TERRITORY 



171 



The ants were chiefly engaged in "farming" the aphids on the trees 

 and shrubs, especially the birches. Trackways extended from each 

 nest to such trees as seemed to determine the size and form of each 

 territory. Some of the trackways persisted in relation to the same 

 trees for the period of three years, but others changed as a result of 

 invading parties or the apjiearance of new trees. Each nest possessed 



B""~~ -----. 



^^'M 



©5 



Q- 



©10 



/T"! 



/'G 



Fig. 36.— Sketch-map, July 20, 1929, of wood-ant trackways and nests in bird 

 sanctuary at Picket Hill. Black dots are nests; circles with dots are places of 

 former nests; broken hues are trackways; barred lines are fences or hedges; 

 some, but not all, birch trees are put in {B), including majority visited by ants. 

 Track from nest 1 outside the hedge continued 100 feet further west among 

 gorse bushes (G). Approximate positions of willow wren nests in 1929 are showTi 

 by four crosses. (After Elton, 1932.) 



its own distinct system, but there was normally no hostility among 

 the families, and hence no defense of territorial rights was needed. 

 However, the respect for such rights was not sufficient to prevent raids 

 and the destruction of a nest (Fig. 36) . 



Elton's account indicates that the territories observed were pri- 

 marily a consequence of convenience and efficiency. Observations by 

 the senior author of a vast aggregation of harvester ants {Messor 

 species) in a community of Aristida, in the Colorado Desert, indi- 

 cated that there w^re no definite trails and no territorial limits (see 

 Fig. 17, page 83). In a neighboring region where four species were 

 busily engaged in collecting grass fruits, the trackways intersected 



