266 INSECTS. 



with a greenish hue, and marked with numerous angular 

 cream-coloured spots. The Butterflies in this family 

 are remarkable for their short, abrupt flight, whence they 

 derive their common name of Skippers. 



The flight of Butterflies varies greatly in different 

 families and genera. Those with the greatest power of 

 flight are found among the richly-coloured species in the 

 second family, Nymphalidee, the Tortoiseshells, Peacock, 

 Eed Admiral, &c., one, the Purple Emperor, exceeding 

 all others in this, soaring sometimes completely out of 

 sight. In the same family, among the Brown Butter- 

 flies, are found some also of the weakest fliers, with a 

 habit of keeping near the ground. 



The Small White Butterfly, Pieris Rapee (in the first 

 family), though not reckoned among the strong fliers, 

 distinguished itself about five-and-twenty years ago by 

 flying from France to England in such countless swarms, 

 that accounts of the time speak of the sun being com- 

 pletely hidden from vessels in the Channel, during a pro- 

 gress of several hundred yards, by the clouds of insects. 

 It seems likely that they may have received the assistance 

 of an aerial current on their journey, a strong west 

 wind having arisen shortly after their arrival in England. 



This swarming of certain species of insects in a par- 

 ticular year is a phenomenon which occurs in nearly all 

 the orders, and is one of the problems in natural history 

 as yet unsolved by observation. In some cases count- 

 less myriads make their appearance, as in the case 

 of the Turnipfly recorded by Mr. Smith (p. 159), or 

 the recurring instances of such swarms of Ladybirds. 

 In others, insects more or less rare in some years, are 

 comparatively abundant in others. This has been 

 especially noticed of the " Clouded Yellow" Butterfly 



