390 THE MONTHLY BULLETIN. 



included in the operculum which is shown anteriorly on the ventral 

 surface as a flattened area. This is torn off when the fly escapes, 

 leaving a large circular opening. The cephalic spiracles protrude over 

 the front margin as two divergent horn-like structures, and the two 

 dorso-posterior hooks described in the mature larva persist in the 

 puparium. The long pair of tails also remains attached as in the 

 mature larva. In the observed cases several days were required before 

 the pupa formed inside the larval skin. 



GENERATIONS PER YEAR. 



There are apparently five or six generations of this parasite during 

 the season, the number depending upon the climatic conditions. 



