of the preceding one; abundant short, decumbent and separate setae.

In lateral view, promesonotum continuous, slightly elevated in the region where these sclerites join, mesonotum flat, in lateral view metanotal groove marked but not deeply impressed, mesonotum and propodeum almost continuous with a slight sinuosity where meet them (in dorsal view fully fused); dorsal face of the propodeum almost the same length as the propodeal declivity, without an angle that differentiates the two faces; spiracle large and circular, aligned with upper margin of propodeal declivity; dorsum of head with long, thin appressed hairs, integument with very short, spaced hairs; mesopleuron and part of the metapleuron smooth and shiny, the latter with a few long yellow hairs separated from each other, extending over the surface of the metapleural bulla.

Petiolar scale very small, projecting forward, generally concealed by the front of the first gastral segment; gaster surface finely punctate, pilosity like that of the head; first and second gastral terga with no erect setae, third and fourth gastral tergites with four and six thick erect setae, respectively; gastral sternites 1–4 with 3 to 4 erect setae on each plate, the last sternum with two central setae.

Dull yellow to light yellowish brown throughout the body.

Comments. The name Tapinoma heyeri is transferred to the genus Forelius as the type workers have a completely convex and entire anterior margin of the clypeus, and they have three long setae on the anterior clypeal vertex which are equal in length to the semi-closed mandibles. Furthermore, the masticatory margin of the mandible bears five conspicuous teeth and two denticles, and the basal margin is smooth and differentiated from the masticatory margin by an acute angle.

Although the type specimens of Forelius heyeri and F. heyeri risii differ in size, they both share two pairs of long thick setae on the dorsum of the head, the first pair on the oblique-lateral side of the posterior portion of the clypeus, and the second pair near to the upper end of the frontal carinae. In both cases the setae are directed anteriorly. Both taxa have a continuous mesosomal profile, with the posterior end of the propodeum rounding evenly into the oblique posterior face, and short and appressed setae on the surface of the body. Two erect pronotal setae are visible in F. heyeri , but in the type specimen of F. heyeri risii these are difficult to evaluate (CASENT0909772). Three workers collected in Lavalleja ( Uruguay) are relatively similar to the type F. heyeri risii but all bear the pair of erect pronotal setae found on the type of F. heyeri .

There are morphometric differences between the specimens associated with both names ( Fig 11 ). The type of F. heyeri risii is much smaller than the type of F. heyeri (WL = 0.49 vs. 0.69, respectively). The head of F. heyeri is broader (CIŻ 90), with subparallel sides converging slightly anteriorly, and a straight vertex with an almost impeceptible medial depression, while the head of the worker of F. heyeri risii is narrower (CI= 83), with convex lateral margins, continuing in a straight vertex. Both specimens also differ in the length of the scape relative to head width. In F. heyeri the scape is relatively long (SI = 81–83) surpassing the vertex by a very short distance, just 0.04 mm, while in F. heyeri risii the apex of the scape is well below the cephalic vertex (SI = 67). The coloration is variable among the specimens studied, from dull yellow in F. heyeri to light brown in F. heyeri risii . Although the type specimens show differences, the specimens recently collected in Uruguay show a relative continuity in the morphological and metric traits between the types of F. heyeri and F. heyeri risii ( Fig 11 ).

Cuezzo (2000) raised F. pusillus Santschi to the species level, offering a diagnosis and measurements that differentiated this Forelius species from all other species in South America. The taxonomic delimitation of F. pusillus by Cuezzo (2000) together with the measurements recorded here from a type specimen of F. pusillus and a non-type worker from Paraguay (measurements generated from images with codes CASENT0911547 and CASENT0173739, respectively) were compared with the diagnosis and description provided here for F. heyeri . Forelius pusillus and F. heyeri fully agree in their morphology as follows: the workers of F. pusillus also have two thick, erect pronotal setae, as well as a mesosomal profile similar to that found in F. heyeri ; the measurements are relatively variable throughout the distribution of these two putative taxa, with a similar morphometric space between those named F. heyeri risii and F. pusillus , but the nest-mate workers collected in Uruguay agree as much with those of F. heyeri as those of F. pusillus ( Fig 11 ). In this sense, I do not find morphological evidence to differentiate between these taxa and I propose F. pusillus as junior synonym of F. heyeri .

Figures

FIGURE 11. Bivariate plot relating the head length (HL) to both the head width (HW, left) and the scape length (SL, right) of Forelius heyeri. Small circles: three workers from a series recently collected in Uruguay. Medium circle: second syntype of F. heyeri. Large circle: F. heyeri lectotype. Square: F. heyeri risii lectotype. Small triangle: worker from Paraguay identified as F. pusillus on AntWeb (CASENT0173739). Large triangle: syntype of F. pusillus.

FIGURE 5–10. Forelius heyeri workers; type specimens of F. heyeri and its junior synonyms (F. heyeri risii and F. pusillus). 5–6) Full face view of the head, and profile of the Forelius heyeri lectotype worker (CASENT0909771). 7–8) Full face view of the head, and profile of the Forelius heyeri risii holotype worker (CASENT0909772). 9–10) Full face view of the head, and profile view of the Forelius pusillus syntype worker (CASENT0911547). Images 5–8 by Zach Lieberman, and images 9–10 by Will Ericson. All images from www.antweb.org.