NEW FORMICID.E FROM BARRO COLORADO ISLAND. 



Sculpture, pilosity and color as in the worker. Each ocellus 

 with a black margin internally. Wings yellowish hyaline, iri- 

 descent, with pale yellow veins and pterostigma ; their membranes 

 distinctly pubescent. 



Male. Length nearly 3 mm. 



Head without the eyes longer than broad, with rounded pos- 

 terior corners and somewhat convex posterior border. Eyes and 

 ocelli very large. Anterior border of clypeus produced and 

 rounded. Mandibles well-developed, with triangular denticulate 

 blades. Antennae slender; scapes nearly as long as in the worker; 

 first funicular joint small, as broad as long, remaining joints, 

 except the last, subequal, twice as long as broad, terminal joint 

 somewhat longer. Thorax resembling that of the female. Peti- 

 olar node much lower than in the worker and female. Gaster 

 elliptical, not excavated at the base. Legs very slender. 



Sculpture very similar to that of the worker and female, but the 

 sides of the thorax are smooth. 



Pilosity also similar, but the wings with longer pubescence than 

 in the female. 



Brownish yellow, gaster a little darker, antennae and legs 

 slightly paler; eyes and a spot along the inner border of each 

 ocellus black. 



Described from numerous workers and females and two males 

 taken from several colonies living in the fungus gardens of 

 Sericomyrmex amabilis on Barro Colorado Island, C. Z. 



I have made this ant the type of a new subgenus largely on 

 account of the dentition of the mandibles and structure of the 

 antennal funiculus. One unfamiliar with the smaller species of 

 Megalomyrmex, especially those of the subgenus Wheelerimyrmex 

 would be inclined to regard the new species as a Monomorium, 

 mainly because the stature is so small, the mesoepinotal con- 

 striction so feeble and the lateral ridges of the epinotum are so 

 poorly developed as compared w r ith other species of Mega- 

 lomyrmex, but I believe that there can be no doubt concerning the 

 natural affinities of the insect. Emery states (1921) that 

 there is no discoidal cell in the fore wing of Megalomyrmex, but 

 I have found it present in all the species I have examined. Ap- 

 parently this cell may be either present or absent in the species of 

 Monomorium. 

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