Calyptomyrmex ryderae

Calyptomyrmex ryderae is known from a handful of collections from a single lowland rainforest area of Sarawak. Most collections have been from leaf litter samples while one worker was found in soil on a rock.

Identification
Hairs on head and body thin (essentially the same width along entire length and with blunt tips), gaster weakly punctate, propodeum lacking or essentially lacking spines or angles, petiolar node in dorsal view noticeably wider than long (PetI > 130) and body smaller (HW < 1.05mm).

This species is most similar to Calyptomyrmex asper but differs in having the lateral surfaces of mesosoma and the dorsal surface of head with more numerous, narrower and more closely spaced rugae (the rugae are less numerous, broader and more widely spaced in asper), the hairs on the mesonotum are longer and thinner (they are shorter and tending to be weakly spatulate in asper), the petiolar node in dorsal view noticeably wider than long (PetI > 130) while it is only slightly wider than long (PetI approx. 115) in asper, and the body is smaller (head width < 1.05mm) in ryderae compared to asper (head width > 1.05mm).

Distribution
This taxon was described from Borneo.

Nomenclature
Holotype worker from G. Mulu National Park, RGS Expedition, Long Pala, 4th Dist., Sarawak, Malaysia, 21 October 1977, B. Bolton, lowland rainforest, leaf litter. Paratypes: 21 workers, same data as holotype except 5 workers collected 21 October, 11 workers collected 16 October, 1 worker collected 18 October, 1 worker collected 28 September, 1 worker collected 20 September (soil on rock), 1 worker collected 1 October (leaf litter on log); 6 workers from Gn. Mulu National Park, 4th Dist., Sarawak, Malaysia, June–August 1978, P.M. Hammond & J.E. Marshall, B.M. 1978-49.

Description
Worker description. Mandibles striate along entire length. Eyes with 5–6 ommatidia in greatest diameter. Propodeum in lateral view with spines reduced to broad angles and essentially absent. Propodeal lobes uniform in thickness. Node of petiole in profile higher than and approximately the same size as postpetiole. In dorsal view the petiolar node slightly narrower than the postpetiolar node. Head indistinctly rugose, the rugae forming an indistinct network, with the underlying surface finely but distinctly punctate. Mesosoma and petiolar and postpetiolar nodes with irregular, wavy rugae superimposed over an indistinctly punctate background. Gaster finely and indistinctly sculptured and with a matte appearance. Hairs on head and body erect, uniform in diameter and with sharp or blunt tips. Clypeal fork with thin hairs only, the apical pair slightly thinner than the lateral pair. Colour red-brown, the antennae and legs slightly lighter.

Measurements. Worker (n = 5) - CFW 0.14–0.15; CI 112–115: HL 0.79–0.89; HW 0.89–1.01; ML 0.87–1.00; MTL 0.38–0.45; PetI 134–155; PetL 0.19–0.23; PetW 0.30–0.34; PronW 0.56–0.63; SI 50–52; SL 0.45–0.51.