Stenamma exasperatum

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Stenamma exasperatum
Scientific classification
Kingdom: Animalia
Phylum: Arthropoda
Class: Insecta
Order: Hymenoptera
Family: Formicidae
Subfamily: Myrmicinae
Tribe: Stenammini
Genus: Stenamma
Species: S. exasperatum
Binomial name
Stenamma exasperatum
Snelling, R.R., 1973

Stenamma exasperatum casent0005814 profile 1.jpg

Stenamma exasperatum casent0005814 dorsal 1.jpg

Specimen labels

The type specimens were collected under a stone in a "Sequoia grove" (more likely a Sequoiadendron grove). Specimens have also been collected from litter samples and under a stone in a pine-fir forest.


Snelling (1973) - Eyes of worker with three facets in greatest diameter; first tergite densely and finely punctulate, with basal longitudinal striae and scattered coarse piligerous punctures; first sternite densely, finely punctulate; scapes and tibiae with ahundant fully erect hairs.

This species is most closely related to Stenamma heathi with which it shares details of clypeal structure and gastric sculpture. The sculpturation of the head and thorax are similar but in Stenamma exasperatum both are more clearly reticulate. The reticulae become less defined on the sides of the head and thorax of S. heathi, usually replaced by a series of irregular longitudinal rugulae. Although the hairs of the scapes and tibiae are fully erect in Stenamma exasperatum studied, there may be some variation not now evident. In Stenamma heathi these appendages usually have the hairs strongly decumbent, but in some specimens the hairs may be subdecumbent and with a few which are suberect. The hairs of the hind tibiae apparently are consistently decumbent in Stenamma heathi, fully erect in S. exasperatum. The erect hairs on the front of the head are conspicuously more abundant in Stenamma exasperatum and are more uniform in length. Some of the hairs on the front of the head of Stenamma heathi are three to four times the length of the shortest hairs and hairs of all lengths are sparser than in S. exasperatum.


Distribution based on Regional Taxon Lists

Nearctic Region: United States (type locality).

Distribution based on AntMaps


Distribution based on AntWeb specimens

Check data from AntWeb


USA. Known only from California.



The following information is derived from Barry Bolton's New General Catalogue, a catalogue of the world's ants.

  • exasperatum. Stenamma exasperatum Snelling, R.R. 1973c: 28, figs. 40, 41, 46, 47, 63 (w.) U.S.A.

Unless otherwise noted the text for the remainder of this section is reported from the publication that includes the original description.



Measurements. HL 0.87-0.93 (0.93); HW 0.70-0.77 (0.77); SL 0.60-0.66 (0.66); WL 1.00-1.13 (1.l3); PW 0.47-0.53 (0.53).

Head. A little longer than broad, CI 81-83 (82), longer than scape, a little narrowed toward occiput. Eyes small, with three facets in greatest diameter, OMD 2.16-2.33 (2.33) x EL; OI 10-11 (10). Scape stout, a little shorter than HW, SI 86-89 (87), distinctly thickened near apex. Mandible with longitudinal rugulae over most of length, shiny and sparsely punctate, cutting margin with six or seven teeth. Median lobe of clypeus not exceeding clypeal margin, longitudinally depressed and laterally carinulate, without transverse carinula. Clypeus and depressed frontal area shiny; frontal lobes roughened, slightly shiny; remainder of cephalic dorsum slightly shiny, finely punctulate, evenly and coarsely reticulo-rugose, with numerous coarse piligerous punctures.

Thorax. Pronotal neck slightly shiny, densely punctulate and with a few coarse punctures; laterally reticulo-rugose, interspaces punctate and slightly shiny; promesonotum regularly reticulo-rugose, interspaces shiny, with scattered obscure punctures. Mesopleura and sides of propodeum coarsely longitudinally rugose, inters paces closely punctate and slightly shiny. Metanotal depression broad and deep. Propodeum basally with a poorly defined transverse welt; basal face closely punctulate and with irregular rugulae tending to form reticulae; spines short, sharp, about two-thirds as long as distance between them; declivity closely punctulate and slightly shiny on upper half, lower half shiny and impunctate.

Petiole. Dorsal face of anterior peduncle about as long as anterior face of node; summit of node narrowly rounded, anterior and posterior faces about equal; peduncle without ventral tooth anteriorly. Postpetiole, from above, about as broad as long, sides slightly convex. Sides and venter of petiole and postpetiole dull, densely punctulate; nodes sharply reticulo-rugose and dull, with closely punctulate interspaces.

Gaster. First tergite densely punctulate and dull on basal half, or more; entire segment with numerous coarse, piligerous punctures; punctulate area with numerous fine longitudinal rugulae, forming reticulae toward base. First sternite similar, but striatopunctulate on basal half, rugulae less conspicuous. Remainder of gaster as usual in genus.

Pilosity. Scapes, femora and tibiae with abundant fully erect whitish hairs of even length; cephalic and thoracic dorsa with numerous evenly spaced fully erect hairs of uniform length. Gastric hairs a little denser than in S. heathi.

Color. Yellowish ferruginous, median flagellar segments a little darker; mandibular margins darker; antennal club and tibiae yellowish.

Type Material

Holotype and three paratype workers: all specimens in Los Angeles County Museum of Natural History. Calaveras Big Trees, Calaveras Co., California. June 1952. R. R. Snelling, under stone in Sequoia grove.


Descriptive. Exasperatum, L., so named to express my feeling upon discovering that these specimens, thought to be Stenamma heathi, represent still another species.


  • Snelling, R. R. 1973c. Studies on California ants. 7. The genus Stenamma (Hymenoptera: Formicidae). Contr. Sci. (Los Angel.) 245: 1-38 (page 28, figs. 40, 41, 46, 47, 63 worker described)