Marvels of the Universe 



241 



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I'holo ;.!/] [A'. /. S/nltti. 



PART OF FLY'S FOOT. 



This photo shows a. portion of the Fly's foot under 

 the microscope. The dots are the tubes with sucker 

 ends which enable the insect to walk up glass or 

 over the ceilins- 



of this photograph ; they are better seen, however, in 

 the photograph wliich is on a larger scale and has 

 been made with the special object of showing the 

 sheath and lancets alone. In the actual use of this 

 apparatus, the bite is made with the lancets, which 

 cut out a hole large enough in diameter to allow 

 the exit of sufficient blood for the sucking tongue to 

 be placed into. 



Space will not allow us to deal with an e.xplana- 

 tion of the clubs seen on each side of the tongue, 

 which in all the varieties of flies are probablj' sense 

 organs ; neither will it permit much being said con- 

 cerning the wings, although passing mention should 

 be made of the fact that differences in the position of 

 the veins (as the linear markings are called), their 

 arrangement and general appearance, offer to the 

 expert a means — in addition to that of size — of dis- 

 tinguishing the House Fly from the others that are 

 frequently confused with it. Mention might be made 

 here also — for want of a better place — of the curious 

 fungus disease so fatal to the House Fly, which 

 causes them to adhere to window-panes and such like. When closely examined, the fly appears 

 as if invested with a white substance which not only covers the body more or less completely, 

 but even spreads to the wings and to the glass adjacent. A portion of a wing highly magnified is 

 shown, in which this creeping fungus can be seen spreading itself as a white, transparent network, 

 winding its waj' amongst the microscopic hairs, reminding one of clover in the way it pushes its 

 wire-like fibres between the blades of grass upon the lawn. 



The wings move with great rapidity in flight. Messrs. Kirby and Spence quote the substance 

 of an anonymous writer, who says that he calculates that a House Fly in ordinary flight makes 

 about six hundred strokes — which carries it about 

 five feet — ever}- second. If alarmed, however, the 

 velocity can be increased to about thirty to thirty- 

 five feet per second. In this space of time, the writer 

 adds, " a racehorse would clear only ninety feet. 

 which is at the rate of more than a mile a minute." 

 The little fly, then, in his swiftest flight, goes, in the 

 same space of time, about one- third of a mile. In 

 conclusion, they further add : "A little calculation 

 seems to show that did the fly equal the racehorse 

 in size, and retain its present powers in the ratio of 

 its magnitude, it could traverse the globe with the 

 rapidity of lightning." 



The breathing apparatus of the fly much re- 

 sembles that of other insects. One of the chief 

 anatomical differences between a mammal and an 

 insect is that in the former the muscles lie outside 

 the bones — as in the human subject, for example ; 

 whereas in the insect the internal organs are en- 

 closed in a sac-like body, made, in many instances. 



[/;'. J. S/iilla. 



I'ltoto hu] 



FLY'S FOOT. 



Portion of the cusKion of a Fly's foot, less highly 

 magnified than the previous photo. It is in bet'ween 

 the little prominences that Bacteria are carried about. 



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