Small terrestrial to 15 cm tall. Leaves elliptic, to 6 cm long, to 1.5 cm wide, held at ground level. Flowers to 12 mm wide, greenish-brown, labellum callus black; winter to spring. Lateral sepals with short thickened clubs on tips. Petals hugging ovary. Labellum diamond-shaped, callus ant-like, covering much of lamina.

NSW.

C. trapeziformis Fitzg. is similar to C. formicifera but the labellum is usually more erect and has fewer calli confined to the base.

C. truncata D.L. Jones and M.A. Clem. is also similar to C. formicifera but the labellum is abruptly cut off at the tip.

Source: Jeanes, J. (2005). Orchidaceae. In: Spencer, R.. Horticultural Flora of South-eastern Australia. Volume 5. Flowering plants. Monocotyledons. The identification of garden and cultivated plants. University of New South Wales Press.