MIGRATION AND DISPERSAL OF INSECTS I DIPTERA. 177 



covered with flies firmly fixed to the wet paint for a distance of 50 

 yards. The number of a mass of flies 50 yards wide, passing for six 

 hours, seems almost incredible. Newman states {loc. cit.) that he 

 was inundated at the time with notes on the subject. Smith observes 

 {loc. cit., p. 9273) that he saw Sijrphuii pijrastri in thousands at 

 Bournemouth On one of these days a line of dead flies extended from 

 Poole Harbour to Christchurch Bay, a distance of not less than six 

 miles ; their numbers were really incredible. Symes observes {loc. 

 cit., p 9278) that on August 16th, as he went to bathe a mile west of 

 Bridport Harbour, he observed the flies (he calls them " bees ") 

 buzzing around him, and on swimming out about 100 yards he 

 noticed them floating on all sides ; on the same day his son, bath- 

 ing about a mile to the east, observed a similar phenomenon, whilst a 

 boat two miles out at sea was surrounded in like manner. There 

 was a gentle breeze shifting from north to south, and a long drought 

 had preceded the first day of their appearance. Many were noticed in 

 gardens a mile and a half from Bridport on the 21st. Button 

 observes {loc. cit., p. 9333) that, in August, he noticed at Eastbourne 

 many examples settling on flowers, but on August 18th while bathing 

 about fifty yards from shore he passed through a line of them, dead 

 and floating with the tide in an easterly direction ; this line was about 

 a foot in width and from the conformation of the coast at this part, 

 possibly extended for many miles. A few days later on the shore 

 near Seaford he saw a great number of the same insect which settled 

 on any flowers at hand on the beach, and many on his own clothes 

 whilst sitting down to rest. 



In New Zealand the swarming of certain species of diptera have 

 frequently been recorded, although, as to their actual migration little 

 or nothing appears to be known, except in the case of a species of gnat 

 known as Culex argyropus, which is generally accredited by the New 

 Zealand entomologists with migrating habits. Smith observes {Ent. 

 Mo. Mag., xxvi., pp. 320-321) that, on September 19th, 1889, the 

 Lyttleton Times describes a swarm as occurring about eighteen miles 

 from Christchurch. It states that a train " passed through a wall of 

 mosquitoes or midges, three-quarters of a mile in length, twenty feet 

 high, and eighteen inches thick, whilst an entomologist at Ashburton 

 records having observed swarms of less size. On January 15th, 1890, 

 at Tinwald village (near the Ashburton river), the same observer 

 noticed immense numbers of Tipnla novarae in spiders' webs attached 

 to trees and gorse hedges. Great numbers were flying about or 

 moving slowly through the grass, whilst a considerable number were 

 resting. This latter observation appears to us to point rather to an 

 unusual local abundance than to a definite movement. 



This large local abundance of Culicids is not confined to New 

 Zealand and has been recorded from our own islands, althouo-h 

 without any special reference to dispersal being noticed. Thus 

 Haliday notes {Zool., 1864, p. 8920), that Culex pipiens occurs at 

 Holywood in Co. Down, "in multitudes, during the day amon» 

 hedges on the seacoast, in the evening, in columns about the tops 

 of trees, appearing like smoke at the distance of a furlong." Even 

 in the London district such swarms are occasionally met, and 

 Douglas describes {Ent. Mo. Mag., xxxi., p. 239), how, in July 

 1895, for some ten days, Lewisham Eoad, in the South-east London 



