348 



in less than a week, and the larvae at once enter the growing bulb, 

 where they feed at the lower end. The duration of the larval stage is 

 from two to three weeks, but in seeded onions from the previous year 

 may last four or five weeks [see this Review, Ser. A, iii, p. 569]. Pupa- 

 tion takes place in the soil at a depth of from ^ to 3 inches, or in the 

 outer layers of the onion bulb. The duration of this stage in eastern 

 Canada is about 14 days and in British Columbia varies from 14 to 26 

 days in midsummer. There are probably about three generations each 

 year. The winter is passed in the pupal stage ; adults were first 

 observed at Ottawa in the third week in May. The preoviposition 

 period varies from 10 to 14 days. 



Injury to beans, peas and maize caused by Chortophila (Phorbia) 

 fusciceps, Zett. (corn-seed maggot) has been recorded from Ontario, 

 Quebec, and the maritime provinces. The eggs are probably laid in 

 the soil in which the seeds of the above plants are present and the larvae 

 attack the plants soon after germination. The cotyledons and later 

 the young stem are injured by the burrowing habit of the larva. 

 Turnips, cabbage, onions, etc., and also the eggs of locusts may be 

 attacked. Pupation of larvae collected on 23rd June took place on 

 the following day close below the surface of the soil ; the first adult 

 emerged on 2nd July and the last on 9th July. Later generations, 

 the number of which is unknown, probably attack plants other than 

 peas, beans or maize. In the United States the insect probably 

 hibernates in the adult stage. 



Experiments on the control of the root-maggots described above 

 have shown that tarred felt paper discs placed around the plant as 

 soon as possible after setting out are most effective. Frames made 

 of cheesecloth are also useful for protecting seedUngs, and this measure 

 may be supplemented by the growth of a trap crop of radishes. The 

 success of autumn planting of cabbages and cauliflowers depends 

 largely on the weather conditions in the following spring ; favourable 

 conditions for the development of the larvae would lead to a heavy 

 infestation of such crops. Two or three applications of white hellebore 

 or pyrethrum powder in a dry or liquid form afford a considerable 

 degree of protection. Carbolic emulsion has also proved satisfactory. 

 This is prepared according to the formula :— 1 qt. soft soap, 1 pt. crude 

 carbolic acid, 1 gal. water ; the stock solution is diluted 35 times 

 before use. Turnip and other seed should be sown thickly, since the 

 eggs are then more scattered. The use of hellebore, etc., against the 

 onion maggot is not practicable under field conditions, but the adults 

 can be attracted during the pre-oviposition period by a sweetened 

 arsenical spray [see this Review, Ser. A, iii, p. 570]. Carbolic emulsion 

 is probably of no value against C. fusciceps in peas and beans ; the 

 seeds should not be planted more than 1 or 2 inches deep and in well 

 prepared soil. Crop rotation should be practised. Seedlings should 

 be transplanted with a quantity of soil round the roots to prevent, as 

 far as possible, the burrowing of the larvae into the stems. Deep 

 ploughing in the autumn destroys numerous pupae in the soil, but 

 where crops are cultivated through the winter, infested plants should 

 be removed and destroyed. 



The following parasites have been reared in Canada from C. hrassicae : 

 Baryodma ontarionis, Casey, Cothonaspis gillelti. Wash., Pacht/crepoideus 

 diibius, Ashm., and the Ichneumon, Hemiteles rujicoxus, Prov. 



