HARVESTING ANTS. 21 



These plants are sometimes found along the sides 

 of miniature gullies and crevices in the rock, where 

 they have been washed by little runlets of water formed 

 in seasons of heavy rain, and thus these interloping 

 plants are occasionally dispersed and brought into 

 competition with the rightful occupiers of the ground. 



Aita structor and A. barbara do not employ any 

 materials in the construction of their nest, simply 

 excavating it out of the earth itself, or occasionally 

 out of the sandy rock, and the large mounds, in great 

 part composed of vegetable matter, which may fre- 

 quently be found at the entrances of their nests, are 

 nothing more than the rubbish heaps and kitchen 

 middens of each establishment. These consist in part 

 of the earth pellets and grains of gravel which the 

 ants bring out from their nest when forming the sub- 

 terranean galleries, but principally of plant-refuse such 

 as the chaff of grasses, empty capsules, gnawed seed- 

 coats, and the like, which would occupy much space 

 if left inside the nest (see Plate I., Fig. A.). While an 

 army of workers are employed in seeking and bringing 

 in supplies, others are busy sorting the materials thus 

 obtained, stripping off all the useless envelopes of seed 

 or grain, and carrying them out to throw away. 

 Thanks to the unwearied activity with which this 

 divided labour is carried on the kitchen middens 

 speedily rise in the harvest season, and in places where 

 they are not exposed to the action of wind and rain, 

 often acquire a considerable size, so much so that 

 sometimes, if collected, one alone might fill a quart 

 tankard. 



It was the sight of such a refuse mound, and an ex- 

 amination of the materials which composed it, — many 



