i6o 



SCIENTIFIC NEWS. 



[Aug. 17, 1 1 



"There is enough in any one of these inquiries to 

 employ the leisure hours of a man's life if he will give 

 his mind to it. Results of value, however, can only be 

 obtained after many years of close observation, carried 

 on for the most part in the same locality." 



— «->i^«^*^-* — - 



EXTINCT BRITISH BUTTERFLIES, 



And the Continuity of Existing Species by Means 



of Migration Considered. 



{Continued from p. 125.) 



A FEW years ago the common large white butterfly 

 (Pieris brassicw) became remarkably scarce through- 

 out the country, so that entomologists were afraid that it 

 had followed in the wake of the black- veined white (Aporia 

 cratcegi). In the summer of 1884, however (as recorded 

 in the Etttomologist), our gardens were visited by 

 an innumerable horde of this species, and since then 

 it has occurred in tolerable abundance in every locality 

 we have visited. Whether the continuity of this species 

 was maintained by migration from the continent, we are 

 not in a position at present to determine. 



Now migration possesses a far wider influence upon 

 the present distribution of the Rhopalocera in the British 

 Isles than is generally entertained. Many species would 

 undoubtedly die off in the course of a very few years if 

 it were not for the continual stream pouring over here 

 from the continent to take the place of those species 

 which succumb to the adverse influences of our climate. 

 Let us take the Painted Lady Butterfly {Vanessa cardui) 

 as a good instance. 



This insect possesses a wide area of distribution, being 

 found in nearly every country in the globe. It is one of 

 those insects in which a strong migratory instinct ap- 

 pears to be developed. Gathering together in enormous 

 clouds, they quit the place of their birth, and depart in 

 search of " fresh fields and pastures new." 



The Painted Lady produces two broods in the year, 

 and hibernates in the perfect state. When one of these 

 large migratory hordes reaches this country, it generally 

 appears to be composed of those insects that have hiber- 

 nated ; such hordes reach our shores in or about June. 



If the swarm is a large one, the butterflies spread over 

 the island ; if, on the other hand, the swarm is a small 

 one, the range is more restricted. The butterflies then 

 breed and die. The first brood is produced in August, 

 when the imagines again in their turn deposit ova on 

 the thistles and die. In our British climate thistles and 

 kindred plants die early in the autumn, and before the 

 larva can feed on them the chilly nights have withered 

 the food plants. Starved with cold and hunger, the 

 larva fall victims to our climate, so that the second 

 brood, which ought to live over the winter to continue 

 the race over another year, never reaches maturity, and 

 the species disappears. 



It may happen, however, sometimes that a few of the 

 first brood emerge so late that they hibernate or emerge 

 so early that the progeny passes through the various 

 stages and does the same. Either of these occurrences 

 would carry the race on for another season, but it does 

 not seem possible for this to last more than a year or 

 two. The species is then lost until a fresh migration 

 causes it to be abundant once more. 



The year 1879 will long be remembered for the great 

 numbers of this butterfly which were seen in this coun- 

 try. It occurred all over the British Isles, as far north 



even as the Orkneys and the Shetlands. Since that 

 date, however, it has not been seen in abundance in any 

 locality known to us. 



Several species of butterflies which occur in this coun- 

 try are entirely dependent on migration for their appear- 

 ance. These are the Bath white (Pieris daplidice), the 

 two clouded yellows (Colias hyale and C. edusa), the 

 queen of Spain fritillary (Argynnis lalhonia), the Cam- 

 berwell beauty (Vanessa antiopa), the pea-pod Argus 

 (Lampides boetica), and the great American butterfly 

 (Danais archippus). 



In the case of Vanessa antiopa it was formerly believed 

 that the fact of all the specimens taken in this country 

 possessing white borders to their wings, while those 

 on the Continent have yellow borders, was sufficient 

 proof that the former were indigenous to the British 

 Isles. Subsequent investigation and observation, how- 

 ever, have proved beyond doubt that those insects with 

 white borders to their wings are old specimens, being 

 generally those which have hibernated. They more- 

 over also occur on the Continent in spring, whereas it 

 was thought that they were peculiar to this country. 

 In our opinion, therefore, the occasional appearances of 

 this grand insect in the British Isles may be referable to 

 the same theory of continuity by migration as in the case 

 of Vanessa cardui. 



The two clouded yellow butterflies (Colias edusa and 

 C. hyale) have both a great predilection for wandering, 

 and on account of the number which have of late years 

 made their way over from the Continent both species 

 seem to be apparently becoming more plentiful and 

 widening their area of distribution in the British Islands. 

 About fifty years ago both these insects were looked upon 

 as great rarities. They are now however, to be met with 

 somewhere in the country every season. 



The year 1877 will long be remembered as the great 

 "Colias year," when they occurred in this country in 

 immense swarms. 



Their increase may be attributed in some measure to 

 the same cause which is operating just the reverse with 

 such a number of other species, namely, cultivation — the 

 extended cultivation of various tracts of clover by agri- 

 culturists, this plant constituting the pabulum of both 

 species. 



In this country Colias edusa occurs much more 

 commonly than C. hyale, the reverse being singularly 

 the case on the Continent. 



Danais archippus is a species which has the last few 

 years occurred in this country in considerable numbers 

 — chiefly on the south coast. It is decidedly cosmopoli- 

 tan in its distribution, being found over a great part of the 

 globe. In America it is found from the Arctic Circle to 

 the Tropic of Capricorn. Its occurrence in our own 

 country is due, of course, to migration. It is a species 

 that possesses a very powerful flight and is capable of 

 withstanding great vicissitudes of climate, and in addition 

 two species of plants, Vinca major and V. minor, very 

 closely allied to one of itspabula, occur abundantly on rocky 

 places in the south of England ; so that it is not at all un- 

 likely to establish itself over here at some future date, as 

 it has already done in Australia and New Zealand, etc. 

 (To be continued.) 

 — *-«^n^«f-» — 



Injurious Action of Noise. — Dr. W. B. Piatt (Popular 

 Science Monthly) formally recognises noise as one of the 

 chief injurious influences of city life, and makes sugges- 

 tions for its limitation, such as the abolition of church bells. 



