The Cabbage Root Maggot. 513 



cheap tarlatan, and is screwed together for convenience in storing away. It 

 is 7 feet long, 3 feet wide, 3)^ feet high at the front and 2 feet at the back ; 

 the top being made slanting to correspond with the glass roof of the insec- 

 tary. For convenience in examining all parts of the cage, three large doors 

 were made in the front as shown in the figure. The whole frame sets over a 

 bed of earth made in a wooden frame. In this bed the different food-plants 

 of the pest were grown. Although this cage proved a failure as far as breed- 

 ing the Cabbage Fly is concerned, it will prove a valuable addition to our 

 outfit for studying other, less particular, insects. 



In one of these cages we kept growing various sizes of cabbages and hedge 

 mustard from May 20 to August 3 ; and in the other cage several varieties of 

 turnips and radishes were grown during the same period. The plants grew 

 thriftily, and hundreds of the flies emerged from maggots and puparia 

 placed in the cages. But for some unaccountable reason they would not 

 oviposit. It would seem as though in these large airy cages the flies would 

 be sufficiently at home to provide for the perpetuation of their species. And 

 it seemed still more strange, when we found flies coming into the insectary 

 (which is only a similar cage on a larger scale) from out of doors in June, 

 and breeding on radishes and turnips in a similar bed only a few feet away. 



Thus our efforts to rear this second brood of the pest in confinement has 

 this year been a failure. And yet there is no doubt that the flies of this 

 brood soon oviposit and a second destructive brood of maggots appear in 

 July. For in the latter part of June, we found half grown maggots at work 

 on some of the radishes and turnips in a bed in the insectary. These were 

 doubtless produced by flies which appeared in the early part of June, or 

 about the time the second brood of flies appeared in the fields. Further- 

 more, the recorded facts indicate that in certain years in some localities, 

 this second brood is the destructive one. The testimony of Dr. Fitch and 

 Mr. Fyles quoted above shows this. Mr. Fletcher says in 1890: "The 

 greatest amount of injury is caused by a brood of flies which appears in the 

 middle of June and up to about the first week of July." Thus in Canada, 

 the second brood is usually more destructive than the first. 



The natural conclusion from the above facts is that there is a 

 second brood of the pest, which is often equally as destructive as 

 the first ; the flies of this second brood appear about June 15, and 

 the maggots vv^ork in July. And the second brood evidently 

 works in the same manner on the same food-plants as does the 

 first brood ; late cabbage also often suffers in the seed bed. The 

 exceptional habit of mining the leaves of beets, recorded by Dr. 

 lyintner, seems to have been the work of this second brood of 

 maggots. 



The definite recorded knowledge of this second brood seems to 

 end with the maggots in July. When do the flies which are to 

 produce the third brood appear ? 



