CHAPTER XII 



INSECT AN-D VERTEBRATE ENEMIES 



Parasitic Insects. 



Like other insects, the house-fly is subject to the attack of a 

 variety of parasitic enemies and in the course of some investi- 

 gations in 1908 on the house-fly in Illinois, Girault and Sanders 

 (1909, 1910) found a number of Chalcidoid parasites of M. domestica 

 and its near relatives. They all appeared to belong to the family 



Fig. 75. Spalangia sp., a parasite reared from M. domestica, x 20. 



Pteromalidae and three genera, namely, Spalangia (fig. 75), Nasonia 

 and Muscidifiirax were discovered attacking M. domestica and other 

 Muscids, the last genus being previously undescribed. 



In the first of the two papers mentioned the parasite Nasonia 

 hrevicornis, a new species, is described. This parasite, the authors 

 state, is " stolid and serious, little heeding external influences and 

 disturbances, quietly, persistently giving its whole attention to 



