Monomorium humilior Forel 1910

Sparks, Kathryn S., Andersen, Alan N. & Austin, Andrew D., 2014, Systematics of the Monomorium rothsteini Forel species complex (Hymenoptera: Formicidae), a problematic ant group in Australia, Zootaxa 3893 (4), pp. 489-529 : 507-509

Monomorium humilior Forel 1910 stat. rev., stat. nov.

( Fig. 5 j–l, 9g –l, 11d)

Monomorium rothsteini var. humilior Forel 1910:27–28 .

Syntypes, 3 workers and 1 queen, Northern Territory, Tennant Ck , J.F. Field ( MHNG). One worker with label 269 here designated lectotype. The remaining specimens here designated as paralectotypes.

Chelaner rothsteini humilior (Forel) ; Ettershank, 1966: 97.

Monomorium rothsteini humilior Forel ; Bolton, 1987: 300–301.

Monomorium rothsteini Forel ; synonymy by Heterick, 2001: 408.

Diagnosis. A medium sized amber orange to orange brown species with a concave to sinuous clypeus, most specimens with a smooth, raised posterior mesonotum.

Worker measurements (n=9). HW 0.86–1.03, HL 0.88–0.99, EL 0.18–0.2, PMH 0.35–0.39, PH 0.29–0.33, PNH 0.21–0.23, LHW 0.57–0.60, EW 0.11–0.13, PML 0.57–0.62, ML 0.92–1.01, PL 0.41–0.47, PNWdv 0.23–0.27.

Worker Description: Medium sized species with a medium sized, square head; posterior cephalic margin straight. Anterodorsal margin of the clypeus somewhat variable: concave with frontolateral carinae forming raise, angular ridges that clearly extend beyond anteroventral clypeal margin as obtuse angles or concave to sinuous with frontolateral carinae forming smooth ridges that barely extend anteriorly beyond anteroventral clypeal margin. Anteroventral margin of the clypeus without a small median projection, margin appears straight. Sculpture on frons strigate, extending well above antennal lobes or restricted to antennal lobes and area in between; coarse lateral cephalic strigae reach anterior eye margin. Eyes medium, EW 0.20–0.23 x LHW, 11–12 ommatidia in longest vertical axis, 10 in longest horizontal axis.

Mesonotum rugulose/strigate on lateral curvature and in metanotal groove, remainder smooth, rarely with strigulae extending onto posterior mesonotum which appears raised in some specimens. Mesopleuron alveolate with strigulae extending anteriorly from metanotal groove in dorsal. Propodeum in lateral view with dorsolateral angles clearly forming an obtuse angle or rounded; laterally alveolate with strigulae extending over metapleural gland bulla, not reaching metanotal groove; most specimens with strigulae extending posteriorly from metanotal groove, reaching at least half way to spiracle; dorsal surface with anterodorsal transverse carina weakly present, transverse strigae present, longitudinal strigae present as broken, convergent lines. Petiole node of moderate width, 2 and 2.5 x eye width when viewed from above; shape in posterior view tapering from midline to broadly rounded apex or cuneate in specimens around Alice Springs, in lateral view anterior and posterior faces converging, apex broadly rounded from higher anterior face to lower posterior face when viewed laterally. Petiole and postpetiole finely reticulate in most specimens, dorsally smooth, some specimens with sculpture restricted to basal half of petiole node. T1 finely reticulate over entire surface or with sculpture restricted to anterior third.

Head and mesosoma dark amber orange, antennal scapes and legs brown, petiole and postpetiole dorsally infuscated, metasoma dark brown, almost black.

Queen measurements (n=1). HW 1.66, HL 1.42, EW 0.27, EL 0.37, ML 2.50, PeH 0.80, PNWdv 0.60, PPH 0.57.

Queen description. Head triangular, broader behind the eyes that in front, vertex straight sculpture entirely strigate over frontal and lateral surfaces except clypeus smooth, frontal clypeal margin very mildly concave. Mandibles strigate with a large apical and two smaller preapical teeth. When angled towards eye antennal scapes not surpassing dorsal eye margin.

Mesoscutum in profile evenly rounded from pronotum to scutellum, scutellum rounded and raise only slightly above surface of mesoscutum, surface smooth and shining except for pitted setal insertion points and lateral margins which are rugulose strigate. Pronotum and anterodorsal half of mesopleuron above central groove finely reticulate, posteroventral half strigulate. Propodeum with many raised ridges over entire surface, finely reticulate in between ridges. Petiole node triangular in profile, rectangular in posterior view with a straight dorsal margin, laterally with raised ridges that curve from junctures with propodeum and postpetiole towards dorsum, anterior and posterior surfaces with shallow alveolae. Metasomal tergites and sternites finely reticulate.

Distinctly bicoloured with head, legs and metasoma amber orange except area around ocelli infuscated and mesosoma light to dark brown.

Male Measurements (n=1). HW 1.46, HL 1.03, EW 0.33, EL 0.49, ML 2.36, PeH 0.62, PNWdv 0.60, PPH 0.53.

Male description. Head triangular with three ocelli. Eyes large, bulbous, oval in shape and positioned at an angle in lateral view such than longest axis point towards nearest lateral ocellus. Clypeus raised and rounded centrally, anterior margin straight. Mandibles with large apical tooth and two smaller teeth. When angled towards the eye antennal scapes, not surpassing dorsal eye margin. Sculpture coarsely rugose over entire surface, a few raised, transverse strigae present on clypeus and in between antennal insertion points.

Mesoscutum in profile evenly convex from anterior to posterior margin, sculpture coarsely alveolate-rugose tending towards rugulose-strigate anteriorly except for a narrow triangle that runs centrally from anterior margin to centre which is finely reticulate. Parapsidal lines present. Pronotum reticulate, rugose along dorsal margin. Scutellum large and bulbous with a central depression, sculpture alveolate-rugose. Mesopleuron finely reticulate with strigate overlay, reticulate only on anterior half above median groove. Propodeum finely reticulate, irregularly strigate on lateral surfaces only. Petiole and postpetiole with a flattened dorsal surface in lateral view, in dorsal view with a small median depression giving a slightly bilobed appearance, sculpture reticulate, strigate on posterior surface of petiole, petiole only slightly taller than postpetiole.

Metasomal tergites and sternites finely reticulate over entire surface.

Head and mesosoma dark reddish brown to dark brown, mandibles yellow, mandibular teeth amber. Metasoma dark reddish brown, posterior margins of tergites yellow. Head and mesosoma with large numbers of long, erect white setae except for central triangle on mesoscutum which is glabrous. Remained of specimen with hairs sloughed off.

Remarks. This species shows some clinal variation in size, sculpture and colour. Northern specimens collected close to the type locality are somewhat larger with coarser sculpture and with T1 entirely reticulate and more amber orange in colour. Those collected further south, around Alice Springs, are orange brown and most of the sculpture on T1 is very faint and restricted to the anterior third. Mitochondrial DNA indicates that all these samples are much more closely related to each other than to any other lineage so here they are considered a single species, although with additional evidence and samples these two morphotypes may prove to be distinct species.

Distribution. This species is known from the central desert region of the Northern Territory. Its range overlaps with M. eremoides sp. nov., M. eremum sp. nov. and M. subapterum .

COI sequences. Genbank accession numbers for this species are KC572889 –572892, KC572943 –572945 and KC572953 .

Additional material examined ( NTM, SAM, TERC). Northern Territory. Tennant Creek, J.F. Field; 73km E Devil's Marbles, -20.4755, 134.8331, 8 Jun 2009, K.S. Sparks, KSS83 ( SAM); 7 workers, Haasts Bluff Rd, - 23.4242, 132.0236, 13 Jun 2009, K.S. Sparks, KSS107; Davenport Ra., old policeman’s waterhole, -20.7528, 135.1852, 9 Jun 2009, K.S. Sparks, KSS85; KSS87; Telegraph Station, Alice Springs, -23.6693, 133.8835, 12 Dec 2010, A. Andersen, ANA11–10; ANA11–11; ANA11–13; ANA11–14; Alice Springs, -23.7 133.88, 10 Sep 1989, A.N. Andersen; Attack Creek, Central Australia, -18.3 134.5833, Nov 1995, B. Hoffmann; 300km N Alice Springs, -21.95 133.4666, 5 Nov 1998, A.N. Andersen; 130km W Uluru NP, Tjukaruru Rd, -25.46 129.35, 7 Sep 2009, A.L. Hertog; Davenport Ranges NP, Old Policemans Hut Waterhole, -20.753 135.1852, 30 May 2006, A. Hertog; Wycliffe Well, -20.84 134.24, 5 Nov 1998, A.N. Andersen; Soudan, -20.05 137.13, Nov 1996, A. Fisher.

Figures

FIGURE 5. Workers of the M. rothsteini (Forel) species complex in lateral, head and dorsal view of the mesosoma. Fig. 5 a – c: M. geminum, paratype (Litchfield NP, NT, ANA 10 – 22), d – f: M. hertogi, holotype (Lakefield NP, QLD, TERC 2), g – i: M. hoffmani, holotype (Mt Stanford Station, NT, TERC 70), j – l: M. humilior, (Alice Springs, NT, ANA 11 – 13), m – o: M. kidman, holotype (Top Springs, NT, TERC 71). Scale bars are 0.5 mm for all views.