Lioponera cohici

These ants forage during the day, always in file, over the surface of the ground. Workers raid colonies of Pheidole.

Identification
Diagnsis. A shining, black, medium-sized species closely related to the turneri group of species of eastern Australia. Cerapachys cohici can be easily distinguished from the latter group, which includes turneri Forel, adamus Forel, and larvatus Wheeler, by its more obtuse and rounded dorsal propodeal corners. In cohici these corners form an angle of more than 110° when viewed from the side, while in the turneri group of species they form an angle of 90° or less. P. cohici also bears a fair resemblance to the Australian P. senescens Wheeler, but can be separated from this species by its longer, flatter petiolar node and straighter and more horizontally aligned posterior petiolar teeth.

Distribution
This taxon was described from New Caledonia.

Biology
Ecological notes. All of the collections were made in the rich subtropical evergreen forest clothing the hills that extend from the south bank of the Canala River in the vicinity of the Ciu Falls. The holotype colony was found under a rock in a densely shaded part of the forest, and was occupying a single cavity and adjacent short vertical gallery in the soil. The males were very active and attempted to fly when the nest was exposed. Another colony (acc. no. 246.275) was nesting in open soil at the side of one of the forest trails. The nest entrance consisted of a single five·millimeter·wide opening surrounded by a low, indistinct turret of excavated earth. Lateral excavation revealed three or four galleries leading down from the entrance hole and into soil packed between several buried rocks. At about ten centimeters down two small adjacent chambers had been excavated in the soil against the vertical face of one of the rocks. In these were massed all of the brood and most of the workers. The following rough population estimate was made at the time of collection: 80·100 workers, 40 pupae (in cocoons), 30·40 half.grown to fully grown larvae, and 30 eggs. The ,reproductive of this colony was unfortunately not found. Workers belonging to colony no. 246-275 and other colonies were encountered on several occasions foraging during the day, always in file, over the surface of the ground, and on one occa· sion (no. 190) workers were discovered in the upper layers of a moist rotting log. Twice, workers were observed in the act of raiding colonies of the ant genus Pkeidole. The foraging and raiding behavior of this species will be described in greater detail in a later paper on the general subject of cerapachyine behavior.

Description
Holotype worker. Head width 10.99 mm, head length 1.05 mm, scape length 0.63 mm, cephalic index 94, scape index 64, exposed length of mandibles 0.21 mm, eye length 0.26 mm, pronotal width 0.79 mm, petiole width 0.83 mm, petiole length (measured from the midpoint of the anterior border of the node to the midpoint of the posterior border of the posterior peduncle) 0.63 mm, postpetiole width 0.83 mm, postpetiole length 0.67 mm, width of next gastric segment 1.00 mm. Occipital border very feebly convex in full-face view. Alitrunk viewed from above moderately constricted medially, marginate along the entire dorsolateral border except for an interval of ahout 0.20 mm in the region of the mesothorax. Petiolar node viewed from directly above with strongly concave anterior border, and evenly convex lateral borders, its widest point being about in the middle (see accompanying figure). In the same view the posterolateral teeth extend well beyond the posteriormost point of the posterior node border. Seen from directly above, the postpetiole is widest in the anterior half and is laterally marginate only in the anterior half.

Entire body covered by scattered piligerous punctures spaced on an average of 0.03 to 0.06 mm apart, the interspaces completely smooth and shining. On the sides of the alitrunk the punctures are unusually small, being barely visible at 40X magnification.

Entire body deep blackish brown to jet black, except for the mandibles and gastric apex, which are dark reddish brown. Appendages variably dark reddish brown. Worker variation. Maximum head width of type series (all shown by a single colony, acc. no. 190): 0.88-1.01 mm. The worker type series shows very little variation in other external characters. Male. Head width (across and including compound eyes) 1.10-1.14 mm. Antenna 13-segmented. Mandible well developed, narrowly sub triangular, its masticatory border bearing a large, blunt apical tooth followed basally by an indeterminate number of serial denticulae; the masticatory and basal borders joining through an even, convex curve. Clypeus narrow, its dorsal surface gently convex, its anterior border seen from directly above. moderately and evenly convex. Parapsidal furrows well developed, parallel with each other, and extending anteriorly for about half the length of the scutum. Notaulices absent. Median notal suture present and extending posteriorly for slightly more than one-third the length of the scutum. Wing venation generalized, essentially similar to that of Cerapachys (see Brown and Nutting, 1950, Trans. Amer. Ent. Soc., 75: 132, pI. VIII), differing primarily as follows: Rsf2-3 is lacking, and the second radial crossvein and Rsf5 form a single unit coming off the stigma. The crossvein "x" indicated by Brown and Nutting in the basal cubital-anal region of Cerapachys manni is missing in Cerapachys cohici. Petiole completely lacking the lateral margination that characterizes the Phyracaces worker caste. Seen from above, the node is widest in its anterior half, and its anterior and posterior corners are gently rounded; seen from the side, the node forms a single, even, strong convexity only weakly demarcated from the peduncles. Genitalia completely retractile. Subgenital plate relatively large (exposed length about 0.35 mm), sclerotized, tapering posteriorly to end in a pair of sharp, upward curving hooks each about 0.06 mm in straight length. Parameres short, broadly rounded apically. Pilosity, sculpturing, and color essentially as in the worker. Types. Described from a long series of workers and four males collected by the author at Ciu, near Canala, at 300 meters, and from two kilometers southwest of Ciu, at 500 meters, New Caledonia. The following accessions are included: 190, 246, 263 (holotype nest series), 267, 275, 278, 298. Each represents a separate nest series with the exception of numbers 246 and 275, which are from the same nest. All of the collections were made in the period from December 21, 1954, to January 2, 1955. This species is named for Mr. Francois Cohic, of the Institut Francais d 'Oceanie, an able and enthusiastic student of New Caledonian entomology.