Monomorium laeve

Heterick (2001) - Monomorium laeve is abundant throughout Australia, but is found less frequently than Monomorium fieldi and Monomorium sydneyense in urban settings. However, the ant does enter dwellings, particularly in rural areas. The label on one pin holding three specimens collected at Mt Stromlo, in the Australian Capital Territory, states that they were “infesting quarters”. In its natural environment this ant feeds on animal food and on seeds (Clark 1924).

Identification
Heterick (2001) - A member of the monomorium group. The workers can be distinguished from the very similar Monomorium disetigerum workers by the presence of long setae on the occiput and propodeum, and more than one pair of erect setae on the promesonotum, and from Monomorium anderseni workers by the narrower nodes. Despite variability in overall size and minor allometric differences between large and small specimens. The smallest specimens have small compact eyes, compared with somewhat elongate, coarsely faceted eyes in larger workers, but these are simply extremes on a continuum: intermediate sized workers exhibit intermediate eye size and morphology.

Heterick (2009) - A yellow ant whose workers range in appearance from very small and compact (mainly northern Australia) with small, oval eyes to small- medium and gracile with large, rather elongate eyes (mainly the wetter south-west). Many workers with intermediate features connect the two extremes.

Distribution based on Regional Taxon Lists
Australasian Region: Australia.

Nomenclature

 *  laeve. Monomorium laeve Mayr, 1876: 101 (w.) AUSTRALIA. Heterick, 2001: 404 (q.m.). Combination in M. (Mitara): Emery, 1913b: 261; in M. (Lampromyrmex): Emery, 1922e: 184. Senior synonym of broomense, ilia, lamingtonensis: Heterick, 2001: 404.
 * ilia. Monomorium (Martia) ilia Forel, 1907h: 277 (w.q.) AUSTRALIA. Forel, 1910b: 30 (q.); Wheeler, G.C. & Wheeler, J. 1973a: 30 (l.). Combination in M. (Lampromyrmex): Emery, 1922e: 184. Junior synonym of laeve: Heterick, 2001: 404.
 * broomense. Monomorium (Mitara) laeve r. broomense Forel, 1915b: 74 (w.) AUSTRALIA. Raised to species: Taylor & Brown, D.R. 1985: 70. Junior synonym of laeve: Heterick, 2001: 404.
 * lamingtonensis. Monomorium (Mitara) ilia var. lamingtonensis Forel, 1915b: 73 (w.q.) AUSTRALIA. Combination in M. (Lampromyrmex): Emery, 1922e: 184. Subspecies of ilium: Taylor & Brown, D.R. 1985: 71. Junior synonym of laeve: Heterick, 2001: 404.

Worker
Heterick (2001) - HML 0.98-1.48; HL 0.40-0.59; HW 0.31-0.48; Cel 72-82; SL 0.27-0.43; SI 86-100; PW 0.18--0.26 (25 measured).

As for the worker of Monomorium fieldi, but with the following apomorphies.

Head. Eye moderate, eye width 0.5-1.5 x greatest width of antennal scape to large, eye width greater than 1.5x greatest width of antennal scape. Frontal lobes parallel, sinuate. Venter of head capsule without elongate, basket-shaped setae.

Alitrunk. Promesonotal sculpture absent, promesonotum smooth and shining, or present in form of microreticulation on and around katepisternum, otherwise promesonotum smooth and shining. Propodeum smooth and shining; dorsal propodeal face gently convex; lobes present as blunt flanges. Declivitous face of propodeum smoothly convex. Propodeal setulae absent. Propodeal spiracle lateral and about midway between metanotal groove and declivitous face of propodeum.

Petiole and postpetiole. Petiolar node conical, dorsally rounded; sculpture absent, petiolar node smooth and shining. Ventral lobe present in some individuals. Height ratio of petiole to postpetiole near 4:3; height-length ratio of postpetiole near 2:1.

General characters. Colour various shades of yellow. Worker caste monomorphic.

Queen
Heterick (2001) - HML 1.89-2.85; HL 0.53-0.83; HW 0.48-0.69; Cel 80-93; SL 0.41-0.62; SI 79-96; PW 0.34-0.64 (19 measured).

As for the queen of Monomorium fieldi, but with the following apomorphies.

Head. Head square or rectangular; vertex planar, or convex; frons striolate between frontal carinae, otherwise smooth and shining with a combination of decumbent and subdecumbent setulae and erect and suberect setae, or striolate with a combination of appressed setulae and erect and suberect setae. Compound eyes ovoid; (viewed from front) compound eyes set in anterior half of head capsule; (viewed laterally) compound eyes set posterior of the midline of head capsule, or set at midline of head.

Alitrunk. Mesoscutal pilosity consisting of numerous incurved erect and suberect setae; length-width ratio of mesoscutum and scutellum combined near 2:1. Dorsal propodeal face sloping posteriad, with wedge-shaped flattening or shallow depression that is widest between propodeal angles. Propodeal lobes absent or indistinct, or present as blunt flanges. Propodeal setulae appressed, or decumbent and subdecumbent. Propodeal spiracle lateral and nearer metanotal groove than declivitous face of propodeum.

Petiole and postpetiole. Petiolar node cuboidal, or cuneate, dorsally rounded, or tumular; sculpture absent, petiolar node smooth and shining, or present in form of microreticulation. Ratio of greatest node breadth (viewed from front) to greatest node width (viewed in profile) near 2:1 to near 1:1. Anteroventral process always absent or vestigial. Height-length ratio of postpetiole near 3:1 to near 2:1. Sculpture absent on dorsum, at least: postpetiole smooth and shining, or present in form of microreticulation; ventral process present and distinct.

General characters. Colour tawny yellow-orange to orange, often with some darker infuscation of mesonotum and gastral tergites. Brachypterous alates seen and examined. Ergatoid or worker-female intercastes not seen.

Male
Heterick (2001) - HML 2.00-2.61; HL 0.55-0.67; HW 0.61-0.75; Cei 104-115; SL 0.17-0.21; SI 26-31; PW 0.80-0.90 (7 measured).

As for the male of Monomorium fieldi, but with the following apomorphies.

Head. Head width-mesoscutal width ratio near 1:1 to near 3:4. Maximum number of mandibular teeth and denticles: four.

Alitrunk. Dorsal appearance of mesoscutum smooth and shining; mesoscutal pilosity consisting of long, dense setae. Axillae separated by distance of about half greatest width of scutellum.

Petiole and postpetiole. Sculpture absent, petiolar node smooth and shining; ratio of greatest node breadth (viewed from front) to greatest node width (viewed in profile) near 3:4. Anteroventral process always absent or vestigial. Ventral process of postpetiole present and distinct.

Gaster. Pilosity of first gastral tergite consisting of combination of appressed setulae and longer, erect and suberect setae.

General characters. Colour of head dark chocolate, legs depigmented straw yellow.