Myrmica pinetorum

A forest dweller associated with the eastern deciduous forest biome.

Identification
A member of the punctiventris group. Francoeur (2007) - M. pinetorum closely resembles Myrmica punctiventris but averages smaller in size, with larger frontal lobes, shorter scapes and spines, more delicate body sculpture. According to material examined, the presence of propodeal spines in males is observed in the northern part of the species range.

Key to punctiventris-group Myrmica species

Distribution
Eastern North America, from southern Canada south probably to the US Gulf states.

Distribution based on Regional Taxon Lists
Nearctic Region: United States.

Habitat
Coniferous, mixed and rather open deciduous woods, from dry to more humid conditions.

Biology
Based on collection data M. pinetorum inhabits not only coniferous forest, but also mixed and rather open deciduous woods, from dry to more humid conditions. In Pennsylvania I found this ant in a stand of Populus with Acer and Betula trees. Colonies are small and their nests in different types of soil: sandy, earthy or rocky, under denuded surface or under leaf litter, lichens, mosses and rocks. Dennis (1938) reported a nest in a cavity in dead wood. Wesson and Wesson (1940) observed carton turrets as nest entrances. (Francoeur 2007)

Nomenclature

 *  pinetorum. Myrmica punctiventris subsp. pinetorum Wheeler, W.M. 1905f: 384 (w.q.) U.S.A. Weber, 1950b: 217 (m.). Raised to species: Creighton, 1950a: 102. See also: Francoeur, 2007: 156.

Worker
Francoeur (2007) - Head in full face view subrectangular with convex sides; preoccipital (posterior) margin straight, corners largely rounded. Eyes convex and suboval, located slightly anteriorly of the mid point of the head sides. Anterior margin of clypeus angulo-convex; lateral wings thin and flat, with 1-3 short rugae. In dorsal view frontal lamellae laterally developed over the antennal articulation, triangular in shape with a rounded angle; posterior margin distinctly arrower and ending as a carinae merging width; in profile base evenly bent, dorsoventrally flattened with feeble dorsal concavity; in dorsal view shaft width regular along its axis. Funicular segments 3-5 as wide as long, remaining segments longer than broad; apical club of 4 segments.

Mesosoma, in profile, with mesometasternal external margin horizontally aligned, promesonotum very feebly convex, almost straight in larger specimens, distinctly higher than propodeum, both joining through an angle at the mesopropodeal furrow which remains shallow. In dorsal view promesonotum typically pear-like, posterior end of mesonotum narrower and anguloconvex. Strigil of protibia with a basal tooth; meso and metatibiae with delicate spurs, finely and pectinate on distal half. Propodeal lobes small, with a posterodorsal angle. Propodeal spines straight and acuminate, rather short and thin with a narrow base, shorter than the distance separating their tips, projecting backwards and upwards at 45°, usually parallel; sometimes a very feeble curve after the base. Petiole short, about as high as long but narrower; peduncle hidden by propodeal lobes; node seen in profile with anterior face slightly concave, forming a right angle with the dorsal surface which is rather flattened, followed by another angle with the concave posterior face, inclined down to the posterior margin. Postpetiole shorter than high and wide, height and width about equal; node profile typically with very short anterior and posterior vertical surfaces, united by a large convex one; sternal process strongly convex and globular, making 1/3 of the postpetiole height.

Mandibles striate with piligerous punctures. Frons and clypeus with parallel, acute and thin carinae, widely separated by subopaque, faintly microsculptured surface; reminder of head with reticulations. Mesosoma generally striatorugulose; rugulae thicker on pleurae and somewhat sinuous on promesonotum. Antennal fossae with parallel and convex carinae. Petiole and postpetiole rugose. Gaster smooth and shining; first segment with large round punctures. Long erect hairs moderately abundant on body; suberect on scapes. Gastric dorsum without distinct pubescence. General body color light to dark reddish brown; gaster darker; appendages lighter or more yellowish.

Queen
Francoeur (2007) - Basically similar to worker in shape of head, characters of sculpture, color and pilosity of body except the following. Head with three ocelli. Usual distinct mesosomal development of a queen and body size larger. Sculpture coarser on mesonotum, petiole and postpetiole. Mesopleurae with more delicate rugulae; transverse groove narrow and deeply impressed. Surface between spines smooth and shining; sometimes vestigial shagreening on lateral borders. Wings feebly tinted; submarginal cell of anterior wings partly subdivided posteriorly.

Male
Francoeur (2007) - Smaller than queen. In full face view head slightly longer than broad, narrower before eyes, with shallow elongated antennal fossae, posterior half evenly rounded. Mandibles elongate, blade subtriangular; masticatory margin with three apical teeth followed by 2-3 teeth or denticles. Clypeus convex, anterior margin angulate, finely lamellar mesially. Malar space short. Frontal triangle shallow and weakly delimited. Frontal lobes poorly developed, but distinct as thin carinae with straight lateral margins that diverge posteriorly, originating from toruli. Antennae 13-merous; scapes very short, shorter than or equal to combined length of next 2 segments; in profile scape base with a very faint dorsal flattening; length of second funicular segment equal to next two; funicular club of 5 segments. Eyes large and globular. Ocelli small, the antero-median 0.06-0.07 mm in diameter; distance between the posterior ocelli equal to 4-5 x diameter of anterior ocellus.

In lateral view, mesosoma rather long; mesonotum high. Mayrian furrows not impressed, weakened or absent posteriorly. Spurs of meso- and metatibia weakly pectinate. Metapleural lamellae small. Wings as in queen, but usually darker. Propodeum with two small, dentiform spines or two more or less developed protuberences marked by carinae, surface between them smooth and shining; spiracles round and well marked. In profile petiole rather short, with an anterior peduncle mostly hidden by propodeal lobes; ventral margin straight or very weakly concave with an anterior denticle; node with an anterior face concave, summit convex with longitudinal rugulae running to posterior margin. Postpetiole shorter than high and wide, about as large as wide; anterior and dorsal surfaces of dorsum forming a convex slope with summit ending posteriorly by a short declivity; sternum longer than high, ventral margin convex.

Head sculpture very fine, mainly shagreened; faint and short rugulae present on front and malar space, anastomosed on temples, surface punctulate. Mandibles faintly sculptured. Clypeus very faintly microsculptured, with or without short rugulae. Frontal triangle punctulate. Front with few rugulae, some reaching the ocellar triangle. Antenna with suberect to subdecumbent fine hairs longer than the width of segments, but shorter on funicular club. Pronotum densely shagreened; anterior and lateral areas of mesoscutum smooth and shining, Mayrian furrow as a thin line from which originate short rugulae, the medial ones longest. Meso- and metapleurae with parallel rugulae obliquely oriented; transverse grooves feebly impressed. Propodeal protuberences or spines with a row of fine erect hairs. Body pilosity moderately abundant, delicate, erect to decumbent. Lateral sides of petiole and postpetiole faintly sculptured, median area of dorsum smooth and shining. Gaster smooth and shining with some appressed hairs; first segment with large rounded, piliferous punctures. Body color black to blackish brown; appendages lighter.

Type Material
Francoeur (2007) - Lakehurst, New Jersey, USA; lectotype worker, here designated, in ; paralectotype workers and queens in,. M. punctiventris var. isfahani: Mt. Mitchell, Tyson, North Carolina, USA; lectotype worker, here designated, in ; paralectotype workers and queens in.

The syntype series (typus and cotypus) of Forel’s isfahani in includes specimens of both M. pinetorum and M. punctiventris collected by him on Mt. Mitchell, Tyson, North Carolina, at different altitudes, and also workers of M. punctiventris from Virginia. The workers and alate queens labeled as typus belong to M. pinetorum; all others are workers of M. punctiventris. The “typus” series is here selected as lectotype and paralectotypes, and this secures the synonymy of isfahani under M. pinetorum.