212 



birds were numerically lower than the mite populations on birds in the 

 two treatment groups. 



On day 36, there were significant differences between the mite 

 population means on the treated birds and the control birds (Figure hi). 

 Mite populations on the treated birds were reduced to zero, but the mite 

 populations on the control birds averaged 208.2 per bird. 



The mean egg production by treatment by day is shown in Table 61 . 

 Analysis of production data was run by day and by the 36-day production 

 mean. There was no significant difference in production due to treat- 

 ment shown by either analysis. 

 The Effects of Northern Fowl Mites on Egg Production 



Twelve commercial strains of White Leghorn laying hens on the 

 University of Florida Poultry Science Research Farm in Chipley, Florida, 

 were used to evaluate the effects of northern fowl mites on egg produc- 

 tion. Birds were housed two to a cage in cages measuring 31 by 25 by 

 hS cm and were k] weeks old when the experiment began. 



Two houses were utilized for the trial. House 200 was a California- 

 style house 82.3 m long by 3-7 m wide with the center aisle or, an east- 

 west axis. House 100 was 31. k m long, 9-1 m wide, and oriented parallel 

 to house 200. House 100 was partially enclosed with aluminum siding and 

 wild-bird-proofed with 1-cm hardware cloth. All the hens in house 200 

 and the caged layers housed in the west end of house 100 were utilized 

 for the experiment. The number of hens tested in each house was the 

 same. 



Both houses contained four rows of stair-step cages (Figure 43). 

 Each row was divided into twelve 2^-cage blocks with 12 cages on the 

 upper row directly above 12 on the lower row. The 12 strains of hens 



