vni CASES OF ADAPTATION 135 



absolutely essential for the origination and subsequent 

 development of the most wonderful, delightful, and beautiful 

 of all the living things around us our garden friends and 

 household pets, and sweet singers of the woods and fields. 

 Without the myriad swarms of insects everywhere devouring 

 a portion of the new and luxuriant vegetation, the nightingale 

 and the lark, the wren, the redbreast, and the fairy-like tits 

 and gold-crests might never have come into existence, and 

 if the supply failed would now disappear for ever ! 



The Uses of Mosquitoes 



If now we go beyond our own country and see how birds 

 fare in distant lands, we find the key to many of the secrets 

 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 larvae 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 abundant in many parts of 

 the tropics, yet their fullest development is to be found in 

 the icy plains of the Far North, especially within the Arctic 

 circle both in the Eastern and Western hemispheres. 



Sir William Butler in his works The Wild Lone 

 Land, and others on Arctic and sub-Arctic North America 

 describes them as often swarming in such abundance as to 

 completely obscure the sun like a dense thunder-cloud ; 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 



