FLIGHT OP INSECTS. 203 



breathing-pores through which the air enters and is discharged, 

 and which are generally visible on the exterior of the body of the 

 insect as a series of pores along each margin of the wider-sur- 

 face, are also most admirable instances of Provident Wisdom. 

 For to prevent the entrance of minute particles of dust or soot 

 which, were their orifices widely open, would be continually enter- 

 ing and disturbing the functions of respiration they are generally 

 furnished with a sieve, 

 consisting either of an 

 interlacement of minute 

 branches, as in the com- 

 mon fly, or of a mem- 

 brane perforated with 

 minute holes, as in the 

 larva of the cockchafer ; 

 and thus in every detail 



of insect economy We Spiracle of Common Fly. 



find models of perfection worthy of an Almighty Hand. 



The articulated abdomen, extremely moveable in those 

 insects which sustain the longest and most powerful flight, 

 serves as a rudder, like the tail in birds ; and the wings are 

 invariably situated as near as possible to the centre of gravity, so 

 that the weight they have to carry may be equally balanced, and 

 their task rendered more easy. These organs, so fragile and 

 seemingly so weak, are frequently endowed with wonderful 

 powers, so that in point of celerity many insects, comparatively 

 to their size, fly much quicker than any birds. It has been 

 calculated that the common fly in its ordinary flight makes with 

 its wings about 600 strokes, which convey it five feet every 

 second; but if -alarmed, their velocity can be increased six or 

 sevenfold, or to thirty or thirty-five feet in the same period a 

 speed which emulates even that of the greyhound or the hare. 

 The strength of muscle and nerve requisite for such a rapid 

 action is truly amazing, and beautiful indeed must be the 

 structure capable of exertions such as these ! 



As in the birds, the powers of flight are very unequally dis- 

 tributed among the insects, but always in strict accordance with 

 their wants. Wings would have been perfectly useless to the 

 numerous parasitic tribes, whose sphere of existence is confined 

 to the narrowest limits ; and the countless hosts of creeping or 



