116 CIVIC BIOLOGY 



stockyards and slaughter-houses, public dumps, aud all industries which 

 handle materials likely to breed flies. It is utterly uncivilized and 

 brutish that accumulations of filth, which allow flies to both feed and 

 breed, should be permitted to vitiate the best efforts of thousands of 

 good people, cover their foods and homes with filth, and cause not only 

 annoyance but disease and even death. 1 



The eggs of flies hatch in about eight hours into maggots 

 which feed actively and complete their growth in six or seven 

 days. They then burrow into the ground under a manure pile 

 (hence the need of concrete floors) and transform into brown 

 puparia, from which they emerge as adult flies in three days. 



After coming out as adults they fly about over an area 

 not generally more than one thousand yards in diameter, and 

 feed or drink from two hundred to three hundred times a 

 day for from ten to fourteen days before maturing their first 

 batch of eggs. This actually delivers the enemy into our 

 hands. It means that, with flytraps on every garbage can or 

 swill barrel, and with everything most attractive to flies very 

 carefully kept in these receptacles, not a single fly will succeed 



1 In a large city the writer found, opening on an alley, and within a block 

 of a great open public market, a pile of horse manure, entirely unprotected, 

 at least thirty feet in diameter at the base and fourteen feet high. The outer 

 layer of this whole pile was a solid, moving mass of housefly maggots. 

 A moderate estimate for that pile would be ten barrels of fly maggots, which 

 would make, when they reached their growth and emerged, from twenty to 

 thirty barrels of flies. These flies were swarming black over the meat blocks 

 and meats, fruits, fish, candies, cakes. and pies of the whole market. The 

 market people (some few had electric fans) were wearing themselves out shoo- 

 ing those flies from one to the other and back again. The filth of that manure 

 pile was being carried into thousands of homes with the market supplies. 

 The flies were feeding in the market and in hundreds of kitchens in every 

 direction and going back to the manure to lay their eggs. It is unfair to 

 place on the market people the burden of trying to protect their foods from 

 flies under such conditions. 



The horses in this large stable were kept on the second floor ; the manure 

 could have been cleaned into a hopper opening downward into a dump cart 

 in the alley, and every morning before daylight, by effective civic organiza- 

 tion of the work, it might have been out in the country and at work in the 

 land, a paying proposition instead of an insufferable nuisance. 



