ANT-NESTS. 195 



easily observed, and have been described in detail by Huber (1810) 

 and Forel (1874). According to Forel, 'They use their mandi- 

 bles in two ways. When closed these organs form a kind of trowel, 

 convex in front and above, concave beneath and behind, and pointed at 

 the tip. This trowel is used for raking up the soft earth and also for 

 moulding and compressing their constructions and thus rendering them 

 more solid and continuous. This is accomplished by pushing the an- 

 terior portion of the closed mandibles forward or upward. In the 

 second place, the mandibles, when open, constitute a veritable pair of 

 tongues with toothed edges, at least in all of the workers of our native 

 ants that do any excavating. They thus serve not only for transporting 

 but also for moulding or comminuting the earth." The forelegs are 

 used for scratching up the soil, in moulding pellets and patting them 

 down after they have been placed in position by the mandibles, and are 

 of so much assistance in this work that when they are cut off the 

 insects are unable to excavate or build without great difficulty and soon 

 abandon their work altogether. 



Ants dislike to excavate in soil that is too dry and friable. When 

 compelled to do this in artificial nests they will sometimes moisten it 

 with water brought from a distance, as Miss Fielde ( 1901 ) has ob- 

 served. She says that the workers of Aphcenogaster picca. " like the 

 Termites, are able to carry water for domestic uses. They probably 

 lap the water into the pouch above the lower lip | the hypopharyngeal 

 pocket] and eject it at its destination. A hundred or two of ants that 

 I brought in and left in a heap of dry earth upon a Lubbock nest, dur- 

 ing the ensuing night took water from the surrounding moat, moistened 

 a full pint of earth, built therein a proper nest, and were busy deposit- 

 ing their larva? in its recesses when I saw them on the following 



morning. 



As even the most extensively excavated nests represent little labor 

 compared with the nests of social wasps and bees, ants are able to 

 leave their homes and make new ones without serious inconvenience. 

 Such changes are often necessitated by the habit of nesting in situa- 

 tions exposed to great and sudden changes in temperature and mois- 

 ture or to the inroads of more aggressive ants and larger terrestrial 

 animals. Barring the intervention of such unusual conditions, how- 

 ever, most ants cling to their nests tenaciously and with every evidence 

 of a keen sense of proprietorship, although there are a few species, 

 besides the nomadic Dorylinse, that seem to delight in an occasional 

 change of residence. Wasmann has shown that Formica san</iiiiica 

 often has summer and winter residences analogous to the city and 

 country homes of wealthy people. The ants migrate from one to the 



