DO ANTS FORM PRACTICAL JUDGMENTS? 335 



upon the water on the inner side of the ditch. After walking out 

 upon this bit of paper and reaching outward with its antennae, 

 the ant returned to the island and picked up a crumb of bread crust 

 three millimeters wide. The ant then walked across the charred 

 paper and placed this bit of bread upon the water just beyond 

 and adjacent to the paper. After standing for a short time upon 

 the outer edge of the crumb and reaching outward with its an- 

 tennae, the ant returned to the island and picked up a piece of 

 wood two millimeters wide by three millimeters long. This the 

 ant placed upon the water just beyond and adjacent to the crumb. 

 Thus there was constructed, extending three fourths of the dis- 

 tance across the ditch, a bridge of three elements. Upon the 

 outer terminus of this partial bridge the ant stood for fully two 

 minutes, reaching continually outward with its antennae. The 

 bridge was never completed. 



The third bit of evidence was afforded by a series of experi- 

 ments performed upon the same colony of Formica fusca. This 

 colony, consisting of three wingless perfect females and about two 

 hundred workers, was brought into the laboratory September 27, 

 1906. It was from the sidewalk of one of the streets of Chicago, 

 where it was located partly beneath the stone and partly in the 

 trash that the ants had heaped up along the edge of the stone. 

 The sidewalk, which was several years old, was composed of con- 

 crete stones at least a yard square and fully six inches thick. The 

 stones of this particular pavement were free from cracks of all 

 kinds. In the laboratory the ants were kept in a nest of the type 

 described above. Compartments C and B were covered with 

 orange glass and compartment A with colorless glass. Through- 

 out all of the experiments the Lubbock island upon which the 

 nest was located was kept littered with bread crumbs, bits of wood, 

 small pieces of egg shell, partially burned matches, charred paper, 

 cotton, etc. For nearly three months the ants of the colony were 

 the subjects of daily experiments upon the sense of hearing, etc. 

 After that, for several weeks, the ants were left to themselves, but 

 the nest was carefully scrutinized several times every day. At 

 all times some workers would be found in apartment B, but the 

 fertile females and the majority of the workers used compartment 

 C (Fig. 1) as a living room. Whatever booty the ants captured 

 was always carried into this chamber. 



