Hudson.— On Insect Swarms on Mountain- tops. 335 



further the meeting of the sexes and the pairing of individuals 

 from remote areas. It is obvious that the gathering swarm 

 will be far more easily seen than single insects by the scattered 

 individuals around. The swarming of beetles, &c, round tree- 

 tops is probably to be thus explained. Related to the same com- 

 bination of instincts preparatory to pairing is the driving-off of 

 the winged males and females of ant communities, in response 

 to probably some atmospheric, stimulus which makes itself felt 

 on a single day over a \ast area." In connection with these 

 general deductions by Professor Poulton, it has occurred to me 

 that the few observations of the kind made by myself on New 

 Zealand insects should perhaps be placed on record in the 

 Transactions, especially as the perusal of these brief notes may 

 possibly lead otheis to make fuller and more complete observa- 

 tions of a like nature. 



On the 12th December, 1886, I observed on the highest hill 

 to the south of Wellington Harbour great numbers of one of 

 our commonest beetles, Pyronota festiva, together with a swarm 

 of a common fly, Bibio nigrostigma. These insects were not 

 numerous elsewhere, but were only abundant on the top of the 

 hill. 



On the 9th January, 1893, I observed on the rocks and 

 stones on the top of Mount Enys, near Castle Hill, at an eleva- 

 tion of about 7,200 ft., a large swarm of ladybirds (Coccinella 

 11-punctata). There was no vegetation here which could have 

 afforded food for aphides, and as ladybirds feed exclusively on 

 aphides the inference is that the insects must have migrated to 

 this high and inhospitable peak under the influence of some 

 powerful instinct. 



On the 22nd February, 1903, I observed vast swarms of Py- 

 ronota festiva flying over the birch-trees at the bush-line on one 

 of the western slopes of Mount Earnslaw, at an elevation of about 

 4,000 ft. The afternoon was extremely hot, and the flight of 

 the insects so rapid that I did not recognise them as beetles 

 until after I had netted a few specimens for examination. The 

 beetles must have been present in countless thousands, as they 

 were swarming round the birch-trees and apparently equally 

 abundant at all points along that slope of the mountain where 

 I was collecting. 



I have frequently observed the phenomena of ant -migrations 

 mentioned by Professor Poulton, although I am only able to 

 give three actually recorded instances. These cases prove, 

 however, that the winged male and female ants were being 

 ejected by the worker ants over very extended areas at the 

 same time. It is probable that the flight of these vast swarms 

 of winged ants gives rise, to a great extent, to that humming in 



