48 A NATURALIST IN HIMALAYA 



sealed the crevice through which it had passed and 

 then rejoined its comrades for the night. Without 

 assistance or interference the soHtary worker per- 

 formed this important duty ; the division of labour 

 in the community had reached such a degree of 

 advancement that the specialized toil of one member 

 was to the advantage of the whole nest. 



In this instinct, like all others, are occasional mis- 

 takes and imperfections. I was surprised at one 

 foolish error made by a busy worker when engaged 

 in the evening duty of sealing the entrance. It 

 carefully stuffed its load, transported with much 

 labour, into a blind hole in the ground, presumably 

 under the impression that it was barring the aperture 

 of its nest. 



But the labour of closing the formicary was not a 

 changeless routine as are many instincts in many 

 species. For on a subsequent evening I observed the 

 ants adopting a somewhat different mode of work. 

 Not only one, but a number of workers took part ; 

 and instead of dropping the larger pebbles from out- 

 side down the mouth of the nest, they performed all 

 their work within the orifice and closed the opening 

 by piling up fragments of earth all of which they 

 carried from the interior of the nest. 



As the harvesters cast out the husks of the seeds, 

 so do these carnivorous ants cast out the shells of the 

 insects. At one nest I watched them dragging out 

 shell after shell and piling them up at the distant 

 margin of the excavated earth, and I thought at first 

 that they were wonderful sanitarians for so choosing 

 the furthest limits of their refuse heap for the de- 

 position of their objectionable burdens. But this 



