480 PROCEEDINGS OF THE AMERICAN ACADEMY. 



servation, were taken from any ants carrying them, and placed on the 

 floor of the nest, so as to give all ants as nearly as possible an equal 

 chance to pick them up. 



2. Observations. — One hundred observations were made on a single 

 colony of P. piUfera. The other colonies contained no young. In this 

 colony only a few workers (2.6 per cent) were engaged in this activity, 

 no soldiers sharing in it. 



6. Building. 



1. Methods. — In order to watch the ants while building, one cham- 

 ber was provided with damp earth. This was placed on the floor 

 of the chamber, and was of such depth that the ants could not wholly 

 secrete themselves in it. Food was placed in the other chamber. 

 As an aid in counting the ants, the pane of glass which covered 

 the chamber containing earth was ruled into half-inch squares. Ob- 

 servations were made at five-minute intervals in the case of one colony 

 (81); in all other cases the interval was two minutes. At each obser- 

 vation a count was made of all ants of each class which were either 

 digging or carrying earth. 



2. Observations. — One hundred and fifty observations were made 

 on colony 81, and on the others (86, 87, 91) one hundred each. 



Although the per cent of active ants here was somewhat greater than 

 in the activities previously considered, still it was small (0.8, 2, 0.4, 



2). It was not correlated with the whole number of ants in the 

 colony. 



In two colonies (87 and 91) the soldiers did not build at all, and in 

 one of the others (86) the minors were the more active ( 2 per cent > 



1 per cent), in the remaining colony (81) the soldiers were the more 

 active (0.6 per cent <1.4 per cent). Considering all the colonies to- 

 gether, the greater activity was decidedly on the part of the minors. 



7. Surrounding the Queen. 



As there were no queens in any of the colonies of Pheidole pilifera, 

 I was obliged to omit observations in regard to this subject on this 

 species. 



8. Guarding. 



1. Methods. — For the purpose of observing which individuals served 

 as guards to protect or warn the colony in time of danger, the ants 

 were allowed to build a nest of earth in one chamber; food was placed 

 in the other. In order to stimulate the ants and to discover whether 

 any individuals were stationed as guards at the entrances of the earth 



