DISTRIBUTE INSECT VAUIETY. 307 



we are led to surmise an insensible movement of this order 

 within the trades towards the equator, and a corresponding 

 movement beyond their action towards the poles. Local emigra- 

 tion on more confined aerial currents also occurs, and to this 

 source should be due the appearance on these shores of 

 unimported Camberwell Beauties and rare Sphinx Moths, 

 and those files of Small and Large Whites bred in large 

 measure from sea-shore cruciferae on the sand dunes some- 

 times observed crossing the Channel. A flight of the Small 

 White, recorded in Coleman's " British Butterflies ■" (in the form 

 of an extract from the Canterbury Journal for 1846), reached 

 England about twelve o^'clock at noon. During the sea-passage 

 the weather was calm and sunny, with scarce a puff of wind 

 stirring ; but an hour or so after they had touched terra firnut 

 it came on to blow great guns from the south-west, the direction 

 whence the insects came. Towards the middle of July, 1872, a 

 swarm of the Large White enveloped a boat at the mouth of the 

 Weser. Many of the insects were to be seen posing them- 

 selves with erect wings on the watery surface, others lying flat 

 on it as if dead, but flew away rapidly if disturbed. They were 

 accompanied by Dragon-flies [^sckna) , that preyed upon them, 

 and by small flies and ichneumons. A similar occurrence in a 

 neighbouring locality was observed in July, 1868. Among the 

 most regular of our supposed Channel emigrants must be 

 reckoned the Common Clouded Yellows and Painted Lady 

 Butterflies. The first has nearly established itself in the south- 

 eastern counties, although in the opinion of local collectors it 

 sometimes seems to miss a season. The inference is that it 

 comes across the sea from the south-east. It arrives about the 

 end of May in a more or less faded condition, and from these 

 emigrants the butterfly is reproduced in about seven weeks. 

 The most remarkable English migrations on record occurred in 

 the years 1826, 1859, and 1877, when Clouded Yellows became 

 nearly as common as white butterflies all over England, and 

 species turned up in the south of Scotland. In the years 1842, 

 1857, and 1868, Pale Clouded Yellows were especially plentiful, 

 and in 1842 they extended as far as Derbyshire and Yorkshire. 

 In August, 1872, the Camberwell Beauty appeared in nearly every 

 English county, being most frequent in the east of the island. 

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