Diagnostic description.

Female. Body size (10.0–11.5) mm, ovipositor length (15.0–16.0) mm, fore wing length (8.3–8.7) mm (Fig. 69); colouration black, fore and mid legs excluding coxa orange, tarsomeres cream-coloured, hind tasomere cream-coloured execpt basal two-thirds of tarsomere one and tarsomere five an dclaw dark brown, ovipositor sheath dark brown; wings hyaline except for indistinct brown infuscation at apex 1st marginal and 4th submarginal cell (Fig. 70G), hind wing veins spectral; head shape quadrate, width (1.1–1.5) × length, postocular space (0.5) × eye length in dorsal view (Fig. 70C), raised transverse carina above toruli absent, malar space (0.2) × height of eye (Fig. 70A); length of scape (1.5–1.8) × length of pedicel, 1st flagellomere (1.3–1.5) × length of scape, (0.5–0.7) × 2nd flagellomere; mesosoma length (1.7–1.8) × height; mesoscutum in lateral view rounded antero-dorsally (Fig. 70D); mesoscutum length (0.9–1.1) × width in dorsal view (Fig. 70E); medial lobe coarse transverse carinae; ovipositor guide transverse, positioned medial (Fig. 70F); ovipositor sheath length (1.7–1.8) × fore wing length (Fig. 69); 2-Rs+M (0.5–0.6) × 1-Rs+M, three hamuli, basal hamulus separated from other two (Fig. 70G); metasoma clavate, T1+T2 length (3.4) × width in dorsal view.

Abacus planiceps is similar to A. albimanus but can be separated based on black metafemur colouration (reddish-brown in A. albimanus), dark brown ovipositor sheath (large cream-coloured band sub-apically in A. albimanus), coarser transverse striations on mesoscutum (finer striations in A. albimanus).