6 HISTORY OF INSECTS. 



Among the numerous gnats and flies which feed on blood, 

 these are the most to be feared ; impelled by an insatiable 

 thirst they make their attack, and will have blood ; nothing- 

 can repel or deter them. Whenever the garment of a tra- 

 veller has accidentally slipped aside, and discovered a 

 portion of his skin, however small, that exposed portion is 

 instantly streaming with blood : in the southern parts of 

 Lapland they are less troublesome than in the northern, 

 although clouds of them occasionally appear, perfonning 

 their evolutions in the air. 



The SimuUa seems to have adopted the world for its 

 country : no known land appears to be without it ; all tem- 

 peratures suit it — the polar snows and the blaze of tropical 

 sands. Yet all the flies of wliich travellers complain as so 

 dreadfully annoying, are not Simulice; — many of our 

 commonest gnats have a similar taste for blood. Although 

 from what is related, there can be no doubt that the blood 

 of man is an acceptable food to the SimuUa, yet it is re- 

 markable that the greatest multitudes of these creatures 

 inhabit those bleak, inhospitable, and almost inaccessible 

 regions where the foot of man seldom treads, and where 

 other warm-blooded animals are scarcely known to exist. It 

 is clearly ascertained that the female SimuUcB alone suck 

 the blood of man ; the males spend their lives among the 

 leaves of trees, or settle on flowers, from which they appear 

 to derive nutriment; it is therefore far from impossible that, 

 on the failure of animal, the females also may have recoui'se 

 to vegetable food. 



History of the Ichneumon. — There are many butterflies 

 and moths which increase so rapidly, that, without a check, 

 their caterpillars would, in two or three years at the utmost, 

 devour every gi*een leaf on the face of the earth, and ren- 

 der it incapable of supporting its present inhabitants. The 

 ichneumons are evidently created to act as a check to this 



