210 JOURNAL OF ECONOMIC ENTOMOLOGY [Vol. 4 



NOTES ON THE LIFE HISTORY AND HABITS OF PEGOMYA 



BRASSICAE 



By W. J. SCHOENE 



Late cabbage is one of the important farm crops in many sections 

 of western New York. In general the crop is profitable. It grows 

 vigorously and thrives on many types of soils, and will usually make 

 a crop even when conditions are somewhat unfavorable. The greatest 

 obstacle to the successful culture of late cabbage is the cabbage maggot, 

 Pegomya brassicce, which attacks the plants while they are in the seed 

 bed. The insects are so abundant some seasons that farmers are not 

 able to grow sufficient seedlings for their plantings. Different methods 

 have been adopted by the farmers to cope with the problem but in 

 general they have not been successful. In taking up this problem it 

 was apparent that no progress could be made in protecting seed beds 

 until there was more definite data regarding the life history of the 

 cabbage maggot, especially the period of oviposition of the first brood 

 of adults. This insect has received attention for three seasons and it 

 is desired to present some of the results of this study. 



Oviposition of the First Brood of Flies 



To determine accurately the period during which the bulk of the 

 eggs are deposited was an important part of the problem. The obser- 

 vations recorded in Table I were made by examining each day, or 

 twice every three or four days a varying number of plants grown in 

 the open field. The usual procedure was to remove the eggs and soil 

 from a number of plants and add other soil containing no eggs. After 

 an interval of a few hours the same plants were examined and the 

 number of eggs noted. The data presented is intended to show the 

 period of greatest abundance. It is probable that our notes do not 

 show the first eggs deposited and it is quite certain that a few eggs 

 were deposited throughout the month of June. 



The Number of Days from Egg Deposition to Appearance of Adults 



Believing that the widely divergent periods mentioned by various 

 workers for the pupal period were unnatural, and that the insects 

 under observation had been unduly influenced by laboratory con- 

 ditions, the following experiment was planned in order to place the 

 insects as nearly as possible under the same conditions as those in the 

 field. In 1909 a number of 8-inch flower pots were filled with steri- 

 lized earth and in each were planted cabbage plants that had been 

 grown in the greenhouse. Before transplanting, the plants were 



