78 A NATURALIST IN HIMALAYA 



danger was removed. Migration at once ceased and 

 the larvae were hurried back to the old nest. A number 

 of ants remained about the aperture searching in all 

 directions for the cause of the calamity. After an 

 hour of fruitless search they must have concluded that 

 all cause for alarm had disappeared, for the ants began 

 to emerge with their larvce from the old nest and the 

 migration again continued in a steady stream. Thus 

 can the migrants modify their behaviour. If they 

 meet with an obstruction, they conceal their larvse and 

 break down the opposing barrier ; if they imagine 

 danger is at hand, they cease their migration and 

 retire to the deserted nest. 



As rain stimulates migration, so also does it awaken 

 the sexual forms which, on emerging from the nest, 

 soon seek union. This takes place under different 

 conditions in different species. In the large Myrme- 

 cocysttis setipes union sometimes occurs on the ground 

 near the mouth of the nest shordy after the males and 

 females escape. It may therefore enjoy no nuptial 

 flight. This is not so with the harvesters, for the 

 males and females of this ant fly away independently, 

 and the probability of union must in this species be 

 more remote, as it will depend on a chance meeting 

 between the opposite sexes at a distance from the nest. 

 The sexual forms of other ants congregate in the air 

 in a regular swarm. The males and females of one of 

 the smaller species of the Myrmecince collected round 

 me one morning in June as I wandered through the 

 fields. They moved through the air like a cloud of 

 insects, and persisted in alighting on my head and 

 shoulders, after which act union occurred. 



The life of the male after it leaves the nest must be 



