MIGEATION AND DISPERSAL OF INSECTS : HYMENOPTERA, TERMITES. 233 



time asking them if such occurred to capture a few specimens 

 and send them to him. From two correspondents living thirteen 

 miles apart, some specimens of this ant were received, together with 

 interesting letters describing two large swarms. These were : — 



(1) A great flight, observed on March 2nd, near the Eangitata Gorge. 



(2) Another large flight, observed on March 10th, at Mount Somers. 

 A small swarm was also observed on ]\Iarch 12th near Ashburton. No 

 one, says this observer, who has not seen a flight of T. nitidnm, could 

 imagine the vast numbers that constitute it. This insect invariably 

 migrates in calm and sultry weather, as it would be quite impossible 

 for this minute and delicate species to do so during the slightest motion 

 of the air. The last great flight observed moved very slowly on its 

 course, whilst the "hum" or motion of the wings was only slightly 

 audible. Great numbers rested on a wire fence for a few seconds, but 

 again rose and joined the swarm, their minute hyaline wings, while 

 resting, sparkling with iridescent hues in the sunlight. 



The abundance of winged ants at certain seasons of the year, and 

 their movement to considerable distances may possibly be due to the 

 necessity for cross-fertilisation. Their ordinary habits tend to keep 

 them well within the limits of their own community ; but at the times 

 they perform their annual migrations the ants from various nests 

 must be pretty well mixed up. The life of a male ant is a very short 

 one, and after fertilisation has been effected the female ant loses her 

 wings. The tendency of the males and females to leave the same 

 nest at different times also supports this view. But, apart from 

 this annual dispersal of the newly-emerged males and females 

 that regularly takes place, there is some little evidence that even the 

 wingless forms migrate considerable distances. Darwin describes the 

 movements of a Brazilian ant which migrates in large numbers. He 

 writes: "One day, at Bahia, my attention was drawn by observing 

 many spiders, cockroaches, and other insects, with some lizards, rush- 

 ing in the greatest agitation across a bare piece of ground. A little 

 way behind, every stalk and leaf was blackened by a small ant. The 

 swarm having crossed the bare space, divided itself and descended an 

 old wall. By this means many insects were fairly enclosed, and the 

 efforts which the poor little animals made to extricate themselves from 

 such a death were wonderful. When the ants came to the road they 

 changed their course, and, in narrow files, reascended the wall. Having 

 placed a small stone so as to intercept one of the lines, the whole body 

 attacked it and then immediately retired. Shortly afterwards, another 

 body came to the charge, and, again having failed to make any 

 impression, this line of march was given up. By going an inch round 

 the file might have avoided the stone, and this doubtless would have 

 happened, if it had been originally there, but, having been attacked, 

 the lion-hearted little warriors scorned the idea of yielding." 

 Although Darwin considered these ants were migrating, there is 

 nothing to show that they were not on a simple foraging expedition. 

 Reference should be made here to Bates' account of the Ecitons [Sat. 

 on the Amazons, pp. 360 et sefj,). 



The movements of Hymenoptera which we have described, may, 

 so far as they constitute a change of habitat, be called migrating 

 movements, but they are scarcely to be compared with the migrations 

 over large areas, which we_ have considered in relation to locusts, 



