June, '12] CRIDDLE: INSECTS OF MANITOBA 249 



16 adults began to emerge from the above mentioned plant and con- 

 tinued to do so for about a week afterwards l)ut owing to lack of time 

 and unsuitable breeding cages, I was unable to carry them farther. 



In the past it has always been supposed that the Hessian fly was 

 single brooded in Manitoba, but from the above observation there is 

 strong reason for suspecting otherwise. I believe that eventually 

 the life history will prove to be somewhat as follows: Adults appear 

 from over wintering pupae in early spring as soon as the first spring 

 wheat shows above the ground upon which they deposit their eggs, 

 this attack being confined to young plants. The insect reaches 

 maturity about the second Aveek in June, varying of course, with the 

 seasons, and soon after lays its eggs upon stemmed plants from which 

 we have the commonly noticeable breaking down of the stems in 

 late July. Larvae of this generation reach the pupal stage in August 

 to appear as flies the following spring. Much of this surmise has 

 already been partly worked out. 



Injury to grain from Hessian fly was difficult to estimate owing to 

 the similarity of attack to the lesser wheat-stem maggot. It does 

 not, however, appear to have been extensive and very little damage 

 was done by the, presumably, second brood. 



The Lesser Wheat-stem Maggot, Oscinis soror (?). — There are 

 probably few insects that are so persistently injurious to spring w^heat 

 in Manitoba as this. Damage is done by it every year and occasionally 

 to such a large extent as to cause extensive depredations amounting 

 in some instances to twenty per cent. Whole fields will have a patchy 

 appearance as if the grain had failed to germinate properly. An 

 observant person, however, will at once detect the withered plants 

 showing, perhaps a single green leaf remaining, while others will be 

 entirely killed. When dug up plants look as if they had been pinched 

 or chewed near the roots. 



The flies appear in the early spring when plants have made but one 

 or tw^o leaves. Eggs seem to be laid singly or occasionally in pairs 

 close to the ground and the larvae after hatching, at once work their 

 way downwards below the ground where they remain. There is 

 another generation in June and perhaps yet another in. late autumn 

 attacking volunteer wheat and some of the grasses, though I was una- 

 ble to secure flies by sweeping after June. Adults were reared from 

 wheat gathered on May 17, appearing June 12 and for several days 

 after. They were also collected from native grasses, particularly 

 from genus Agropyron and from the now extensively cultivated grass, 

 Agropyron tenerum. 



Injury to grain in some cases amounted to five per cent but usually 

 was much less. Late sown wheat seems to be freer from attack. 



