10 BULLETIN NO. 200^ U. S. DEPARTMENT OF AGEICULTUEE. 



can not be overcome. In the first place, some trouble resulted from 

 smaller particles of manure sifting tbrougb between the cross strips 

 and accumulating in the water below. This was especially the case 

 when sawdust and shavings were used for bedding instead of straw. 

 If this material were allowed to accumulate there would finally be 

 enough of it to provide a breeding place on the concrete floor, where 

 the maggots should be kiUed by drowning. Much of this sifting 

 could be prevented by placing the cross strips closer together, so that 

 only ^-inch or even J-inch spaces were afforded. It is not at aU 

 likely that J-inch spaces woidd interfere with migration; but in spite 

 of such improvement there would be, even with the most careful 

 handling, a certain amount of straw or small particles of manure 

 which would fall from the sides of the heap or from the fork at the 

 time it was put on the platform. It will always be necessary to clean 

 out the concrete floor more or less regularly, and for this purpose a 

 long-handled stable broom will be satisfactory when the water sup- 

 ply does not permit the use of a strong stream from a hose. To facili- 

 tate the cleaning of the floor the platform should not be less than 

 1 foot high nor more than 10 or 12 feet wide. The soHd matter which 

 happens to be washed into the cistern will decompose in time and be 

 pumped back with the liquid onto the manure heap. 



In dry weather evaporation of the water on the concrete floor \vill 

 leave large areas of floor surface dry. Larvse falling from the manure 

 above onto the dry floor wiU crawl away and can crawl up the vertical 

 sides of the surrounding rim ; in fact, they could crawl up this surface 

 even if it were as smooth as glass. To insure that all larvse are 

 drowned it is necessary to keep this in mind, and every day, when the 

 manure is added to the heap, more water can be supphed if necessary. 

 This operation wiU consume very little time. 



The most serious defect was found in the fact that mosquitoes 

 bred very freely in the water standing in the concrete basin and in 

 the cistern. In order not to have one pest multiplying at the expense 

 of another, it is necessary to run all water out of the concrete floor at 

 least once a week and to clean the floor at this time; if then a little 

 oil is poured over the surface of the liquid in the cistern, mosquito 

 breeding wiU be prevented entirely. This method was used during 

 the last weeks of the experiment with satisfactory results. If the cis- 

 tern were carefully and tightly covered, perhaps the use of oil would 

 not be necessary. 



No counts or estimates were made of the larvae destroyed during 

 October and November. It is known, however, that larvae continued 

 to appear in the water on the floor during the most of October and 

 during the warmer parts of November. On December 10 the manure 

 was examined without removing it from the platform, and therefore 



