1913] Pin\us — History and Habits of Spalangia Muscidarum 157 



pupse should then be introduced from time to time to insure having 

 an abundance of fresh material for the parasites to attack. It is 

 very essential that the cage be kept in direct sunlight, for at least 

 part of the day, and in a warm room. A temperature of 75 to 

 80° F. is desirable. In a week or two after the first pupa? have been 

 exposed to the parasites they should be gathered together and 

 placed in a separate place and more fresh pupse added. The 

 original stock of parasites should be secured by collecting puparia 

 in localities where the parasites are known to occur in greatest num- 

 bers. Where great numbers of pupae can be obtained they may be 

 placed together. To facilitate the separation of the puparia from 

 the material in which they pupated, and to eliminate the dead 

 pupae, they may be placed in a vessel of water. All of the living 

 or parasitized pupae float and may be removed with a section 

 lifter or a skimmer. A parasitized pupa can be quite readily rec- 

 ognized by its being much darker than normal and by one side 

 of the puparium appearing almost black while the other portion 

 is somewhat translucent and of lighter color. These puparia 

 should be placed in glass tubes containing a very humid atmosphere 

 and kept in a warm room. As the parasites emerge they should 

 be transferred into breeding boxes as described above. 



When a sufficient number of parasites has emerged to proceed 

 with breeding the other puparia parasitized in the cages should be 

 examined. When it is found that most of the parasites are in the 

 pupal stage the entire lot should be removed to a refrigerator 

 or cold storage room in which the temperature is kept uniformly 

 between 50 and 55° F. These temperatures check development 

 and retard emergence a few weeks before it is planned to liberate 

 the parasites in the field. The puparia should be removed from 

 the refrigerator so they may complete their development. Para- 

 sites should always be liberated near barns or straw stacks where 

 flies are known to be breeding. 



The developmental period can be shortened greatly, probably 

 less than half the time required in the experiments reported herein, 

 by increasing the temperature under which they are propagated. 

 Under natural conditions breeding must be greatly stimulated 

 by the heat produced by rotting straw and manure which surround 

 the parasitized puparia. 



