DISPOSAL BY BURIAL OF FRUIT-FLY INFESTED FRUIT \) 



DISCUSSION 



The depth at which fruit must be buried to prevent the emergence 

 of adults from unpacked, dry soil cannot be determined by taking the 

 pit of greatest depth from which no adults emerged and declaring 

 that to be the proper depth for the burial of infested fruit, unless 

 there is a larger number of pits in the experiment than the one reported 

 here. The records of the location of the insect material in the soil are 

 especially valuable for this reason. The 27-inch pit of the unpacked 

 series can be taken as an example. Six adults emerged from this pit 

 and only one puparium was found beyond the 7-inch level above the 

 fruit (table 3). This puparium was at the 22-inch level above the 

 fruit, or within 6 inches from the surface of the soil. Only 1 of the 6 

 adults that emerged from this pit could have come from the puparium 

 found at the highest level. Since the puparia next nearest to the 

 surface were found at the 7-inch level above the fruit, some of the 

 adults must have passed through at least 20 inches of soil in order to 

 reach the surface. If the distance traversed by the larva which 

 pupated in the level 22 inches above the fruit is added to the distance 

 that some of the adults must have traversed (20 inches), the total is 

 42 inches. As several inches should be added as a factor of safety, 

 the minimum depth at which fruit should be buried in dry, unpacked 

 soil of this type would be 4 feet. 



The depth at which fruit should be buried in pits when the surface 

 is packed to some extent with a tamping implement can be computed 

 as for the unpacked pits by taking the highest levels at which adults 

 and puparia are found above the level of the fruit and adding the 

 inches of soil through which the larvae and adults passed. However, 

 the factor of packing enters into consideration and, as later experi- 

 ments show, the effect is greater near the surface and extends to about 

 the same depth in all the pits. This is shown by the fact that when 

 the soil was packed the surface of all the pits sank approximately the 

 same distance. The highest level at which a puparium was found 

 in this series was 21 inches above the level of fruit (30-inch pit), and 

 the highest level at which an adult was found was 14 inches above the 

 fruit and 10 inches above the nearest puparium (27-inch pit). Thus 

 larvae and adults passed through at least 31 inches of soil. That no 

 emergence was obtained from the packed series, despite the fact that 

 some of the larvae and adults traveled a considerable distance toward 

 the surface of the pits, can only be attributed to the packing, since all 

 other factors were nearly equal. Until further experimentation, it 

 can be determined from the data that burial under 18 inches of dry, 

 well-packed soil will be sufficient to prevent the emergence of Anas- 

 trepha ludens from burial pits. As a further precaution several more 

 inches of soil might be added. 



An observation indicates that May beetle grubs or adults (Phylloph- 

 aga spp.) and such insects as the emerging nymphs of cicadas may 

 open passageways in the soil through which larvae emerging from 

 buried fruit and adults emerging from puparia might escape. Six 

 pits were empty at the time the observation was made. On the sides 

 of each of these pits the emergence holes of May beetles were found. 

 Some of the beetles were trapped in the empty pits that were covered 

 with cages. One beetle was found dead in one of the emergence holes 

 in the side of the pit. There were 39 emergence holes in the six pits, 



