MIGRATION AND DISPERSAL OF INSECTS 1 LEPIDOPTERA. 157 



It is of course well known that P. canhti flies all through the winter 

 in the north of Africa from Egypt to Algeria, laying its eggs and con- 

 tinuing to raise its broods during this season, and that it is usually 

 very abundant in the imago state in March and April. 



This migration was noticed as far north as the 50th degree of 

 latitude, and an unusual abundance of the species was observed over 

 the whole of England, Germany, Hungary, and even as far north as 

 Finland, where all the early arrivals were remarkably Avorn and faded. 

 In Wiirtemberg, from June 1st to 8th, a continuous and incessant 

 stream of migrating individuals passed from the south and south-west, 

 to the north, north-east, and east. At Wettsweil, on June 7th, it was 

 estimated that 11,000 specimens passed an observer in the course of 

 the day. On the same day flights were noticed at many places in 

 south-west Germany, Switzerland, and Moravia, and near Ziirich 

 another observer estimated that 1000 passed over his head in eight 

 minutes. On the 9th a swarm passed Morges and Lausanne, their transit 

 occupying almost four hours. On the 10th they were seen at Carlsruhe, 

 and on this date the migration was observed by Oberthiir at Eennes, 

 and he calculated that the butterflies moved about 50 metres in ten 

 seconds ; sometimes twenty or thirty would be seen in a single minute 

 following one another without interruption, sometimes four or five close 

 together ; they flew over all obstacles, passing vertically up the walls of 

 houses in their way, always surmounting such obstacles and not passing 

 round them. On the 11th swarms were seen at Nancy and in Savoy, 

 at 600 metres above the sea, and also at Salzburg. On the same day 

 they were observed at Carlsruhe again, and at Stuttgart, and on 

 June 14th the commune of Wetzikon (Canton Zurich) was invaded, 

 the swarm being estimated at a kilometre in width, and as taking 

 two hours to pass, the insects flying from 2-10 metres above the 

 ground, and moving in a north-westerly direction. In Upper Austria, 

 on June 11th, vast numbers passed incessantly from south-west to 

 north-east, between 1 p.m. and 2 p.m. (ninety to a hundred per 

 minute were counted in a breadth of one hundred paces), whilst still 

 more to the west, at Geneva, a swarm is reported to have obscured the 

 sun for several minutes, and on the 8th, at Bisheim, in Alsace, they 

 were also so abundant that the light was partly obscured. Still 

 farther west, and going back in point of time, from June 3rd-9th, 

 great swarms were observed flying northwards at Strasburg, Avhilst at 

 Angers, on the 10th, myriads passed from east to Avest against the AAdnd, 

 traA^elling at a little distance aboA^e the ground. On the 10th the insect 

 appeared in great abundance in England, and about the same time in 

 Belgium. On the 12th it AA^as obserA'ed at Lautschitz, in Bohemia, on 

 the 15th at Augsburg, and again at Salzburg, passing betAA^een four 

 and fiA'e o'clock in the afternoon, at the rate of about 750 butterflies 

 in an hour. Streams of them Avere noticed every day from the 10th 

 to the 16th, near Paris, being especially abundant on the 15th. After 

 this date the observations chiefly refer to the localities in Avhich 

 various parts of the migrating broods had settled. 



There can be no doubt that our British Adsitors AA'ere part of the 

 great flocks that AA'ere obserA-ed in the act of dispersal at this time. 

 HoAV far these reached to the south and east AA^as not ascertained, but 

 a Painted Lady AA^as seen at the time sunning itself on the bare rocks 

 in the Great Desert of Nefud in Central Arabia, " at least 400 miles 

 from any place Avhere the larva could have fed up." 



