October, '16] BRIDWELL: FRUIT-FLY PARASITE 475 



Irate in their efforts to escape. The cages finally adopted were made 

 from ordinary nursery flats 16x12x3 inches. The flat, as made up, is 

 used for the base of the cage. The cover, or as may be said, the cage 

 itself, is made from the material used for the ends and sides of the flats, 

 cut to make a frame fitting quite loosely into the flat and a top of fine 

 copper wire cloth fastened on with wooden strips like the screen on 

 screen doors. 



A layer of dry sand is placed in the bottom of the box. A basket, 

 made by bending up the edges of j-inch mesh wire screen, and fitting 

 easily into the top, is filled with a single layer of the fruit employed. 

 The test tubes containing the parasites and some leaves with honey 

 and water dotted over them, are placed on the fruit. The cotton 

 plugs are removed from the tubes to permit the escape of the parasites 

 and the top is quickly put in place over the basket of fruit and pressed 

 firmly down into the sand which effectually seals the cage and prevents 

 the escape of parasites or the entrance of ants. The maggots emerging 

 from' the fruit cannot penetrate into the sand to any great depth. The 

 wire basket prevents the fruit, wet from the oozing juices, from coming 

 into contact with the sand and caking it so as to interTere with the 

 sifting of the pupae from it. When it is desired to remove the para- 

 sites this cage is opened in the insectary and after a time they will go 

 to the window. The insectary of the Board of Agriculture and Forestry 

 has a room admirably adapted for the purpose. For such use a room 

 should have the following qualifications: It should be small, should 

 have a shelf-table built in tightly against the base of the window oc- 

 cupying the side of the room above the table, in the northern hemis- 

 phere, with a northern exposure. There should be no other strong light 

 and the interior should show no cracks or crevices and should be painted 

 white. The ceiling should be everywhere in easy reach standing, a 

 narrow shelf should extend around the room and ample ventilation 

 can be provided with small openings covered with very fine mesh 

 copper wire screening. 



The method described is a practical one and permits the production 

 of large numbers of parasites with facility but it has the disadvantage 

 of not permitting observations to be made upon the actions of the 

 parasites. Mr. C. R. Pemberton of the Federal Bureau of Entomol- 

 ogy, who is at present engaged in a detailed study of the life-history of 

 the Opiine fruit-fly parasites, and has already secured most interesting 

 and valuable results from his work, has been able to secure partial 

 mating and satisfactory oviposition by the use of the dried fruits in 

 small quantities in glass. The mating seems to be more successful in 

 the larger tubes he has used for the purpose. 



A series of experiments were carried on in the spring of 1914 to 



