The Currant Fruit Fly. 223 



were put at the bottom of all of the holes, except the hole three 

 feet deep, in which 100 puparia wre placed. The insects were 

 ready to emerge from these puparia, for some of the adults had 

 already issued in the breeding jars a few days before burying 

 them. Clay was tramped into the holes one-half and one foot 

 deep. Another hole one foot deep, was filled with loose wet 

 clay, while loose dry clay was placed in the pit two feet deep. 

 The hole three feet deep was filled with large lumps of day. 

 Directly over the filled holes cages were placed, so as to capture 

 any flies which would burrow through the earth. Not a single 

 specimen was found in any of the cages. The clay became hard 

 and compact due to rains, and the surface soil baked into a hard 

 crust, and these conditions probably prevented the imagoes from 

 burrowing completely through the ground. It should not be 

 assumed, however, from this experiment that the pest would 

 not be able to burrow through other kinds of soil. We (1914, 

 pp. 198-199; 1915, pp. 78-83) found that other species of Try- 

 petidae worked their way through two feet of filled earth and 

 four feet of dry sand. 



Sifting Puparia from Soil. 



An attempt was made to sift the puparia from the soil under 

 four currant bushes instead of removing and replacing the 

 ground. The earth was first sifted through a one-quarter inch 

 mesh wire netting, so as to break up the lumps and to remove 

 the roots and grass, then as much of this soil as possible was 

 passed through a mosquito wire. The dirt which failed to pass 

 through the mosquito wire sieve, was spread on white paper in 

 the laboratory and 1927 puparia M^ere counted. After removing 

 as many puparia as could be found, the ground was placed in 

 breeding cages in the insect-house and 60 male and 57 female 

 fruit fli'es emerged from May 16-28. A cage was placed over 

 one of the currant bushes and 221 adults, — 114 males and 107 

 females — issued from May 25-June 11. It was discovered later 

 that the smaller puparia pass through the meshes of the mos- 

 quito wire and this gives a reasonable explanation for the emer- 

 gence of the 221 specimens in the cage. Sifting the soil through 

 wire netting with meshes smaller than screen wire would be an 

 exceedingly laborious task. 



