NESTING ARCHITECTURE 



food in small pyriform or ovate albuminous growths 

 (Midler's corpuscles), which are eaten by the insects, ap- 

 parently without disadvantage to the tree. They present 

 another example of that interesting form of symbiosis- 

 a comradeship of support and defence which not infre- 

 quently exists between plants and insects. 1 For in 

 return for the nurture yielded by the plant, the ants 

 protect them from the incursions of such enemies as 

 the leaf-cutting Attidie, that defoliate them in their leaf- 



* 



hunting expeditions. 



Our studies of what, for lack of a fitter name, has been 

 called the "architectural' and " engineering'' skill of 

 ants will now return for a while to the great confederacy 

 of the communes of mound-making ants. Let us note 

 the citizens of this large colony of Formica exsedoides, 

 who are adding a story to their communal cone. It is a 

 lively and interesting scene. The utmost activity pre- 

 vails, greatly quickened by a smart shower which has 

 made the building material more available for use; for 

 hot, dry weather had left the soil powdery and un- 

 manageable. 



We soon get an insight of their mode of operating. 

 On the outer surface, especially around the gates, small 

 warts or pillars are thrown up, as though to gauge the 

 height of the addition; and between these the infilling 

 is made with pellets of earth, most of which are brought 

 from the interior, where new galleries and rooms are 

 being excavated. The vehicles for this portage are the 

 insects' jaws, that serve alike for carriage, as basket or 

 barrow, and for digging, as pick and shovel. The irreg- 

 ular faces of these pellets fit into and fasten upon one 



1 See Prof. A. F. W. Schimper's The Varying Relations Between 

 Plants and Ants, Jena, 1888. 



