Adelomyrmex coco

An endemic of the Isla del Coco in the Pacific Ocean.

Identification
Adelomyrmex coco shows the least amount of surface sculpture of any known species. The mesosoma is completely smooth and shining throughout. The face varies from longitudinally striate to largely smooth and shining. The mandible is similar to many mainland species in having a differentiated basal and masticatory margin and a distinct tooth at the base of the basal margin, but the masticatory margin only has four teeth instead of the usual five or six. (Longino 2012)

Distribution based on Regional Taxon Lists
Neotropical Region: Costa Rica.

Biology
This species is known only from the evergreen wet forest of Isla del Coco in the Pacific Ocean, southwest of Costa Rica and north of the Galapagos. This is an oceanic island with high levels of endemism. Two of the known workers were collected in forest floor litter samples, and one was collected in a pitfall trap. One of the workers was from near sea level, and two were from cloud forest near the highest point of the island. (Longino 2012)

Castes
Known only from the worker caste.

Nomenclature

 *  coco. Adelomyrmex coco Longino, 2012: 15, fig. 14 (w.) COSTA RICA.

Worker
HW 0.58–0.60 (n=2); mandible with differentiated masticatory and basal margins; masticatory margin with four teeth, apical the largest and three proximal subequal in size; basal margin sinuous with strong tooth at base near condyle, but without notch proximal to this tooth; dorsal surface of mandible with several weak longitudinal striae and several large piligerous puncta; in full face view, lateral clypeal teeth project from beneath clypeal shelf; lateral clypeal teeth confluent with both anterior (ventral) margin of clypeus and transverse carina that forms clypeal shelf, forming vertices of concave triangular space on ventral face of clypeus; median clypeal lobe small, narrow, truncate but not bidentate; hypostomal tooth present as a small denticle; compound eye composed of 6–7 ommatidia; face sculpture highly variable, holotype with fine longitudinal striae covering most of face, with rows of distinct piligerous puncta between striae; one paratype (JTLC000004336) with face largely smooth and shining, with faint longitudinal rugulae on genal spaces medial and anterior to compound eye, and medial to frontal carinae, and with sparse small piligerous puncta on rest of face posterior to compound eye; a second paratype (CASENT0628122) intermediate, with longitudinal striae on anterior half of face.

Short anterior face of pronotum separated from dorsal face by a weak angle; dorsal profile of promesonotum and propodeum forming a single arched convexity, metanotal groove not impressed; propodeal spines short triangular denticles; space between propodeal spines a broad concavity without distinct dorsal and posterior faces; entire mesosoma smooth and shining, with no trace of rugae, dorsal promesonotum with sparse, small piligerous puncta; petiolar node taller than long, subquadrate, with differentiated anterior, dorsal, and posterior faces, distinctly taller than postpetiole; petiole and postpetiole smooth and shiny; postpetiole in dorsal wider than long, with rounded posterior margin; gastral dorsum smooth and shining.

Scape with abundant long subdecumbent pubescence, lacking any longer suberect setae; clypeus and frontal carinae with long erect setae; posterior and posterolateral margins of head with long erect setae; mid and hind tibia with abundant long subdecumbent setae and about three differentiated erect setae that are longer than width of tibia; in profile, dorsal surfaces of head, mesosoma, and gaster with abundant, medium-length, suberect setae; FSH about 0.05, FSI 0.08.

Color light red brown.

Type Material
Holotype worker. Costa Rica, Puntarenas: Isla de Coco, 5.53773–87.05295 ±30 m, 70 m, Feb 2006 (S. Solomon & A. Mikheyev, Transect C) [INBio, unique specimen identifier CASENT0628121]. Paratypes (workers): Costa Rica, Puntarenas: Isla de Coco, 5.52918 –87.07052 ±30 m, 470 m, Feb 2006 (S. Solomon & A. Mikheyev, Transect D) [CAS, CASENT0628122]; Costa Rica, Cocos Island, 5°31.70'N 87°04.21'W, 490 m, Jul 2003 (S. Solomon & A. Mikheyev, transect E pitfall) [MCZC, JTLC000004336].

Etymology
Referring to the type locality.