The genus Isosoma — Continued. Page. 



Webster's Isosoma {Isosoma irebsfcri How. ) 35 



Description of adult female 36 



The hairy-faced Isosoma {Isosoma hirtifrons How. ) 36 



Description of adult female 37 



Isosoma secale Fitch 38 



Description 38 



Adult female . 38 



Adult male 38 



Fitch's Isosoma {Isosoma fitchii How.) 39 



Description 39 



Adult female - - - - 39 



Adult male ->> 39 



The two-winged grain and grass flies 40 



Were probably originally grass feeders 41 



Early reports of injuries to grain 42 



The greater wheat stem-maggot {Meromyza americana Fitch) 43 



Past history of the insect 43 



Life history 46 



Description 47 



Adult fly, egg, larva, and pupa 47 



Food plants 47 



Selection of food plants by the adults 48 



Place and method of oviposition 48 



Method and nature of attack 49 



Extent of ravages 50 



Preventive measures 50 



Natural enemies - - - 51 



The lesser wheat stem-maggot ( Oscinis carbonaria Loew) 51 



Life history 52 



Food plants 53 



Place and method of oviposition 53 



Nature of injury 53 



Extent of ravages 54 



Description of adult - 54 



Close resemblance to Oscinis soror Macq 55 



Description of egg, larva, and pupa -- 55 



Preventive measures - 56 



Natural enemies 56 



The American frit-fly ( Oscinis soror IMacq. ) 57 



Confusion with other species 57 



Depredations in Minnesota 58 



Life history 59 



Food plants - - - 60 



Difficulties in studying habits 60 



Remedial and preventive measures 61 



Description 61 



Conclusion 62 



