294 THE entomologist's record. 



Europe. In June, 1884, it occurred suddenly and in incredible numbers 

 in Manitoba, and, in early June, 1901, it as suddenly appeared in amazing 

 numbers at Ottawa, Manitoba, and westward to the Pacific, the females 

 laying their eggs immediately on their arrival, as do the immigrants of 

 this species when they visit us. The immigrants in 1901 were supposed 

 to have come from the south and west. Cockle having noticed the species 

 at Kaslo, on Kootenay Lake, B.C., on May 2nd, in thousands, but 

 most of the specimens only stayed a day or two, whilst at the same 

 time in early May countless thousands were observed in California, all 

 flying to the north-east and parallel to the Sierra Madre range (Ayin. 

 Rept. Ent. Soc. I hit., 1901, pp. 54-57). One suspects now that attention 

 has been drawn to the matter that our present uncertain knowledge 

 concerning this subject will, in the course of a few years, become more 

 definite and accurate as reliable data made by competent observers 

 accumulate. The different conclusions arrived at by Scudder and 

 ourselves, both having the same facts before us, is all a matter of what 

 we will respectively accept as sufficient evidence, and Scudder seems to 

 be satisfied to the point of conviction with much less evidence and fewer 

 facts than we require. We suspect that no lepidopterist in Europe 

 believes in any autumnal return movement of Pi/rawcis cardui 

 following a spring invasion of this species into north temperate 

 Europe, yet Scudder writes {Butts. New Em/land, p. 1086) that, 

 in the great migration of Pyraweis cnrdni, in 1879, in Europe, 

 a return movement was made out by Fritsch, who, from observa- 

 tions made from early in July to near the end of October, and by 

 noting the direction of flight of every specimen of the species 

 observed, concluded that there was no prevailing direction until August 

 26th, when and until October 20th, with few exceptions, the prevailing 

 movement was towards the west-south-west and south, or diametrically 

 opposite to the prevailing movements of the swarms in June, and he 

 says: "Here, then, the return movement of butterflies, the apparent 

 absence of which so much perplexed Mr. Belt, was, by careful and 

 minute observations, made clear. It is in no way improbable that it 

 is a regular and permanent feature of all migrations among butterflies. 

 In this instance the collective movement was in the spring, the 

 individual movement in the autumn ; in Anom'a anliifipus the case is 

 exactly reversed. Why may there not be, in many cases, individual 

 movement at both seasons, which has been overlooked for want of just 

 such careful observations?" We have no objection to Scudder being 

 satisfied with this evidence, we only ask him to allow us to ask for 

 more facts, before we ourselves can possibly be satisfied. It is just 

 probable, of course, that natural selection may, in the course of ages, 

 have induced a return migratory tendency, but it is, in the case of 

 insects, and in our present state of knowledge, very difficult to believe 

 that this has been so. The northward spring movement of Anosia 

 arcJiippus is an evident fact, the autumnal swarming,"' although at 

 present quite inexplicable as having any connection with migration, is 



* As bearing on the swarniinp; rather than the migration of the species, Scudder 

 notes (Butta. New England, p. 1085) : " The immense numbers of Aporia crataegi, 

 which, at Easter 1829, made the thorntrees on the promenade at Erfurt look as if 

 hung with white hlos'-oins lias l)oen rr^lnted by Kefersteiu, and the sudden outburst 

 of Neoplasia ineuapiu in Washington Territory in 1882, was, according to Hagen, 

 ' wonderful, and only to be compared with an irruption.' " 



