Diacamma Mayr, 1862

Diacamma Mayr, 1862 View in CoL

( Figs 3B View Fig , 5B View Fig , 7B View Fig )

Recognition of gamergate (mated and egg-laying worker). Morphological queen absent; lacking wings; large ants measuring ca. 10 mm; head, mesosoma and petiole covered with deep rugae; petiole massive, with pair of spines on posterodorsal portion.

Description of gamergate. Winged queens are not known in this genus; the physically same females can become either the worker or functional queen (gamergate) depending on social circumstances (if newly emerged females lost gemmae just after emergence from cocoons, then they become workers) (see FUKUMOTO et al. 1989, PEETERS & HIGASHI 1989). Large ants, with total body length ca. 10 mm in the Japanese species. Head, mesosoma and petiole covered with deep rugae. Head longer than broad, with weakly convex posterior margin, parallel lateral margins and broadly rounded posterolateral corners; occipital carina developed. Clypeus distinctly protruding anteriad and tapering apically. Eye large with ca. 40 ommatidia along its longest axis, essentially without standing hairs; with head in full-face view eye distinctly breaking lateral margin of head. Mandible elongate-triangular, with small teeth along its masticatory margin; teeth on basal 1/3 of masticatory margin very small; basal pit absent. With mesosoma in dorsal view, promesonotum distinctly narrower than head; promesonotal suture distinct; metanotal groove absent. With mesosoma in lateral view, deep pit (gemmal pit) present just above mesopleuron; mesopleuron not divided into upper and lower sections. Lateral face of propodeum separated from metapleuron by indistinct line; propodeal spiracle elevated from level of cuticle; its opening linear. Petiole massive, with pair of spines on posterodorsal portion; subpetiolar process developed, in profile view concave medially to form anterior and posterior spines, without anterior fenestra. Prora rather conspicuous, directed anteriad. Gastral constriction strong; pretergite and presternite of gastral segment II generally more or less exposed in mounted specimens, densely with fine transverse striation; cinctus ‘narrow’ zone with cross-ribs. Both mid- and hindtibiae with simple spur and longer pectinate spur.

Caste differences. Morphologically the normal worker and gamergate worker are identical except for presence/ absence of gemmae, but behaviorally different.

Remarks. The Japanese species is very similar to the Indian species Diacamma indicum , but its status is not yet settled. According to OGATA (1987) the male hindwing has a jugal lobe.