INSECTS. 297 



times ; and in five days it has attained its full size. When the maggots 

 attain their full size, they change into the pupa state, and remain in that 

 only a few days ; they then become flies, ready to produce thousands 

 more maggots, and afterwards flies, till the whole brood is destroyed 

 by cold. 



We cannot resist an apt quotation on this wonderful little insect : 

 " A fly on the wing is no less curious an object than one on foot ; yet, 

 when do we trouble our heads about it, except as a thing which troubles 

 us ? The most obvious wonder of its flight is its variety of direction, 

 most usually forwards, with its back upwards like a bird, but on occa- 

 sions backwards, with its back downwards, as when starting from the 

 window and alighting on the ceiling. Marvellous velocity is another 

 of its characteristics. By fair comparison of sizes, what is the swift- 

 ness of a race-horse clearing his mile a minute to the speed of the fly 

 cutting through her third of the same distance in the same time? 

 And what the speed of our steaming giants, the grand puffers of the 

 age, compared with the swiftness of our tiny buzzers; of whom a 

 monster train, scenting their game afar, may even follow partridges 

 and pheasants on the wings of steam in their last flight as friendly 

 offerings 1 But, however, with their game the flies themselves would 

 be most in ' keeping' on the atmospheric line, a principal agent in 

 their flight, as well as in that of other insects, being the air. This 

 enters from the breathing organs of their bodies, in the nerves and 

 muscles of their wings, from which arrangement their velocity depends,, 

 not alone on muscular power, but also on the state of the atmosphere, 

 1 How does a fly buz V is another question more easily asked than 

 answered. ' With its wings, to be sure,' hastily replies one of our 

 readers. ' With its wings as they vibrate upon the air,' responds 

 another, with a smile, half of contempt, half of complacency, at his 

 own more than common measurement of natural philosophy. But how, 

 then, let us ask, can the great dragon-fly, and other similar broad- 

 pinioned, rapid-flying insects, cut through the air with silent swiftness, 

 while others go on buzzing when not upon the wing at all 1 Rennie, 

 who has already put this posing query, himself ascribes the sound par- 

 tially to air ; but to air as it plays on the ' edges of their wings at 

 their origin, as with an Eolian harp-string/ or to the friction of some 

 internal organ on the root of the wing nervures. Lastly, how does the 

 fly feed ? The busy, curious, thirsty fly, that ' drinks with me,' but 

 does ' not drink as I,' his sole instrument for eating or drinking being 

 his trunk or suck ; the narrow pipe by means of which, when let 

 down upon his dainties, he is enabled to imbibe as much as suits his 



