Strumigenys onorei

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Strumigenys onorei
Scientific classification
Kingdom: Animalia
Phylum: Arthropoda
Class: Insecta
Order: Hymenoptera
Family: Formicidae
Subfamily: Myrmicinae
Tribe: Attini
Genus: Strumigenys
Species: S. onorei
Binomial name
Strumigenys onorei
Baroni Urbani & De Andrade, 2007

Lattke, J.E hefa.jpg

Lattke, J.E hal.jpg

Synonyms

Lattke and Aguirre (2015) - The Arco Iris type collection site is located within Podocarpus National Park along the road that joins Loja with Zamora within dense montane cloud forest, bearing a canopy not more than 20 m high upon steep slopes. It is within the catchment area of the Río San Francisco, with an estimated average annual rainfall of 3500-4000 mm, relative cloud cover of 70-80% (Richter et al. 2013), and an estimated mean annual temperature of 15-16°C (Wilcke et al., 2008). The Reserva Madrigal locality is a private reserve that neighbors Podocarpus National Park approximately 7 km SSE from Loja. It was previously a dairy farm and has been undergoing restoration towards forest during the last ten years. The specimens were taken from several samples along a 200 m long transect in mostly secondary vegetation, ranging from trees approximately 15 m high forming a loose canopy to more open bracken (Pteridium sp.) dominated understory with scattered trees and shrubs. Neighboring slopes to the sampling site across the stream bear dense forest with a canopy apparently not more than 15 m high. The area has an estimated average annual rainfall of 3000-2500 mm (Richter et al., 2013).

Identification

Baroni Urbani & De Andrade (2007) - A member of the gundlachi complex in the Strumigenys gundlachi group. Resembling Strumigenys enopla but differing from it by the smaller SI values (≤ 79.5 instead of ≥ 84), by the shorter propodeal spines, by the postpetiole with the ventral spongiform process larger and by the standing hairs on head and gaster shorter.

The 15 species of the gundlachi-complex can be divided in 4 clusters of closely related species. S. onorei can be placed in the gundlachi s. str. cluster comprising the following 5 species: Strumigenys denticulata, Strumigenys eggersi, Strumigenys enopla, Strumigenys gundlachi and Strumigenys jamaicensis. Among these five species, onorei resembles enopla, and both species share the SI ≥ 79-100. Of the other species of the gundlachi complex, only some specimens of jamaicensis and denticulata may have SI 80-81, but jamaicensis differs from onorei and enopla by the strongly developed preapical dentition (inconspicuous in onorei and enopla) and by the larger spongiform process of postpetiole, while denticulata differs from both, onorei and enopta by the pair of erect hairs on the mesonotum shorter and stiff instead of long and flagellate and by the spongiform process of postpetiole much more reduced or absent. S. onorei differs from all the 5 species mentioned above by having the smallest propodeal teeth and probably also by the mesonotum with 2 pairs of erect hairs instead of one (see the description). By using the identification key by Bolton (2000) for the Neotropical species of Pyramica, S. onorei will fall in the couplet 26 where it can be differentiated from jamaicensis by using all characters of the first couplet and excluding only “head slightly shorter and broader, CI 77-85”, and from enopla by the following characters: SI < 80, standing hairs on the head about as long as the eye length, spongiform process of the postpetiole at least 1/3 as height to the exposed cuticle of side of postpetiole disc.

A member of the gundlachi-complex in the Strumigenys gundlachi group.

Lattke and Aguirre (2015) - Mandibles straight with small relatively same-sized 5-7 preapical denticles along anterior half; mandibular apex with two minute intercalary denticles that appear midway between upper and ventral apical teeth. Disc of postpetiolar dorsum weakly reticulate-punctate, spongiform processes of postpetiole well-developed. Head, most of mesosoma, coxae, femora and tibiae densely reticulate-punctate; katepisternum mostly smooth and shining.

This species fits quite well within the gundlachi-complex as defined by Bolton (2000:176) but the spongiform processes of the postpetiole are much more developed in S. lojanensis. Within the gundlachi-complex, S. lojanensis fits comfortably into the gundlachi species cluster, with the only difference consisting in the weaker reticulate sculpturing of the postpetiolar dorsum. Using the key to Neotropical Pyramica in Bolton (2000:137) specimens of S. lojanensis will flow directly to Strumigenys enopla. Using the description of S. enopla (Bolton, 2000: 185) and images of a Paratype from Antweb (CASENT0900177) it was possible to identify a number of discrete differences between the two species: The cephalic subdecumbent pilosity is not as arched and high as in S. enopla; the subdecumbent hairs on the mesosomal dorsum are also higher and more arched in S. enopla, as well as the standing hairs on petiole, postpetiole and gaster. The mesosomal dorsal margin of S. lojanensis is straight in lateral view, whilst in S. enopla it lojanensis than in S. enopla. There are 2 standing hairs on the petiolar dorsum of S. lojanensis, compared with 4 in S. enopla. In S. enopla the posterior edge of the spongiform sculpturing on the postpetiole is convex, but in S. lojanensis there is a distinct low median lobe.

The reticulate-punctate sculpture of the postpetiole is mostly strong and comparable to that of the petiole, covering most of it but weakens posteromedially on the dorsum, so it could be difficult to decide which way to go at couplet 7 of Bolton’s key. If the user decides for first option then the specimen will become stranded at couplet 9 due to the number of denticles, exceeding the maximum amount for either option. If the modification of Bolton’s key proposed by Rigato and Scupola (2008: 481) is used, then the specimen will key directly to Strumigenys osellai. In this case differences in the preapical dentition and metapleural sculpturing will permit easy separation: S. lojanensis bears only small denticles and never a large pair of denticles, plus the metapleuron in S. osellai is smooth and shining, but not so in S. lojanensis.

Keys including this Species

Distribution

Distribution based on Regional Taxon Lists

Neotropical Region: Ecuador (type locality).


Distribution based on AntMaps

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Distribution based on AntWeb specimens

Check data from AntWeb

Biology

Lattke and Aguirre (2015) - With the discovery of S. lojanensis it is possible to discern a group of 5 northern andean species of the gundlachi complex with a preference for cold forests above 2000 m altitude, where the presence of most ants is negligible (Longino, 2014). The other species are Strumigenys enopla, known from altitudes between 1900 and 2200 m in SW Colombia, Strumigenys nubila, sampled from altitudes between 2000 and 2500 m in Colombia and Venezuela, Strumigenys vartana, a Colombian species known from altitudes between 1800 and 2530 m and Strumigenys heterodonta which was recently described from 2940 m altitude in Ecuador (Rigato & Scupola, 2008).

Are these cold weather specialists closely related? Do they form a monophyletic group? Bolton recognizes two complexes of species within the gundlachi-group based upon the mandibular dentition and the development of the apical lobes of the labrum and their accompanying trigger hairs: the crassicornis complex, and the gundlachi complex. Bolton (2000) informally divides the gundlachi complex into four clusters of apparently related species using the mandibular index, number and position of intercalary denticles of the mandibular fork, number and position of the preapical mandibular dentition, configuration of the main pilosity, and sculpture of the postpetiolar node. In his scheme both S. enopla and S. lojanensis fit in the gundlachi cluster, where they are the only cloud forest specialists, though widely distributed species such as Strumigenys denticulata, and S. gundlachi also have broad altitudinal ranges that include cloud forests but none approaching 2000 m (Bolton, 2000; Lattke & Goitia, 1997). S. vartana lies in the laevipleura cluster, which includes Strumigenys gemella Kempf recorded from cloud forests in Colombia close to 1700 m (Bolton, 2000). Strumigenys nubila shares the nubila cluster along with Strumigenys lalassa, a species found from sea level to 1500 m from Costa Rica to Ecuador (Bolton, 2000). Rigato and Scupola (2008) described Strumigenys heterodonta as part of the gundlachi complex, and opted for placing it in fifth species cluster as they were not satisfied with its affinities to any of the other species. Nevertheless S. heterodonta is quite comparable with the nubila cluster as it fits most of the traits used by Bolton, the differences being more of a degree than categorical. Most of the seven species of the subedentata cluster are found in low to medium altitudes except for Strumigenys connectens, known from forests close to 1500 m in Ecuador (Bolton, 2000), and Strumigenys paniaguae found in Costa Rica between altitudes of 500-1500 m (Longino, 2006). A brief overview of the ten species making up the crassicornis complex (Bolton, 2000) shows most of them to inhabit low to medium altitudes except for Strumigenys pasisops, found in cloud forests of 1500 m, so it seems that the cold weather (>2000 m) specialists are, for the while being, restricted to the gundlachi complex, implying some close relationship.

Castes

Nomenclature

The following information is derived from Barry Bolton's New General Catalogue, a catalogue of the world's ants.

  • onorei. Strumigenys onorei Baroni Urbani & De Andrade, 2007: 143, fig. 50 (w.) ECUADOR.
    • Senior synonym of lojanensis: Lattke et al., 2018: 146.
  • lojanensis. Strumigenys lojanensis Lattke & Aguirre, 2015: 176, figs. 1-3 (w.q.) ECUADOR.
    • Junior synonym of onorei: Lattke et al., 2018: 146.

Unless otherwise noted the text for the remainder of this section is reported from the publication that includes the original description.

Description

Worker

TL 2.10-230; HL 0.49-0.54; HW 0.39-0.43; SL 0.31-0.34; ML 0.37-0.39; EL 0.06; WL 0.52-0.58; CI 79.0; SI 79.1-79.5; MI 72.2-75.5.

Head strongly converging anteriorly and with round vertexal corners. Frontal lobes slightly expanded, and convex. Antennal fossae ventrally with a marked carina visible in full-face view, straight, covering the lower margin of the scrobes and ending close to the upper border of the eye. Eyes with 3-4 ommatidia in the longest row, placed over the ventral margin of the antennal scrobes, and partially visible in dorsal view. With the head in profile the scrobe distinct, with the upper margin more marked than the lower one. Lateral clypeal margins gently converging anteriorly into a straight margin. Scapes slightly compressed dorsoventrally, with weak sub-basal bend, about 2/3 of the head length and surpassing the eyes posteriorly. Antennae with six segments. Apical funicular joint slightly longer than the rest of the funiculus. Mandibles elongate. Apical fork of the mandibles with two teeth and with two intercalary denticles. Preapical dentition consisting of a row with 4-6 minute denticles.

Mesosoma in profile gently sloping posteriorly. Propodeal teeth small and triangular; declivous propodeal face with a narrow lamella.

Petiole with a long pedicel and with the node high and convex. Ventral surface of the petiole without spongiform lamina. Petiolar node with marked posterior margin and without spongiform process. Postpetiole gently convex in profile. Postpetiole with marked anterior face; lateral and posterior faces surrounded by narrow spongiform processes slightly broader on the posterior face. Ventral surface of the postpetiole with spongiform process shorter than the height of the node in profile.

Gaster oval and with few, short costulae. Base of the first gastral tergie with narrow, spongiform pad.

Sculpture. Head, mesosoma, petiole and postpetiole reticulate-punctuate. Lower mesopleurae and gaster smooth.

Pilosity. Head and mesosoma with subdecumbent or decumbent, weakly remiform hairs, rarer on the pronotum and mesonotum, missing on the propodeum. Apicoscrobal hair long and flagellate. Cephalic dorsum with two pairs of standing hairs, one close to the vertexal margin and the other close to the highest point of the vertex. Pronotal humeral hair long and flagellate. Mesonotal dorsum with 1 pair of erect, flagellate hairs. The holotype shows on the left side of the mesonotum one erect stiff hair before the flagellate one. This hair is missing in the unique paratype worker. Petiole, postpetiole and first gastral tergite with erect, sparse, weakly remiform hairs slightly longer on the gaster. Posterior half of the first gastral sternites and remaining sternites with appressed and erect pointed hairs.

Colour. Dark brown-black.

Description of Strumigenys lojanensis

Worker

Holotype (Paratypes, n=4): HL 0.62(0.60-0.63), HW 0.47(0.46-0.50), ML 0.49(0.48-0.50), SL 0.43(0.40-0.43), PW 0.31(0.31-0.34), AL 0.67(0.66-0.69) mm; CI 76(74-79), MI 79(76-82), SI 91(0.82-93). Posterior cephalic margin deeply concave, occipital lobes well developed; surface of cephalic dorsum transversely convex; anterior clypeal margin transverse, slightly sinuate with low median convex lobe. Dorsolateral margin of head with flagellate hair just posterad of eye level; cephalic dorsum with two pairs of slightly spatulate erect hairs, highest pair close to posterior cephalic border whilst shorter pair close to eye level. Leading edge of scape with slender hair at base that arches apicad, followed by 5 thicker, spatulate hairs: second hair from base arches apicad and is more slender than hairs 3-6, hairs 3-4 arch basad and hairs 5-6 usually arch apicad, though some specimens may have hair 6 arching towards base. Apical lobes of labrum clearly visible with mandibles closed, short and converge towards each other, slightly wider at base than at blunt apex; trigger hairs extend anterad to midpoint of mandibular length. Mandible straight, external margin straight to weakly convex, internal margin weakly sinuate, basally convex and apically concave, basal lamella convex; preapical denticles 5-6 on left mandible and 5-7 on right mandible with mandible pointing towards observer; denticles closest to apex usually larger though minute denticles or stubs may be present. Mandibular apex with two minute intercalary denticles that appear midway between upper and ventral apical teeth.

Mesosoma in lateral view with pronotal margin broadly convex, mesonotal to propodeal margin relatively flat. Transverse section of pronotal dorsum broadly convex; pronotal humeral hair fine and flagellate, sometimes forming apical loop; mesonotum with single pair of flagellate hairs; propodeal spiracle separated from posterior edge of propodeal lamella by over single width; propodeal tooth triangular, apex pointed. Propodeal tooth triangular, sharply pointed and slightly higher than basal length; metapelural lobe bluntly triangular, not higher than propodeal tooth. Petiole lacking spongiform processes, ventrum with low anterior lamella that extends posterad to midlength; spongiform sculpturing well-developed on postpetiolar ventrum and posterolaterally, vestigial strands of spongiform sculpturing usually present along anterior margin of abdominal sternite IV. Postpetiolar tergite with narrow lamella along anterior margin. Dorsum of abdominal segments II – V with series of straight to weakly arched hairs, all semi-erect over cuticular surface. Petiolar node with posterior pair, postpetiole with 3 pairs, two dorsal pairs and a lateral pair. Anterior border of abdominal tergite IV with transverse arched crest that parallels posteriorly projecting lamella of postpetiole, a few brief longitudinal costulae may be present along this crest; most of tergite smooth and shining with 20-24 erect, slightly arched, spatulate hairs and no appressed pubescence.

Head, most of mesosoma, petiole, postpetiole, coxae, femora and tibiae densely reticulate-punctate, sculpturing attenuated on discal area of postpetiolar node and along its anterior margin; katepisternum mostly smooth and shining with strip of reticulate-punctate sculpture along anteroventral and ventral margins, propodeal declivity mostly smooth and shining posteriorly; abdominal tergite IV smooth and shining. Body mostly dark brown, almost black; mandibles, antennae, and legs brown.

Queen

(Gyne 1 - Gyne 2): HL(0.62-0.64), HW(0.5-0.51), ML(0.51-0.48), SL(0.41-0.41), PW(0.38-0.39), AL(0.77-0.77) mm; CI(81-80), MI(82-75), SI(82-80). Besides the expected morphological differences the gyne is quite comparable to the workers except for the better developed petiolar ventral lamella, although still low it bears more resemblance to spongiform sculpturing whilst in the worker it is simply a brief, low lamella.

Type Material

Strumigenys onorei - Holotype. Ecuador, Loja, Reserva El Madrigal, 4.04655°S 79.17583°W, 6.3 km SSE of Loja, 2350m, 28 August 2014, J. Lattke 3590-14. Holotype (worker) deposited in Museo de Zoologia. Paratypes. (1) One worker and one queen from the same sample as the holotype also deposited in QCAZ. (2) Same locality data and date as the holotype: sample Lattke 3590-15 1w in Royal Belgian Institute of Natural Sciences. (3) Same locality data and date as the holotype: sample Lattke 3590-03 1w in Coleção Entomológica Pe. Jesus Santiago Moure, 1w in Insect Collection, Instituto de Ciencias Naturales, 1w in Museum of Comparative Zoology, 1w in Museu de Zoologia da Universidade de Sao Paulo. (4) Ecuador, Loja, Estación Fundación Arco Iris, Loja – Zamora road, km 23, 3.98846°S 79.09326°W, 12.12k E of Loja, 2105m, 18 August 2014, J. Lattke 3573. From sifted leaf litter sample. One dealate queen and 1 worker deposited in CISEC.

Strumigenys lojanensis - Holotype worker from Ecuador labelled: Banos de Agua Santa, Provo Tungurahua, 01°24'S 78°25'W, 1860 m, scndero Bella Vista, leaf-litter, 26.VIII.2004, Juan Manuel Vieira Correa (Museo de Zoología, Escuela de Biología). Paratype: 1 worker, same data and collection as the holotype.

Etymology

This species is named after Prof Dr Giovanni Onore as a sign of gratitude for his multiple helps during our fieldwork in Ecuador.

References