1887.] 86 



Probable immigration 0/ White Bttiterflies. — I -went over to Hunstanton one 

 day towarda the end of May when the white butterflies were coming out. The day 

 was bright and sunny, but the wind, what there was of it, from the N.E. and cold. 

 On the way Pieris rapcB, with doubtless napi, was common, but not more than a 

 casual specimen or two of P. brassicce was to be seen. But on reaching Hunstanton 

 and in walking along the top of the cliff to Old Hunstanton, I came upon multitudes 

 of the latter species, more I think than I ever before saw together. They were 

 flying about the level ground on the top of the cliff, and settling in dozens on the 

 flowers, but did not seem to be in any such numbers further inland, and as no field 

 of any plant of the cabbage or turnip class was visible, nor any probable food plant, 

 I concluded (and still think) that I had come upon a flight of immigrants immedi- 

 ately after their arrival, and before they had recovered sufficiently to pass inland. 

 The great majority were Pieris brassicce, but P. rapce was also numerous. I did 

 not notice P. napi. These butterflies seem to have taken very nearly the course of 

 so large a proportion of our migratory birds. — Chas. Gr. Baeeett, King's Lynn : 

 August imh, 1887. 



Migration of Insects. — As far as change of abode (wandering or migration in 

 the more limited application of that term) is concerned, many instances are known 

 to entomologists in this country. For example, Melitcea Athalia is well knovra to 

 change its breeding ground from time to time. Again, Ino sfatices frequently 

 changes its head quarters. It may be only from one field into another adjacent 

 thereto ; but in one case which came under my observation, a colony had removed 

 from a certain field to another field half a mile distant. 



Perhaps no one will deny that certain species of moths and butterflies are 

 migratory to the extent of changing their breeding ground either annually or every 

 few years ; but as regards immigration of insects into this country, entomologists 

 are divided in opinion. The facts bearing on immigration are less convincing than 

 those just adverted to, which point to simple migration, and it must be admitted 

 that we have no positive proof that foreign-born insects ever do arrive in Britain by 

 what may be called the direct air line route. I feel assured, however, that when 

 British entomologists, in conjunction with their confreres abroad, set about investi- 

 gating the matter in a thoroughly practical manner, it will be found that not only 

 do many species of Lepidoptera migrate considerable distances, but that several 

 species we little suspect of being other than pure British subjects, are in reality only 

 aliens or the descendants of aliens. 



We have records of clouds and swarms of butterflies and lesser numbers down 

 to single individuals of moths observed over the land and far out at sea ; sometimes 

 the flight has been at a considerable elevation, and in other instances quite low. I 

 think we can hardly question the value of these records as a whole, even if in one 

 or two the accuracy of detail may be doubtful. They appear to establish as a fact 

 that there are species of Lepidoptera which leave the place of their birth and travel 

 far from there. 



That a host of any species of butterfly should lie on the north coast of France 

 waiting for a favourable moment to invade England, I think no one will suppose 

 probable ; but from a point very considerably farther to the south or east, a swarm 

 of butterflies, ay, or moths either, might ascend higher and higher into the air until 



