Myrmica striolagaster

This species nests under stones. Brood was present in nests in June in New Mexico and one nest was under a stone together with Camponotus vicinus (Mackay & Mackay, 2002). It has been found in Pinyon pine, ponderosa pine, cedar and oak wood lands (silver leaf, white oak), sycamore canyons and grasslands in forests. It is one of the few Myrmica species which nests in dry habitats. It is also the host for the inquiline Myrmica colax.

Identification
The workers of this species are easily recognized by the longitudinal striations at the base of the gaster and by longitudinally striate antennal scapes. The striations on the gaster are occasionally fine, and difficult to see, in which case the large punctures are generally obvious. (Mackay & Mackay, 2002).

Cole (1953) - This species is very distinctive, readily recognized, and in several respects wholly different from other known species and subspecies of Myrmica. In its gastric punctation the new species is somewhat similar to the members of the punctiventris group. But the new species is very much different from Myrmica pinetorum and Myrmica punctiventris of eastern and midwestern distribution. The gastric punctures are more numerous, coarser, and more extensive than those of the punctiventris group and they are accompanied basally by numerous, fine, longitudinal striae which are absent from the former. Other very distinctive features of the new species are the extremely coarse, rugo-reticulate sculpturing of the body, the abundant and coarse pilosity, and the laminate antennal scapes, none of which is characteristic of the punctiventris group.

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

Biology
This ant is the host for the rare Myrmica colax, found only once in Limpia Canyon, Davis Mountains, Texas.

Nomenclature

 *  striolagaster. Myrmica striolagaster Cole, 1953a: 81 (w.) U.S.A. Cole, 1957c: 208 (q.m.); Wheeler, G.C. & Wheeler, J. 1972b: 234 (l.).

Description
Holotype, worker (Cole Coll. No. N-116). Overall length, 6.14 mm.; alitrunk, 1.82 mm.; petiole and postpetiole combined, 0.95 mm.

Head, excluding mandibles, as long as broad (1.10 mm.) between the eyes, the sides moderately convex, the occipital border nearly straight, and the corners rounded. Frontal carinae broad, thin, directed upward, and with rounded apical border. Antennal scape with a right angle bend near the base and a shallow crescentic lamina at the bend. Labial palpi 3-segmented; maxillary palpi 6-segmented.

Thorax with its dorsal surface feebly convex when viewed in profile and with a rather broad and distinct mesoepinotal suture. Epinotal spines robust, pointed, nearly straight, deflected upward, outward, and backward, about as long as the distance between their bases. Petiole with a feebly concave anterior face and a convex dorsal surface, a little higher than the distance from the tip of the ventral tooth to the postpetiole. Postpetiole higher than long, higher than the petiole, submoniliform when viewed from above.

Head, alitrunk, petiole, and postpetiole coarsely rugo-reticulate. Antennal scapes and mandibles coarsely and longitudinally striate. Clypeus longitudinally and coarsely carinate. First gastric segment densely and coarsely punctate basally and with numerous, fine, longitudinal, basal striae. Pilosity of entire body coarse and very dense, the hairs golden, rather long, somewhat blunt, and quite uniform in length. Head, alitrunk, petiole, and postpetiole subopaque; gaster shining except at the striolate base of the first segment.

Color of head and alitrunk dark ferrugineous; petiole, postpetiole, and gaster darker.

Variation in the paratype series: In the series of 69 paratype workers the overall length varies from 5.57 to 6.50 mm. Most characteristics seem to be remarkably uniform. Color variation is only relatively slight as is that of pilosity and sculpture.