514 Bulletin 78. 



Upon pulling up a turnip in a bed in the insectary on July 5, we found 

 several nearly full grown maggots at work on it, and in the soil near by were 

 a few puparia. Flies emerged from these puparia, July 16 and 20 ; the 

 maggots produced flies on July 29, August 2 and 21. Thus the indi- 

 cations are that some of the puparia of the second brood give out their flies 

 in about 20 days, while others remain as puparia for 40 days or 

 more. As has been mentioned, the flies from the first brood of pu- 

 paria also appeared at similar irregular intervals. Possibly a majority of 

 the flies of the third brood (that is, those flies produced from the second 

 brood of maggots) appear in the latter part of July. And curiously enough, 

 some, possibly 20 per cent, of the puparia of the first brood gave out the 

 second brood of flies in our cages about July 20; there had been no maggots 

 in the cages and no flies had appeared since the middle of June. 



Thus a portion of the third brood of flies emerge in July and are 

 seemingly reinforced by a few belated members of the second 

 brood. From this point our knowledge of this pest, both from the 

 records and from our observations, is very meagre and fragmen- 

 tary. The flies which emerge in July would be just in time to 

 catch the late crops of their food-plants, and often the plants are 

 then young and tender. But it is the universal testimony of gar- 

 deners that late crops of cabbages, radishes, or turnips suffer but 

 very little, if any, from the maggots. Especially is this true of 

 cabbages ; some gardeners tell us the maggots seem to prefer to 

 work on late radishes and turnips, and that these crops are the 

 breeding places of the later broods. 



In August, when the third brood of maggots would naturally 

 appear, the early crops of cabbages, cauliflowers, radishes and 

 turnips have been harvested. And as the late crops of these veg- 

 etables seem to be rarely, if ever, seriously damaged, the question 

 naturally arises, if there are later broods, where do they develop ? 



There is no doubt that the maggots do work on the roots of their ordinary 

 food-plants later in the season. Many writers record the occurrence of the 

 insect after August, sometimes even in November. In 1891, the maggots 

 wrought great destruction in a field of turnips at Ilhaca in the early part of 

 the season ; and we found a few maggots still at work on October 3. But 

 there are apparently no records of the maggots occurring in sufficient num- 

 bers to do serious damage after August i. Thus no well-marked destructive 

 broods of the insect seem to appear after the second one, on cultivated crops 

 at least. Those found at work in August and later would seem to be scat- 

 tered remnants or irregular broods produced by belated flies from the first 

 brood of maggots, augmented by some flies which emerge from the second 

 brood of puparia in July, Curtis' observations seem to support the view that 



