Propodilobus

A monotypic genus that is only known from workers of Propodilobus pingorum. Specimens have been collected as part of a soil core in mixed dipterocarp forest, in Berlese Funnel extractions of leaf mold and from winkler sampling of leaf litter. Beyond these collection records, nothing is known about the biology of these ants.

Identification
Branstetter (2009) - Propodilobus can be distinguished from Stenamma by the reduced palp formula (3,2 versus 4,3), smoothly convex anterior clypeal margin, distinct 3-segmented antennal club (ACI 74-75 versus 60-70), and elongate propodeal lobes. In addition, the postpetiole is broader than long and the scape and funiculus of Propodilobus have a more robust appearance than in Stenamma.

Propodilobus may be confused with Lordomyrma since Lordomyrma is morphologically diverse and currently lacks an adequate diagnosis. It is possible that when a more comprehensive morphological review of Lordomyrma is undertaken or the phylogenetic position of Propodilobus is tested with molecular data, Propodilobus will be synonymized under Lordomyrma or a related genus. Despite this, from the diagnoses listed in Sarnat (2006) and Taylor (2009), Propodilobus can be distinguished from Lordomyrma by its lack of longitudinal carinae on the clypeus, lack of scrobes and frontal carinae, the presence of an elongate petiolar peduncle, and the presence of elongate propodeal lobes.

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

1. Mandibles elongate triangular with 6 teeth which decrease in size irregularly from apex to base; teeth on basal half reduced and poorly defined.

2. Palp formula 3,2.

3. Apex of anterior clypeal margin smoothly convex.

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

5. Median portion of clypeus lacking longitudinal carinae.

6. Posteromedial margin of clypeus narrowed and prolonged backward between frontal lobes.

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

8. Antennal scrobes and frontal carinae absent.

9. Antenna 12 segmented and terminating in a distinct 3-segmented club (ACI 74-75).

10. Promesonotum convex and prominent in profile.

11. Metanotal groove present.

12. Propodeum armed with a pair of well-developed spines.

13. Propodeal lobes present and elongate, bluntly triangular in shape and directed posterodorsally; space between lobes and propodeal spines distinctly U-shaped.

14. Middle and hind tibiae lacking spurs.

15. Pretarsal claws small, simple.

16. Petiole with a long, anterior peduncle; anteroventral process lacking.

17. Postpetiole broader than long.

Distribution
Borneo (Sarawak, Malaysia)

Castes
Known only from the worker caste.

Nomenclature

 *  PROPODILOBUS [Myrmicinae: incertae sedis in Stenammini]
 * Propodilobus Branstetter, 2009: 54. Type-species: Stenamma orientale (junior homonym, replaced by Stenamma pingorum), by original designation.

Etymology
The name is descriptive of the prominent propodeal lobes found on the type specimen. It is a combination of propodeum, which is the first abdominal segment in apocritan Hymenoptera, and lobus, L., meaning lobe.