Temnothorax subditivus

A relatively rare species that is found in open shrub and woodland habitats.

Identification
The worker of Temnothorax subditiva can be readily distinguished by the peculiarly shaped petiole, the peduncle of which is at least twice the length of the petiolar node; the rather uniform brownish color of most of the body; the obsolescent or missing thoracic sutures; the slender antennal scapes; and the sculpturing of the body. (Smith 1939)

Distribution
United States south to northern South America. Known from Texas, Mexico, Costa Rica and Colombia.

Distribution based on Regional Taxon Lists
Nearctic Region: United States. Neotropical Region: Costa Rica, Guatemala, Mexico, Venezuela.

Habitat
Shrub or open woodland habitats.

Abundance
Rarely collected.

USA - Texas
In New Braunfels workers were found walking on the leaves of bushes, in Walnut Creek on a dead limb lying on the ground. I did not succeed in finding the nest which is probably small and not very populous. Since the above was written I have succeeded in finding a single nest of T. subditiva. This was a small cell excavated in the bark of a huge willow (Salix nigra) near Austin. The cell contained about twenty workers and resembled in every way the nests of our corticolous species of Leptothorax. (Wheeler 1903)

I have taken this species nesting, like certain species of Temnothorax, in the bark of large trees (willows) at Austin, Del Valle, and New Braunfels, Texas, and have specimens taken by J. A. Mitchell at Victoria and by R. A. Vickery at Harlingen, in the same state. (Wheeler 1931)

Mexico - Nuevo Leon
In April 1991, two complete colonies of Temnothorax subditivus, including about 80 workers, numerous larvae and one single queen each, were collected in a mountainous wood region near Monterrey (Nuevo Leon, Mexico) at an elevation of ca. 1600 m in dry wood sticks at the ground. (Schumann 1992).

A number of workers, females and males were taken by Dr. Elisabeth Skwarra from several colonies at Mirador, Mexico. One of these was nesting in a thorn of Acacia cornigera, the others in the stems of a Melastomaceous shrub, Conostegia xalapensis. Females and workers from another colony taken at Tlacocintlo were nesting in a Tillandsia pruinosa. (Wheeler 1931)

Costa Rica
Temnothorax subditivus occurs in seasonally dry habitats. It inhabits scrubby vegetation and roadsides, nesting in small dead twigs or other dead plant cavities. Colonies are monogynous.

I have collected this species four times in Costa Rica, as follows:


 * Santa Rosa National Park, ridge between Playa Naranjo and Nancite: xeric scrub on rocky ridge; nest in dead branch; branch was dry and brittle.

Longino
 * Road from Pan American Highway to Monteverde, La Pita to Guacimal (below 500m elevation): three different collections from scrubby roadside vegetation, sweep samples and strays from tree trunks.

Columbia - Santa Marta
I..have collected the species in the Santa Marta region of Colombia. I found a small, monogynous colony under loose bark on a 2-3cm dia dead branch. The area of the nest was no more than 1x2cm. Crematogaster carinata were nesting throughout the same dead branch. Longino

Small dead twigs, on living living plants or on the ground, and in other (dead) plant cavities.

Morphology
Pupae of this caste have been found to bear some unusual appendages. Schumann (1992): "Two translucent lateral projections, having their origin at the basis of the third femurs, arch forward around the wing buds. Their length is about 0,4 mm. In addition, two blunt appendages, originating from the postpetiolar region, point forward, on both sides of the petiole. Below these projections, two short appendages on both sides of the petiole can be seen. Their length is about 0,15 mm (Fig. 2). The projections are translucent and filled with the pupal liquid. With higher magnification their surface appears roughly sculptured as the result of a partly thickened cuticle. Histological studies have revealed that there are no cellular structures detectable inside any of these appendages. They seem to be part of the pupal cuticle (Billen, pers. comm.)"

Nomenclature

 *  subditivus. Macromischa subditiva Wheeler, W.M. 1903b: 99, fig. 5 (w.) U.S.A. Wheeler, W.M. 1931b: 15 (q.); Smith, M.R. 1939e: 504 (m.). Combination in Leptothorax: Baroni Urbani, 1978b: 512; in Temnothorax: Bolton, 2003: 272. Senior synonym of flavitarsis, laevissima, luciliae: Baroni Urbani, 1978b: 512. See also: Creighton, 1966a: 282.
 * laevissima. Macromischa laevissima Wheeler, W.M. 1911h: 205 (w.) MEXICO. Junior synonym of subditivus: Baroni Urbani, 1978b: 512.
 * flavitarsis. Macromischa (Macromischa) flavitarsis Mann, 1920: 420 (w.q.) GUATEMALA. Wheeler, W.M. 1931b: 14 (m.). Junior synonym of subditivus: Baroni Urbani, 1978b: 512.
 * luciliae. Macromischa luciliae Mann, 1935, 35, fig. 1 (w.) GUATEMALA. Junior synonym of subditivus: Baroni Urbani, 1978b: 512.

Worker
Length 2-2.5 mm.

Head somewhat longer than broad, rounded at the posterior angles and convex above. Mandibles rather small, with three acute apical and three much smaller basal teeth. Clypeus short, broadly rounded in front, convex in the middle, with a prominent median carina running its full length and continued over the frontal area. Frontal area large, triangular, longer than broad. Antennae long, 12-jointed; scape extending beyond the posterior corner of the head to a distance equal to twice its breadth; first funicular joint nearly as long as the three succeeding joints together, joints 2-8 about as long as broad, two penultimate joints subequal, together as long as the terminal joint. Thorax short and thick-set, dorsum in profile convex, evenly rounded prothorax with broadly rounded angles, promesonotal suture very faintly, mesopinotal suture somewhat more distinctly indicated. Epinotum armed with two stout spines, which are very close together at their bases but diverge strongly outward, upward, and backward; epinotal declivity concave. Petiole long, with a conspicuously elongated peduncle which passes very abruptly into the transverse node; the latter is much compressed antero-posteriorly when seen in profile, the anterior and posterior surfaces being flattened and perpendicular, the summit of the node narrow and rounded when seen from behind, the edge of the node is horizontal and nearly straight. There is a small but distinct tooth on the ventral surface of the petiole near its anterior end. Postpetiole from above but little wider than the node of the petiole, fully twice as broad as long, rounded oblong; in profile it is nodiform, very convex dorsally, in both views showing a decided constriction at its insertion into the gaster. Gaster of the usual shape, with a long, powerful sting. Legs of the usual shape, with the femora conspicuously incrassated in the middle. There are no spurs on the middle and hind tibiae.

Head, including the mandibles and clypeus, subopaque, sharply longitudinally rugose; the rugae connected by subsidiary reticulate rugae on the base of the mandibles, cheeks, and sides of the head. Clypeus and frontal area more shining, the former with few rugae, especially near the middle. Thoracic dorsum shining, pleurae and epinoturn subopaque. Whole surface of thorax reticulate rugose, regularly in the opaque regions, more irregularly and more longitudinally on the shining dorsal surface. Petiole and postpetiole shining above, reticulate and subopaque on the ventral and lateral surfaces. Gaster very smooth and shining. Legs more opaque, finely but distinctly reticulate.

Head, thorax, and abdomen beset with sparse, erect, obtuse, silvery white hairs; antennae and legs with minute, appressed, pointed hairs of the same color.

Body black or, in immature specimens, very dark brown mandibles, antennae, legs and epinotal spines, tip of gaster, and sting yellow, scape and club of antennae, bases of epinotal spines, and greater portion of femora and tibiae infuscated.

Queen
(Wheeler 1931) 3.5 mm. Head subrectangular, as broad as long, broader behind than in front, with convex posterior border. Thorax less than twice as long as broad, mesonotum nearly as broad as long, flattened above; scutellum nearly as long as the epinotum, which is short, with sloping base and vertical declivity; spines acute, stout at base, shorter than their distance apart. Postpetiole nearly 2 1/2 times as broad as long; gaster large, elliptical, with concave anterior border. Pilosity and coloration as in the worker, head and thorax more opaque, evenly longitudinally rugulose.

Male
(Smith 1939) Length 2.2 mm.

Head, exclusive of mandibles, approximately as broad as long, with strongly convex posterior border, and moderately convex sides. Eye extremely large, convex, occupying at least half length of side of head, its anterior border almost touching base of mandible. Clypeus convex. Mandible small, toothed. Postocellar line longer than lateral ocellar line. Antenna slender, 13-segmented, the last 3 segments considerable enlarged. Thorax without Mayrian furrows, but with faint parapsidal furrows. Scutellum strongly gibbous. Epinotum without spines or tubercles. Wings pale, translucent, with very faint veins; discoidal, cubital, and radial cells lacking, but stigma well developed. Legs rather long and slender, femora not incrassate. In profile, peduncle of petiole noticeably short, its dorsal surface forming a gradually ascending slope, which meets the somewhat flattened posterior surface of the node to form a bluntly angular, but low node. Postpetiole from above transversely elliptical, wider than long, but not much wider than petiole. Gaster with basal angles.

Hairs grayish, short, erect, sparse; more abundant on gaster, especially toward apex. Pilosity sparse, appressed; most easily discernible on appendages.

Brown; appendages lighter; apices of coxae, trochanters, bases of femora, and tarsi even lighter.

Type Material
A rare species described from a few specimens taken along Walnut Creek, near Austin Texas (May 12, 1901), and at New Braunfels (June 3, 1901). Presumably in the MCZ and USNM.

References based on Global Ant Biodiversity Informatics

 * Baroni Urbani C. 1978. Materiali per una revisione dei Leptothorax neotropicali appartenenti al sottogenere Macromischa Roger, n. comb. (Hymenoptera: Formicidae). Entomol. Basil. 3: 395-618.
 * Brandao, C.R.F. 1991. Adendos ao catalogo abreviado das formigas da regiao neotropical (Hymenoptera: Formicidae). Rev. Bras. Entomol. 35: 319-412.
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 * Creighton W. S. 1966. The habits and distribution of Macromischa subditiva Wheeler (Hymenoptera: Formicidae). Psyche (Cambridge) 72:282-286.
 * Dattilo W. et al. 2019. MEXICO ANTS: incidence and abundance along the Nearctic-Neotropical interface. Ecology https://doi.org/10.1002/ecy.2944
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 * Kempf, W.W. 1972. Catalago abreviado das formigas da regiao Neotropical (Hym. Formicidae) Studia Entomologica 15(1-4).
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 * Maes, J.-M. and W.P. MacKay. 1993. Catalogo de las hormigas (Hymenoptera: Formicidae) de Nicaragua. Revista Nicaraguense de Entomologia 23.
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 * Rojas Fernandez P. 2010. Capítulo 24. Hormigas (Insecta: Hymenoptera: Formicidae). In: Diversidad Biológica de Veracruz. Volumen Invertebrados. CONABIO-Gobierno del Estado de Veracruz.
 * Vásquez-Bolaños M. 2011. Lista de especies de hormigas (Hymenoptera: Formicidae) para México. Dugesiana 18: 95-133
 * Wheeler W. M. 1931. New and little-known ants of the genera Macromischa, Creosomyrmex and Antillaemyrmex. Bulletin of the Museum of Comparative Zoology 72: 1-34.
 * Wheeler, G.C. and J. Wheeler. 1985. A checklist of Texas ants. Prairie Naturalist 17:49-64.