48 



The mixture was also used to position the glass chips necessary for 

 coverslip support. At this point, slides were racked and racks placed 

 in a dust-free enclosure tc allow the phenol to evaporate. Three or 

 four days were necessary for the evaporation step to be completed. This 

 step can be hastened by placing slides in an oven at 50 C for 48 hr. If 

 coversl ips are added before phenol has completely evaporated, specimens 

 may be damaged. 



After the phenol had evaporated, coversl ips were placed over the 

 specimens using pure balsam. Slides were set aside until the balsam 

 had dried. 

 Bioassay of Poultry Manure 



Manure for laboratory bioassay was collected in 360-ml plastic 

 cups. Samples were capped and then frozen for a minimum of 24 hr to 

 kill fauna present in the manure. Prior to testing, samples were 

 removed from the freezer and allowed to thaw completely. Twenty-four 

 hours were usually required for samples to reach ambient temperature. 



Unless otherwise specified, manure samples were seeded with flrst- 

 instar larvae of the particular fly species to be tested. Eggs were 

 used exclusively at first but their use was discontinued when first- 

 instar larvae produced more precise results. Manure was never recon- 

 stituted with water. 



After larvae were added, samples were covered with screen and 

 placed in the growth chamber. Adults were allowed to emerge and die 

 prior to examination of samples. Pupae and adults were separated 

 from manure by flotation. 



