HOUSE FLIES AND BLUEBOTTLES 219 



However exclusive the tastes of their larvae may be, 

 some at least of these flies seem to be almost omnivorous 

 in their perfect stage, and therefore, possibly, food is 

 one attraction which allures them into our houses ; but 

 then again comes the question, "Why these alone? 

 Why do not the abundant supplies man's providence 

 stores up become equally enticing to other closely allied 

 forms, whose tastes and needs one would suppose to be 

 similar ? " Flies generally manage to find out the room 

 in which the provisions happen to be placed, though 

 the aspect of the apartment has certainly quite as much 

 to do with the numbers that find their way thither as 

 the mere presence of eatables. If the room be bright 

 and sunny, the flies will swarm, while the same provi- 

 sions in a dull and shady room will be almost ignored. 

 And again, apart from the occasional intrusion of an 

 unwelcome bluebottle making straight for the cold meat, 

 the bringing in of meals does not usually produce any 

 noticeable increase in the number of flies in the room ; 

 often many of those that are there seem supremely 

 indifferent to the viands that may be displayed, and 

 continue to amuse themselves by sporting about the 

 windows, mirrors, picture-frames, or gas pendants. We 

 must not forget, however, that what is not food to us 

 may yet be so to them, and they appear to find in 

 these various household objects some sort of nutriment, 

 to judge from the industrious way in which, for example, 

 they will travel over the painted window-frames, dabbing 

 their proboscis down with as much persistence and 

 energy as if they were making a most luxurious feast. 

 What is it they get? Is it the varnish, or the oil with 

 which the paint was mixed, or is it the thin film of 

 miscellaneous matter dirt we call it which gradually 

 accumulates on every exposed surface ? On any of these 



