310 



brood moths by 27th April, which however was completely checked 

 by a succeeding long period of cold. The late, cold spring and early 

 summer of 191(3 deferred the first appearance of moths till 26th May, 

 similar weather conditions in 1917 checking emergence till a still 

 later date, 15th June. 



The appearance of the second brood did not follow uniformly from 

 these dates, but in its turn depended on the kind of weather experienced 

 during the summer months. Thus in 1914 the second brood appeared 

 on 19th July and the first eggs were deposited 8 days later. In 

 1915 the date was 26th July, and eggs were first noted 14 days later. 

 The wet cold summer of 1916 resulted in very few second brood moths 

 appearing, and those very late, not until 18th August, a large pro- 

 portion of this generation hibernating as larvae, while the few eggs 

 that were deposited were found about a week after the emergence 

 of the moths. In 1917 a very backward early season accompanied 

 by much rain checked the emergence of the first brood till 15th June, 

 but continued warm settled weather throughout the summer resulted 

 in the appearance of the second brood on 3rd August, followed by 

 oviposition 5 days later. 



Lead arsenate sprays remain efficacious after application for 20 

 days at the most. Egg-hatching usually attains its maximum activity 

 10 to 12 days after the hatching of the first eggs, and this takes place 

 with uniform regularity 2 or 3 days after deposition. For these 

 reasons a spray should be applied shortly after the first eggs of the 

 second brood have begun to hatch out, the dates recommended for 

 spraying in the years under discussion being 27th July, 1914 ; 12th 

 August, 1915 ; 28th August, 1916 ; and 12th August, 1917, together 

 with an extra spray on 5th September, 1917, owing to the fact that 

 a warm autumn induced hatching to continue till the apple crop 

 was harvested. 



As the general practice in the past has been to spray for control 

 of the second generation between 25th July and 1st August, which 

 would have been efiective in only one of the above years, the necessity 

 for annual, regional observations is obvious. 



Maxson (A. C.)- Some Factors Influencing the Distribution of Pemphi- 

 gi(s betae, Doane, in Beet Fields.— JZ. Ecoti. Entom., Concord, N. H. 

 xi, no. 2, April 1918, pp. 231-236. 



During 1916 a preliminary field survey was made of the factors 

 determining the dispersion and distribution of Petnphigus betae (sugar- 

 beet root-aphis) o-^dng to the annual loss of several hundred thousand 

 pounds sustained by the sugar-beet industry due to its attacks in 

 Colorado. The points chiefly studied were the influence exerted on 

 the degree of infestation by previous crops, by the presence of the 

 winter host {Popvlus angustifoUa), and by the time factor. 



As regards this last it is certain that the original infestation in all 

 beet fields is due either to the hibernating wingless individuals or 

 to spring niigrants from the winter host. That being so, the number 

 of infested beets should not increase after the migration from the 

 winter host ceases, unless the Aphids migrate from beet to beet in 

 the field. Observations have proved this to be the case, the infesta- 

 tion increasing from 68 per cent, to 100 per cent, within a fortnight, 

 owing largely to irrigation. 



