30 



Amazon. In these cases migrations may perhaps be connected with the question of food, 

 or of the continuance of the species. 



A butterfly which is well known in Canada, and which has a very wide range, is 

 noted for its migratory habits; it is the Danais archippus (fig. 12). Hardly a season passes 



Fig. 12. 



but we read of its migrations. Newspapers in the Southwestern States, and the weather 

 signal officers, were constantly reporting the passage over Iowa, Kansas, Missouri and 

 Texas of swarms of this butterfly during the months of September and October last. 

 Even in Canada they are sometimes seen in great numbers on their way either north or 

 south. I myself have seen the shore of Lake Ontario, near Brighton, strewn with hun- 

 dreds of their dead bodies, cast up by the waves, and which no doubt had formed part of 

 a swarm which from weakness or some other cause had perished while flying across the 

 lake. 



Mr. Riley gives an interesting account of the causes which may lead to the migra- 

 tions of this butterfly in his third report. He says : — " It would be difficult to give any 

 satisfactory reason for this assembling together of such swarms of butterflies. As I have 

 abundantly proved by examination of specimens, the individuals composing the swarms 

 of our Archippus butterfly comprise both sexes ; if anything the females^ prevail. The 

 flights almost always occur in the autumn, when the milk- weeds ( Asclepias), upon which 

 the larva of this butterfly feeds, have perished. The instinct to propagate is, therefore, 

 at the time in abeyance. The butterflies, unable to supply themselves with sweets from 

 flowers, are either attracted in quantities to trees that are covered with honey-secreting 

 plants, or bark lice ; or else they must migrate southward, where flowers are still 

 blooming. The Archippus butterfly hibernates within hollow trees and other sheltered 

 situations. Southerly timber regions offer most favourable conditions for such hiberna- 

 tion. Under the most favourable conditions a large majority perish. A small portion of 

 the females survive the winter. Such hibernating individuals, upon waking from their 

 winter torpor, make at once for the prairie, where the milk-weeds most abound. Faded, 

 and often tattered, they may be seen flying swiftly over such prairies. 



" I have no doubt but that they travel thus for many hundred miles, keeping prin- 

 cipally to the north, and ere they perish, supplying the milk-weeds here and there with 

 eggs. A fresh brood is produced in less than a month, and these extend still farther 

 north, until we find the species late in the growing season as far up as the Saskatchewan 

 country, where it can scarcely successfully hibernate, and from whence the butterflies in- 

 stinctively migrate southward. We can thus understand how there are two, three or more 

 broods in southerly regions, and only one towards British America. 



" The exceptional flights noticed in the spring, and which, so far as recorded, take 

 place quite early and in the same southerly direction, find a similar explanation. They may 

 be looked upon as continuations of the autumn flights. Hibernating in the temperate 

 belt, they are awakened and aroused upon the advent of spring, to find the milk- weeds 

 not yet started, and they instinctively pass to more southern regions. There is a south- 



