336 Transactions. 



the air frequently noticed on very hot calm days towards the 

 end of summer, and specially mentioned by Gilbert White in his 

 ■'Natural History of Selborne." 



On the 1st April, 1888, whilst collecting on the hills around 

 Kilbirnie, I noticed that a great flight of the winged males and 

 females of A-phcenog aster antarctica was in progress. All the 

 spiders' webs were full of the males, and numerous specimens of 

 both sexes were found crawling on fences and about the ground. 

 The ants were noticed over an area of fully, two miles, but there 

 is no reason to think that the swarming was confined to the 

 country then traversed. 



On the 31st March, 1889, I again observed this ant-swarming, 

 this time over an extensive tract of hilly country to the south 

 of Wellington. The ants were so abundant as to be almost 

 intolerable to persons walking. The weather was very hot, 

 calm, and sunny on both occasions. 



On the 28th. February, 1892, another very hot day, I ob- 

 served, at Karori, swarms of the winged individuals of Aphce- 

 nogaster antarctica. The " humming in the air " was very evi- 

 dent on this occasion, and was no doubt produced by the vast 

 numbers of ants flying overhead. 



Closely allied to the foregoing instincts is that of so-called 

 " gregarious hibernation," which appears to occur in one of 

 our common ichneumon flies, Degithina buchanani, but in this 

 species it seems to be the females only which are thus found 

 congregating. The following observations, made in 1883, have 

 since been frequently repeated. In fact, as recently as May, 

 1903, I found these insects hibernating in large numbers between 

 the weatherboards of my little observatory at Karori. On the 

 14th January, 1883, I observed, whilst collecting at Karori, 

 a number of specimens of this fine ichneumon fly flying in and 

 out of a crack in the bark of a large matai-tree. Being de- 

 sirous of discovering what attracted them, I removed a large 

 portion of the bark, and found that there were over sixty insects 

 crowded together in the hollows and irregularities underneath. 

 I captured several and examined a great number of them, and 

 found them to be all females, there being no difficulty in at once 

 determining the sex in this species. There was no nest of any 

 kind in the tree, the cavity being merely a natural one, the 

 ichneumon flies not having improved on it in any way. On the 

 3rd June of the same year I found a number of these insects 

 under exactly similar circumstances, in the forest about five 

 miles from Palmerston North. There were about a hundred 

 specimens, and they were all females, and seemed quite torpid, 

 this being due, no doubt, to the cold season of the year. On 

 this occasion there were, of course, no specimens on the wing. 



