Strumigenys rostrata

Identification
Bolton (2000) - Of the seven species in the group Strumigenys chiricahua and Strumigenys hyalina are immediately separated as they are the only ones to have a mandibular diastema that is decidedly longer than the basal tooth. Strumigenys californica is isolated by the presence of distinctly sculptured zones at the apices of the first gastral tergite and sternite, these zones remaining smooth and polished in all other species. In the relatively large rostrata (HL 0.61-0.72, HW 0.42-0.47) the dentition is coarse, with teeth 6 and 7 enlarged (see above), and its specialised projecting pilosity is characteristic: stout simple hairs are present in apicoscrobal position, at pronotal humerus and on mesonotum (one pair). The remaining three species, Strumigenys arizonica, Strumigenys bunki, Strumigenys carolinensis, average smaller (HL 0.54-0.64, HW 0.37-0.41) and have much smaller finer dentition (in particular teeth 6 and 7 are insignificant), nor do they have pilosity like rostrata at all the points mentioned; in particular all three lack an apicoscrobal hair. S. carolinensis has a pair of long flagellate hairs on the mesonotum, not developed in arizonica and bunki where mesonotal hairs are simple or absent. These last two species separate on relative development of spongiform tissue (see key) and on the complete lack of mesonotal standing hairs but presence of long fine gastral pilosity in bunki. Compared to this arizonica has a single pair of short simple erect hairs on the mesonotum and the first gastral tergite is sparsely clothed with very short stubbly simple hairs.

Flagellate hairs that project from the dorsal (outer) surface of the hind basitarsus are absent in rostrata and arizonica, always present in carolinensis. In bunki some specimens show such hairs, others do not. Because most bunki I have seen have been badly treated and poorly mounted I suspect that these fine and delicate hairs have been mostly stripped away and that they will always be present in fresh material.

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



Nomenclature

 *  rostrata. Strumigenys rostrata Emery, 1895c: 329, pl. 8, figs. 23, 24 (w.q.m.) U.S.A. Wheeler, G.C. & Wheeler, J. 1955a: 144 (l.). Combination in S. (Cephaloxys): Emery, 1924d: 325; in S. (Trichoscapa): Smith, M.R., 1943f: 307; Creighton, 1950a: 309; in Smithistruma: Smith, M.R., 1951a: 828; Brown, 1953g: 84; in Pyramica: Bolton, 1999: 1673; in Strumigenys: Baroni Urbani & De Andrade, 2007: 127. See also: Wilson, 1954: 485; Bolton, 2000: 129.

Worker
TL 2.4-2.8, HL 0.61-0.72, HW 0.42-0.47, CI 66-68, ML 0.10-0.14, MI 17-20, SL 0.28-0.32, SI 67-72, PW 0.28-0.32, AL 0.61-0.69 (30 measured; incorporating maximum and minimum dimensions of Brown, 1953a). Basal lamella longer than any of the teeth, feebly recurved; without a diastema between lamella and basal tooth. Teeth 1-5 strongly developed, coarse and conical; teeth 3 and 5 are longer than 4; tooth 3 is longest on the margin but only slightly more so than tooth 5. Teeth 6-7 also strongly developed and conical, shorter than 1-5 but not much shorter than 4, so that in full-face view the entire visible margin has a coarsely 7-dentate appearance. Anterior clypeal margin extremely shallowly concave. Eye with 4-5 ommatidia in the longest row. Basigastral costulae numerous and sharply defined, extending about one-quarter the length of the tergite. Apicoscrobal hair fairly stout and curved, blunt or truncated apically. Cephalic dorsum with 4 curved suberect hairs close to occipital margin. Pronotal humeral hair stout, straight or only very shallowly curved; a single similar pair on the mesonotum. First gastral tergite with standing filiform hairs arranged in a basal and an apical transverse row; tergite between these rows usually without standing pilosity, rarely with a few hairs present. Dorsal (outer) surfaces of middle and hind basitarsi without projecting long fine flagellate hairs.

Type Material
Syntype workers, queens and male, U.S.A. District of Columbia, Washington (Pergande) [examined].