Tabanidae 4° 7 



which the fly could scarcely turn. Larger cages are impracticable be- 

 cause the flies spend their time flying from side to side in an effort to 

 escape. 



Jelly glasses approximately 3 inches in diameter, 2 inches deep, and 

 provided with finely perforated tin lids, have been found satisfactory for 

 incubation and rearing cages. Fine sand is placed in these glasses to 

 a depth of % inch and saturated with water. There should be no stand- 

 ing water in the glasses. The correct moisture content for the sand may 

 best be obtained by adding a slight excess of water and then removing 

 as much as possible with a pipette, pushing the pipette under the sand 

 and slowly taking up water till bubbles begin to appear in the tube. 



For incubation the eggs, still fastened to a fragment of the plant on 

 which they were deposited, are fastened to the side of a large cork by a 

 pin through the plant fragment. The cork is then set in the cage in such 

 a manner that the eggs do not touch the damp sand and so that the 

 larvae, upon hatching, will fall directly into the sand. 



Newly hatched larvae to be reared are separated immediately after 

 hatching and placed in jelly glasses prepared as for incubation. The 

 glasses, however, are set with one edge slightly elevated so that a mois- 

 ture gradient is established in the sand. Where large scale rearing work 

 is contemplated it will be convenient to nail strips of lath across the top 

 of the table used. Rows of cages may then be set with one edge on a 

 lath so that their bottoms form an angle of about 15 degrees with the 

 table top. 



Very young larvae should be fed daily. They probably will eat a 

 variety of insects, annelids, Crustacea, or Mollusca, but Crustacea have 

 been found most convenient to use. Crayfish are easily obtained in 

 quantity. The white meat from the abdomen is cut from the shell and 

 divided into pieces the size of wheat kernels. One piece is placed in 

 each cage and the newly hatched larva placed on the meat with a camel's 

 hair brush. If not actually placed on the food the small larva is unlikely 

 ever to find it. To find the larva a slight excess of water is poured into 

 the cage and shaken. The larva and its cast skin, if present, and any 

 residual food will float out. The cage may then be drained by de- 

 cantation and with the pipette. The first few molted skins are very 

 small and are difficult to find unless the sand is very fine and free from 

 small bits of trash. 



A few species, notably T. costalis and T. lasiophthalmus, progress more 

 satisfactorily and with lower mortality if kept in damp soil instead of 

 wet sand. It is much more difficult to maintain soil at the correct mois- 

 ture content, and to find small larvae in it. The soil must be fairly 

 damp but dry enough to prevent lumping or becoming muddy. To 

 locate small larvae in soil-filled cages, the soil must be dumped out on 



