Secostruma

A monotypic genus known from a single worker of Secostruma lethifera. This holotype was collected "from a soil-core sample taken on the forested slopes of Gunong Silam, Sabah."

Identification
Bolton (1988) - Autapomorphies isolating this genus include the unique structure of the mandibles and the construction of the gaster which are not duplicated elsewhere in the Myrmicinae. The combination of characters given in the diagnosis of the genus immediately isolates Secostruma from all other known myrmicine ants.

Biology
The biology of the single species of this genus was speculated upon by Bolton (see the biology section of Secostruma lethifera).

Castes
Known only from the worker caste.

Nomenclature

 *  SECOSTRUMA [Myrmicinae: Myrmicini]
 * Secostruma Bolton, 1988c: 264. Type-species: Secostruma lethifera, by original designation.

DIAGNOSIS OF WORKER. Subterranean ants belonging to the subfamily Myrmicinae, with the following combination of characters.

1. Palp formula 4,3 (in situ count); right maxillary palp broken.

2. Masticatory margin of mandible with a stout curved acute apical tooth, subtended by a long edentate section of the margin. Basad of the edentate section the margin with a row of 4 small teeth. Edentate section of margin longer than tooth-bearing section.

3. Median clypeal seta absent. Median indentation of anterior clypeal margin with a seta on each side, these setae directed anteromedially and their apices crossing over.

4. Lateral portions of clypeus raised into sharp narrow ridges or shield-walls in front of the antennal insertions.

5. Median portion of clypeus posteriorly broadly inserted between wide strongly developed frontal lobes. Anterior quarter of median portion of clypeus suddenly angled downwards to the margin; the latter indented medially.

6. Frontal triangle depressed and sharply demarcated.

7. Areas of antennal articulations deep, bounded externally by a carina on each side which curves anteriorly from the hind end of the frontal lobe and is confluent with the narrow raised portion of the clypeal margin.

8. Antennae with 12 segments, the three apical segments forming a strong club.

9. Antennal scape with a right-angled bend near the base, the portion proximal to the bend expanded and concealing the scape articulation. Articulatory stem and condylar bulb projecting into antennal socket at roughly a right-angle from the downbent basal section of the scape.

10. Frontal carinae and antennal scrobes absent.

11. Eyes vestigial, marked only by an irregular spot at the approximate midlength of the side of the head.

12. Alitrunk compact, promesonotum convex in profile, propodeum humped in profile and with a pair of short spines.

13. Metapleurallobes very large and broadly rounded, connected to the propodeal spines by short lamellae.

14. Propodeal spiracle very low on side of sclerite, at junction with metapleuron and close to the margin of the declivity.

15. Ventral alitrunk with a long narrow V-shaped open cleft running from the posterior margin forwards between the hind coxal cavities. (Presence of metasternal process cannot be confirmed because of position of coxae.)

16. Simple tibial spurs present on middle and hind legs.

17. Petiole in profile or in dorsal view elongate and subcylindrical, with a short broad anterior peduncle and lacking a developed node.

18. Entirety of gastral dorsum formed by the much-expanded first tergite; this curves strongly downwards posteriorly so that tergites 2-4 are on what is functionally the ventral surface of the gaster. Anal and sting orifices mid-ventral in profile view of gaster.

19. Cuticle thick and strong, armoured and strongly sculpted.