HOUSE FLIES AND BLUEBOTTLES 177 



of the above species, all of which are exceedingly common 

 household pests, is distinguished not merely by a charac- 

 teristic form, but also by habits peculiar to itself. 



Besides these, several other species also sometimes 

 invade our houses, and it must be remembered that in 

 all cases it is an invasion : none of them are home-bred, 

 but all have spent their early life and passed through 

 their metamorphoses out of doors. It would indeed be 

 a disgrace to our civilisation if the interiors of our houses 

 afforded any suitable breeding-ground for such creatures : 

 they are all nurtured amidst putrid and refuse matters, 

 and the mere sight of their hideous, worm-like larvae, 

 commonly known as maggots or gentles, is enough to 

 fill one with disgust and loathing. Most valuable, how- 

 ever, are their labours in this stage of their life : they 

 are the great scavengers of the earth, and contribute in 

 no slight degree to the purity of its atmosphere. Of the 

 other Muscidce, that, in their adult condition, more or 

 less frequently occur indoors, we need not stay to speak 

 now, but will reserve a few remarks about them till the 

 end of the next chapter. The above five species will be 

 the only ones we are concerned with at present, as they 

 will probably be the chief representatives of the family 

 met with in towns. In the country, of course, many 

 others will be added to the list, since an open window 

 in such situations proves to not a few of the other rest- 

 less two-winged insect inhabitants of fields, hedges, and 

 ditches, a temptation too strong to be resisted. But 

 even in such cases, the above species will greatly pre- 

 ponderate. Some years ago, I was staying, in the month 

 of August, at a country house which was suffering from 

 an exceptionally severe plague of flies : they swarmed 

 in every window, of which there were not a few, and 

 made an intolerable buzzing. As they died their carcases 



