MODE OF EXCLUDING THEM FROM HOUSES. 195 



by a person who has nothing else to do, to eat a 

 meal is impossible." * 



The mode by which these intruders are excluded 

 from dwelling-houses, is detailed by W. Spence, Esq., 

 one of the authors of that " Introduction" which I 

 have so frequently quoted. I shall use the words 

 employed by him in his communication to the Ento- 

 mological Society : — " If my curiosity was excited by 

 this statement, my surprise was not lessened by 

 being told, in explanation of the apparent impossi- 

 biUty of thus excluding flies from a room with un- 

 closed windows, that in point of fact the openings of 

 the windows were covered with a net, but with a net 

 made of white, or light-coloured thread, and with 

 meshes an inch or more in diameter ; so that there 

 was actually no physical obstacle whatever to the 

 entrance of the flies, every separate mesh being not 

 merely large enough to admit one fly, but several, even 

 with expanded wings, to pass through at the same 

 moment, and that consequently, both as to the free 

 admission of air, and of the flies if they had chosen, 

 there was practically no greater impediment than if 

 the windows were entirely open, the flies being ex- 

 cluded simply from some inexpUcable dread of ven- 

 turing across the thread- work. "f The cause of their 



* Travels, vol. ii. p. 35. 

 t Transactions of Entomological Society, vol. i. p. 3. 



o 2 



