1885.1 233 



seaward. I procured a net and captured several, they all proved to be P. gamma. 

 The next day on going out it was at once obvious that Plusia gamma was not nearly 

 80 abundant as it had been on the day before, and all the specimens that could be 

 seen were very poor. I was at first considerably puzzled, but I finally connected 

 the two circumstances together, and concluded tliat there had been a migration 

 northwards, since that was the direction in which the moths observed on the night 

 before were flying. 



I think, with Mr. South, tliat the extensive geographical range of certain insects 

 is owing to migration. Supposing this be so, we should expect that these species 

 would form a large part of the fauna of islands, distant from the land, and sur- 

 rounded by a deep sea, and, judging from five months' experience of Madeira, 

 this would seem to be the case. Let us take the butterflies of that island ; those 

 I observed were Colias Edusa, very common, January to March ; I also saw on 

 January 15th a light-coloured Colias, but being unable to capture it I could not 

 ascertain the species, it may, very possibly, have been C. Hyale ; Vanessa cardui, 

 V. Callirhoe, this may be regarded as the representative of V. Atalanta in the island 

 (there is a specimen of V. Atalanta, said to come from Madeira, in the British 

 Museum collection, but I doubt whether this species is a native of the island), 

 Lyccena bcetica, in February, at flowers of Pelargonium, and Satyrus xiphioides, 

 also in the month of February, flying round loquat trees and in other situations. 

 Now of these C. Edusa and C. Hyale, probably migrate, and are, at any rate, well 

 distributed ; V. cardui and L. bcetica, are notorious examples of extensive range, 

 and the first, undoubtedly, migrates ; V. Callirhoe is represented even in India by a 

 very nearly allied form (which may be regarded as the typical Callirhoe, and the 

 Madeira insect as its variety, vulcanica, the red markings being paler in the Indian 

 form), and S. xiphioides is very closely allied to the southern form of 'S'. jEgeria. 



With the moths, again, we find Sphinx convolvuli hovering over Pelargonium 

 flowers at night ; Acherontia Atropos is sometimes taken ; Deilephila euphorbia is 

 abundant in the larval stage on the sea-spurge in the month of May ; Deiopeia 

 pulchella is represented by a specimen taken in a corn-field on May 3rd ; Mamestra 

 hrassicce destroys the cabbage as it is wont to do in England ; Leucania extranea is 

 very common ; we have three species of Plusia ; gamma, abundant, aurifera^ one 

 specimen, and chalcites, one taken at flowers of white verbena, on the evening of 

 May 21st, and, as a last example Nomophila noctuella {hyhridalis) is very common. 

 Certainly, most of these are widely distributed insects, and it is very probable that 

 many of them migrate. 



I fancy it is a mistake to suppose that the migratory insects are those 

 which have large and seemingly powerful wings, for in Madeira the genus Papilio, 

 for instance, is wholly unrepresented, and how few, if any, of the P. Podalirius, so 

 common on the continent have reached England, and how rarely is Machaon 

 accustomed to leave his native fen and wander over the country. 



Some Coleoptera also seem to migrate ; I think the genus Calosoma does, but 

 not in numbers ; Coccinella, on the other hand, sometimes forms vast swarms, which 

 astonish the people of the maritime districts (and this genus is represented by 

 numerous individuals in Madeira, two I brought home proved to be C. mutabilis). 

 The water-beetles, too, often fly long distances ; I once had one blown against my 



