Stigmomyrmex rugulosus

Known from a few worker specimens.

Identification
Radchenko and Dlussky (2017) - By the main diagnostic features S. rugulosus resembles Stigmomyrmex venustus, but well differs from it by the sculpture of the head, mesosoma and waist, which have a not coarse, almost straight longitudinal rugulosity, and the foveolate sculpture is well developed only on the head dorsum and on the mesonotal dorsum between rugulae. Also there are numerous suberect to subdecumbent hairs on its legs. Whereas, the whole head, mesosoma and waist of S. venustus have only foveolate sculpture and its legs are hairless.

Distribution
This taxon was described from Baltic Amber (Eocene) and Bitterfeld Amber (Eocene).

Castes
Only known from workers.

Nomenclature

 * † rugulosus. †Stigmomyrmex rugulosus Radchenko & Dlussky, 2017: 775, figs. 2-3 (w.) BALTIC AMBER (Eocene).

Description
Holotype: HL 0.56, OL 0.15, ML 0.72, PL 0.19, PPL 0.16, PPH 0.16, ESL 0.11, total length 2.67 mm; paratype worker: HL 0.55, SL 0.27, OL 0.15, ML 0.73, PL 0.20, PH 0.17, PPL 0.16, PPH 0.16, HTL 0.31, ESL 0.10, total length 2.55 mm. Ratios. Holotype worker: OL/HL 0.26, PL/HL 0.33; ESL/HL 0.19; paratype worker: SL/HL 0.49, OL/HL 0.27, PL/HL 0.36, PL/PH 1.18, PPL/HL 0.29, PPL/PPH 1.00, ESL/HL 0.18.

Total length ca. 2.6–2.7 mm. Head elongate, eyes of moderate size, situated distinctly in front of midlength of sides of head, length of genae subequal to maximum diameter of eye. Antennae 10-segmented, with distinct 3-segmented club; scape short, far not reaching occipital margin. Clypeus and mandibles obscured in the specimens.

Mesosoma of moderate length, narrowed posteriorly, promesonotal suture vestigial, but visible, metanotal groove distinct, quite deep. Pronotum with distinctly angulated and pointed humeri (seen from above). Propodeum with rather short teeth, length of dorsal surface of propodeum subequal to posterior one. Petiole subsessile, short, postpetiole wider than long and wider than petiole. Middle and hind tibiae without spurs.

Head dorsum with longitudinal straight rugulae and dense foveolate sculpture between them. Mesosoma and waist longitudinally rugulose, only mesonotal dorsum additionally with foveae.

Body with abundant, long, straight erect to suberect hairs. Outer surface of scape and legs with similar hairs.

Type Material
Holotype worker, Baltic amber, Late Eocene, No. MIBUG 1995 (WK 1643); paratype worker, Bitterfeld amber, Late Eocene, No. 14/201 (MfN).

Etymology
The name derived from the rugulose sculpture on the head, mesosoma and waist.