DISTRIBUTE INSECT VARIETY. 30] 



insect tracheal system here conferring increased capability, whether 

 as regards traversing the air or resisting immersion. Migration 

 is more or less checked, on the other hand, by natural barriers, 

 such as mountain-chains and watery expanses, and the beech-line 

 and Alpine snow become the wreck-chart of many species. The 

 effect of migration is change in the habitat, food plant, or habit 

 of the species. 



Pj/rameis cardai and its varieties sunning on the thistle 

 bank is a cosmopolitan feature in terrestrial scenery we cannot 

 fly from ; it meets us like a friend far from our native land on 

 every gravelly waste, where the gardens of coral islets, deep in 

 the dark Pacific, are overhung by the bread-fruit, or where the 

 dusty sands of Africa and lone savannas of America are im- 

 printed by the hoof of the antelope and buffalo, where the 

 jungle of Bengal echoes to the roar of the tiger, or where the 

 Ceylon elephant crushes through the cane, on ancient lands where 

 the epiornis roved and the emu wanders. Go where you will, 

 there persistently sits the ubiquitous Painted Lady on its heap 

 of shingle or flower-head, just as the Chinese, in their country of 

 gardens, depict it on the rice-tree's pith, from where the eternal 

 snows scarcely melt beneath the spring-tide, to where the equator 

 kindles its glowing heats. 



The history of this marvellous distribution cannot remain 

 wholly a sealed scroll to the geologist when we take into con- 

 sideration that the insect in its wonderful migrations manifestly 

 affords the thread with which to retrace and unravel the problem, 

 while they, on the other hand, render equally patent the reason of 

 its present micertainty of appearance in various localities. Thus 

 at the present day the migrations of the Painted Lady take a 

 fixed direction in the Northern Hemisphere from the Tropic 

 towards the Pole. " It was,'' says Colonel Drummond Hay, 

 " as far as I can recollect, in the early part of the summer of 

 181^, while stationed in Vido, a small island in the harbour of 

 Corfu, that an extraordinary flight of the Painted Lady butterfly 

 took place. The first part of the column reached the island 

 about nine o'clock in the morning, and continued steadily to 

 advance in rolling masses of many thousands for upwards of 

 three hours. Though the density of the column was at no time 

 very great, yet it appeared to extend in breadth as far as one 



