58 THE SCOTTISH NATURALIST 



readers must consult Tutt's articles themselves ; brief 

 references to a few illustrative examples are all that can 

 be here attempted. The term migration as applied to the 

 movements of insects is not, of course, used in the restricted 

 sense in which it is now employed in the case of birds, that 

 is, to denote those regular semi-annual comings and goings 

 between their summer and winter haunts in widely separated 

 countries. An insect's life, in the winged state, is altogether 

 too short to admit of the evolution of so advanced a type of 

 migratory habit, seeing it does not embrace even a single 

 round of the seasons. 1 But in both cases the failure of 

 food supply is doubtless, or at any rate presumably, directly 

 or indirectly at the root of the phenomenon. The more 

 or less irregular "migrations" of insects remind one rather 

 of those so-called " eruptions " to which certain species of 

 birds are from time to time liable. What have been thought 

 to be return movements on the part of locusts, and even of 

 butterflies, towards the country whence they or their parents 

 emigrated are on record ; but there is apparently no satis- 

 factory evidence that, even assuming their nature to have 

 been as supposed, they ever succeeded in their object. 



The records of migratory flights and other wanderings 

 on the part of insects are so numerous that it is difficult, 

 when all are interesting, to make a selection. In what 

 follows a bias is naturally shown for sea-flights, and cases 

 in which species having at least a colourable connection with 

 the British fauna are concerned. Many wonderful flights, 

 startling for their magnitude, if for nothing else, that have 

 been witnessed in the two Americas, Africa, and the East, 

 are thus passed over. 



Lepidoptera (butterflies and moths), being the group with 

 which this paper has most to do, are taken first. It is now 

 recognised that we have on the British list quite a number 

 of species that are to all intents and purposes only periodical 

 immigrants. Among the better known are the Painted 

 Lady, Camberwell Beauty, two Clouded Yellows, Death's- 

 head, Convolvulus, Madder and Humming-bird Hawk-moths. 



1 Scudder's assertion that in America the Milkweed Butterfly (Anosia 

 archippus) lives a full year, is discredited (cf. Tutt). 



