368 Journal of Agricultural Research voi. vi. no. 10 



METHODS OF BREEDING AND REARING 



The adult parasites used in all experiments were kept in modified 

 forms of the Doten cage.^ One form, used when it was desired to con- 

 fine a number of parasites together, consisted of two large, straight-sided 

 vials of the same diameter, the mouths of which snugly fitted into a 

 paper tube i inch long. This paper tube was held in shape by a layer 

 of adhesive plaster around the outside. The cage was prevented from 

 rolling by sticking a square of heavy cardboard to one side of the cqu- 

 necting tube. A label was pasted to the upper side of the tube for iden- 

 tification. One vial was kept dry and clean, while water and honey were 

 supplied in the other. 



The other form of Doten cage, used chiefly for isolating pairs and indi- 

 viduals, was simply a small, straight-sided vial into the mouth of which 

 was fitted the open end of a slightly smaller, straight-sided vial. A 

 small label was pasted on the side of the larger vial for identification. 

 Cages of this kind were prevented from rolling by keeping them in 

 shallow boxes with corrugated pasteboard-lined bottoms. Food and 

 water were placed in the smaller vial. 



In both forms of cages the water and the honey used for food were 

 placed separately in small droplets on the upper surface inside the food 

 vial. The honey used was the extracted form diluted with an equal 

 amount of water. It was necessary to exercise considerable care not to 

 place too large a drop of honey in a cage, because of its tendency to run 

 down on the inside of the vial and to entangle the insects. Fresh water 

 and honey were placed in the cages daily, and at least once a week the 

 food vials of the cages were carefully cleaned to remove dried or soured 

 honey. Replenishing the food and water in the cages once a day seemed 

 sufficient to supply the needs of the parasites. It was often found neces- 

 sary to make up a fresh supply of the honey because of souring or mold- 

 ing, especially in hot weather. Sterilizing the fresh supply by placing 

 the dropper bottle containing it in boiling water for a few minutes caused 

 it to remain sweet and usable much longer. 



BREEDING THE PARASITES 



To determine all the life stages from egg to adult involved the processes 

 of exposing Hessian-fly puparia to parasites, dissecting the parasite eggs 

 from the host puparia, and rearing, in little glass-cell cages devised 

 for the purpose, the resulting parasite larvae on Hessian-fly larvae which 

 were also dissected from puparia. Hessian-fly puparia contained in 

 sections of wheat stems were first exposed to the adult parasites by 

 placing the stems in the vial cages containing the adults. The stems 

 remained in the cage for a day, or until a parasite was seen to oviposit in 

 a flaxseed, when they were removed and the puparia dissected. The 



1 Doten, S. B. Concerning the relation of food to reproductive activity and longevity in certain hy- 

 menopterous parasites. Nev. Agr. Expt. Sta. Tech. Bui. 78, 30 p., 10 pi. 1911. 



