Stenamma Westwood

Branstetter, Michael G., 2009, The ant genus Stenamma Westwood (Hymenoptera: Formicidae) redefined, with a description of a new genus Propodilobus, Zootaxa 2221, pp. 41-57 : 42-43

Stenamma Westwood

Stenamma Westwood, 1839: 219 . Type-species: Stenamma westwoodii , by monotypy.

Asemorhoptrum Mayr, 1861: 76 . Type-species: Myrmica lippula , by monotypy. [Synonymy with Stenamma by André, 1883: 310.]

Theryella Santschi, 1921: 68 . Type-species: Theryella myops (provisional junior synonym of Stenamma punctiventre ), by monotypy. [Synonymy with Stenamma by Santschi, 1923: 136.]

Diagnosis of Stenamma . A new diagnosis of the Stenamma worker caste is presented followed by a short discussion on interspecific variation and how to distinguish Stenamma from closely related genera. The classification of Bolton (2003) placed Stenamma within the tribe Stenammini , which, as currently defined, is not monophyletic ( Brady et al. 2006; Moreau et al. 2006). Stenamma instead is more closely related to the genera Aphaenogaster Mayr and Messor Forel , suggesting that the older tribal classification of Emery (1921), which included these genera together, should be reconsidered. Some of the characters mentioned here may help to diagnose the group formed by Stenamma , Aphaenogaster , and Messor . Standard images of Stenamma representing species from different biogeographic regions are shown in Figures 2–16 .

Diagnosis of the Stenamma worker caste. With characters of the Myrmicinae as described by Bolton (2003), and the following more specific features:

1. Mandible triangular to elongate triangular; masticatory margin usually with 6–8 teeth or denticles (rarely 9 or 10) which decrease in size irregularly from apex to base; teeth on basal half frequently reduced and poorly defined.

2. Palp formula 4,3.

3. Apex of anterior clypeal margin with a small to prominent notch or concavity, never smoothly convex or with a projecting tooth.

4. Anterior clypeal margin usually lacking a strong isolated median seta.

5. Median portion of clypeus often longitudinally bicarinate and with area between carinae slightly to strongly depressed.

6. Posteromedial margin of clypeus narrowed and prolonged backward between frontal lobes; width not exceeding that of frontal lobes in full-face view.

7. Frontal lobes small and closely approximated, not entirely covering antennal insertions.

8. Antennal scrobes and frontal carinae absent.

9. Torular lobe present and visible in full-face view projecting over condylar bulb.

10. Compound eyes located slightly to distinctly in front of midlength of side of head (excluding mandibles), small to moderate in size, usually with 2–12 ommatidia across greatest diameter.

11. Antenna 12 segmented and terminating in a distinct to indistinct 4-segmented club (ACI 60-70).

12. Posteroventral corners of head lacking grooves.

13. Promesonotum convex in profile, often low domed-convex and very prominent; faint impression or line marking track of former promesonotal suture sometimes present dorsally.

14. Metanotal groove present.

15. Propodeum usually armed with a pair of teeth or short spines (rarely unarmed or with long spines).

16. Propodeal lobes present and prominent, rounded to quadrate in shape, never long and projecting dorsally.

17. Middle and hind tibiae lacking spurs.

18. Pretarsal claws small, simple.

19. Petiole with a long, anterior peduncle and sometimes with an anteroventral process.

20. Postpetiole with short peduncle and low node often slightly longer than broad, never distinctively broader than long.

21. Postpetiolar node always wider than petiolar node.

22. Basigastral striae often present on anterior margin of abdominal tergite 4.

23. Metasternal process present and often well developed.

Figures

FIGURES 2 – 16. Full-face, profile, and dorsal images of several Stenamma species, representing the Palearctic, Nearctic, and Neotropical regions. Figures 2 – 4: S. debile CASENT 0605171 (Bavaria, Germany). Figures 4 – 6: S. nipponense CASENT 0605172 (Hokkaido, Japan). Figures 8 – 9: S. dyscheres CASENT 0171182 (CA, USA). Figures 11 – 13: S. expolitum CASENT 0600043 (Heredia Prov., Costa Rica). Figures 14 – 16: S. diversum CASENT 0605173 (Izabal, Guatemala).