146 THE WORLD OF LIFE 



of bird-life in the greater or less abundance of insects which 

 supply them with food at the critical season of their lives 

 when they have to supply daily and hourly food to their newly- 

 hatched broods. Amid all the infinite variety of the insect 

 world there is probably no one order which supplies such an 

 enormous quantity of food to birds and other creatures as the 

 two-winged flies (Diptera) whose larvx are the maggots which 

 quickly devour all kinds of dead beasts and birds, as well as 

 all kinds of putrefying animal matter ; but in the perfect state 

 these insects abound in such swarms as also to supply food to 

 whole groups of fly-catching birds. And among these no well- 

 marked and very restricted group is at once so hateful to 

 mankind and so delightful to birds as the mosquitoes. It is 

 commonly supposed that these particular insect-pests are more 

 especially tropical; but though they are no doubt very abun- 

 dant in many parts of the tropics, yet their fullest develop- 

 ment is to be found in the icy plains of the Far Xorth, espe- 

 cially within the Arctic circle both in the Eastern and Western 

 hemispheres. 



Sir William Butler in his w^orks — The Wild Lone Land, 

 and others on Arctic and sub-Arctic Xorth America — de- 

 scribes them as often swarming in such abundance as to com- 

 pletely obscure the sun like a dense thundercloud ; and they 

 furnish abundant material for the wildly exaggerated stories 

 in which Americans delight — such as the serious statement 

 that they can pierce through the thickest cow-hide boots, and 

 that an Irishman, seeking protection from them by covering 

 his head with a copper kettle, they pierced it in such countless 

 numbers that their combined strength enabled them to fly away 

 with it! 



Our best and most instructive writer on the wonderful bird- 

 migrations to the Arctic regions is the late Mr. Henry See- 

 bohm, who spent two seasons there, one in the north-east of 

 Russia, at Ust-Zylma, and at the mouth of the Petchora River, 

 far within the Arctic circle; and another in [N'orthern Siberia, 

 at the mouth of the Yenesay River. He tells us, that — 



