1923 



ENTOMOLOGICAL SOCIETY. 



57 



Relation of Leaf Injury to the Quality of Fruit. The injury to the 

 leaf naturally affects the growth of the wood, but what is still more serious, 

 it affects both the size and quality of the fruit. This season we noticed that 

 grapes on badly infested vines did not attain their full size, and that they failed 

 to ripen properly. Concord grapes instead of having the normal dark blue 

 colour were reddish. As Hartzell has demonstrated by chemical analyses, 

 grape leaf hopper injury has the effect of reducing the sugar and of increasing 

 the acid content. In his experiments he found: (1) "That every sample of 

 Concord from a sprayed section gave a gain in sugar over its mate in the adjoining 

 unsprayed section. These increases varied from 8.4 per cent, to 68.1 per cent., 

 an average of 27.0 per cent." (2) "That in every sample of unsprayed grapes 

 except one, the amount of acid was greater than in the corresponding sample 

 from a sprayed vine. The excess of acid in the unsprayed grapes as compared 

 with those sprayed varied from per cent to 20.6 per cent., an average of 11.2 

 per cent." 



Analyses of Concord grapes this year gave the following results: 



No. 



Treatment 



Brix 



Sacchar- 



ometer 



Dextrose 

 Per Cent. 



Acid Calcu- 

 lated as Tar- 

 taric Per 

 Cent. 



Sugar Ratio 



Dextrose 



Acid 



B. A. R. 



1 

 2 

 3 



4 



Sprayed 



Sprayed 



Unsprayed 



Unsprayed 



16.4 

 16.4 

 11.1 

 12.3 



13.41 



13.75 

 8.62 

 9.76 



.855 



.879 



1.121 



.892 



15.7 



15.6 



7.7 



10.9 



19.18 



18.66 



9.90 



13.79 



Associated Species and Varieties of Erythroneura Comes 



Along with E. comes two other species of Erythroneura and three varieties 

 of E. comes were involved in the outbreak of leaf-hoppers, viz: E. tricincta, 

 E. vulnerata, E. comes vitis, E. comes ziczac, E. comes octonotata. The distribution 

 and proportionate occurrence of the different species and varieties in the Niagara 

 peninsula are shown in table No. 3. 



E. tricincta Fitch. Fitch's description is as follows: 



"Pale yellow with three broad bands, the anterior velvet black, occupying the thorax and 

 basal half of scutel; the middle bright ferruginous ending outwardly in black, forward of the middle 

 of the elytra, the posterior dusky brown on the apex. Length, 0.12 inch." 



Between St. Catharines and the Niagara river tricincta was the dominant 

 species, in fact in some vineyards near the river it almost completely displaced 

 comes. 



Field observations and preliminary insectary experiments indicate that 

 the life history of this species is very similar to that of comes. Some data, secured 

 from a comparative study of two colonies of each of the three species of grape 

 leaf-hoppers, are shown in table No. 2. 



Table No. 2 — Showing Similarity of Life Histories of the Three Species. 



First Brood 



E. Comes 



E. Tricincta 



E. Vulnerata 



Eggs Commenced Hatching 



June 20th 

 July 14th 

 23-25 days 



Aug. 15th 

 Sept. 8th 

 25-26 days 



June 21st 

 July 13th 

 22-23 days 



Aug. 13th 

 Sept. 4th 

 24-26 davs 



June 23rd 



Earliest Nymphs Matured 



Duration of Nymphal Stage 



Second Brood 



Eggs Commenced Hatching. 



Earliest Nymphs Matured 



July 18th 

 26-27 days 



Aug. 19th 

 Sept. 16th 



Duration of Nymphal Stage 



27-29 days 



