30 THE KEPOKT OF THE No. 36 



this method to he better suited to our low humidity conditions than, the broad- 

 casting of the bait in coarse drops across the plantations. Several leading growers 

 adopted this method in 1918, and without exception each one reported a very 

 serious loss by the onion maggot, the poisoned bait apparently having failed to 

 influence the degree of infestation. An average field of three acres, for instance, 

 grown under the ordinary cultural methods and treated with the bait in open 

 "pie dishes" yielded only 900 lbs. when a total crop of sixty tons should have 

 been received. Twenty "pie dishes" were used to the acre and they were kept 

 continually moist with bait renewals for the best part of six weeks commencing 

 at tne time when the seedling onions were three inches high. 



These results severely tested our faith in the poisoned bait method of control 

 under irrigated conditions, but with no information as to the habits of the fly 

 under such conditions we decide'd to test the bait more fully in the following 

 years. Hence during 1919, 1920 and 1921. certain life history notes have been 

 obtained at Vernon, B.C., and we take pleasure in presenting them in summarized 

 form together with further results on control operations. 



Life History. 



The individual egg stage lasted from 3 to 8 days. The number of eggs 

 laid in clusters, evidently the product of an individual female's deposition during 

 the height of the spring oviposition period, varied from 3 to 27 on seedling onions 

 and from 11 to 59 on volunteer onions, growing from the remains of the previous 

 year's crop. Solitary eggs were common, clusters of 10 to 15 eggs were frequent, 

 but clusters of 5 to 7 eggs were most usually seen. The most interesting records, 

 which in principle were ordinary, were 59 eggs laid in the soil in a single cluster 

 two inches away from the nearest plant and 39 eggs laid in a cluster on a leaf 

 three inches above the soil surface. 



The individual larval stage varied from 14 to 29 days, during spring and 

 early summer, while the puparium stage lasted approximately the same length 

 of time. Puparia were usually seen between the roots of the plants during th^ 

 summer but, later in the season and in stored onions, pupation frequently occurred 

 between the outer fleshy layers of the bulb or beneath loose epidermis. 



Adult male flies, bred, held and fed in confinement lived from 3 to 13 days 

 and females from 3 to 33 days. Sweeping and breeding records indicated that the 

 sexes were about evenly divided throughout the year. 



During the past three years the first adults to develop from over-wintering 

 puparia in the field appeared at the same time i.e. between May 10th and May 

 15th, at the time when the seedling onions were 1 to 1/2 inches high. In the 

 same three years oviposition commenced in the field between May 16th and May 

 19th and continued into September or until the crop was harvested. 



■Secon'd generation adults, developing from the spring deposition of eggs first 

 made their appearance under field conditions on July 7th, 1919 ; on June 29th. 

 1920, and on June 17th, 1921, and in each year continued to appear until late 

 in August. Second generation eggs, larvse and puparia were present in the field 

 during July, August and September. 



Third generation adults, developing from eggs laid during the first two weeks 

 of July appeared, under field conditions, between August 13th and August 20th 

 and deposited eggs, a few resulting puparia overwintering. 



While the studies necessary to prove the existence of the third generation 

 were successfully negotiated, we are unable to give the exact percentage of second 

 generation puparia that produced third generation adults. Suffice it to say that,. 



