192 Zoology of Colorado 



obtained from the exudations of certain galls on the oaks, and 

 probably also from coccids and aphids. 



The phenomena of slavery among ants have attracted the 

 attention of many observers. The various varieties of Formica 

 sanguinea, red ants with the lower edge of the clypeus more or 

 less notched, enslave the Formica fusca. This is done by making 

 a raid on the nest of the dark F. fusca, and carrying off the larvae 

 and pupae. The result is to increase the population of the F. 

 sanguinea nest, which thus comes to have a mixed population, 

 red and black. However, the F. sanguinea is still able to work, 

 so perhaps the term slavery should not be used. We have 

 another kind of red ant, the Polyergus, which cannot procure its 

 own food, and is wholly dependent on its slaves the black ants. 

 Polyergus can be distinguished from Formica by the narrow, 

 falcate and pointed mandibles, which fit it well for fighting. The 

 Colorado Polyergus are P. breviceps Emery and P. lucidus Mayr. 



Very small red ants, with only nine joints to the antennae, 

 are Brachymyrmex heeri var. dcpilis Emery. They are common 

 at Boulder under stones. 



The large group of Myrmicidae, with two nodes or joints in 

 the pedicel or petiole of abdomen, has ten genera in Colorado. 

 The most conspicuous species is the mound building Pogono- 

 myrmex occidentalis Cresson, the Bearded Ant. These ants are 

 comparatively large, rust red, with long curled hairs on the under 

 side of the head. The mounds are covered with little stones, of 

 singularly uniform size. The size depends on the ability of the 

 ants to pack them out; if they are too large the tunnel has to go 

 round them. In New Mexico I have found interesting fossil 

 shells on these mounds, and it is alleged that sometimes particles 

 of gold occur. The ants of the genus Pheidole are small, but 

 easily recognized by the enormous heads of some of the workers. 

 They store seeds, and the large headed workers are able to crack 

 them. Myrmica contains the common rather small red ants, 

 and Crematogaster is distinguished by the curious heart-shaped 

 abdomen, convex beneath. Solenopsis molesta Say is a very 

 small ant common in the foothill region. It has no spines on the 

 hind part of thorax. 



