THE ANTS OF NORTHERN COLORADO 



217 



b) Ocelli distinct. 



a) Metathorax with obtuse spine. Dorymyrmex 



b) Metathorax without spine. 



aa) Node of pedicel flat; frontal carinae diverging posteriorly 

 (fig. 3a). Formica 



bb) Node of pedicel rounded; frontal carinae nearly parallel. 



Myrmecocystus 



Ocelli 



Claw 



Pectinated spur Tarsus 



Fig. 3. — Details of Structure in Various Species. 

 a. Front view of head of Formica rufa L., subsp. rubiginosa Emery; b. Pheidole sp., 

 soldier; note disproportionately large head as compared with the rest of the body; c. Pos- 

 terior leg of Myrmica scabrenodis Nyl. 



II. Pedicel of abdomen 2-jointed (fig. 2/). 



A. Pedicel attached to dorsal surface of abdomen (fig. 2d). Cremastogaster 



B. Pedicel attached to middle or to ventral surface of abdomen (fig. 1). 



1. Antennae 10- jointed; very small ants. Solenopsis 



2. Antennae n- or 1 2-jointed. 



a. Beard present on head (fig. 2/). Pogonomyrmex 



b. Beard not present on head. 



a) Some individuals of colony with head disproportionately large as com- 

 pared with body (fig. 36). Pheidole 



