54 
THE GKAPE ROOT-WOKM. 
The percentage of parasitized eggs in the field varied considerably 
in different sections of the grape belt, as well as in parts of the same 
vineyard. It was always highest where eggs were most numerous. 
This was especially brought out in the different sections in the experi- 
mental vineyards, where the sprayed areas were but slightly infested 
with root-worms. 
Thus, Davidson's vineyard, consisting of 12 acres, located half a 
mile north of the city, showed in 1908 the following results: 
Average 
number of 
Per cent eggs per 
parasitized. vine. 
Unsprayed young Concord vines 18 268. 8 
Sprayed young Concord vines 9. 5 12. 4 
Unsprayed old Concord vines 13.2 319. 2 
Sprayed old Concord vines 20 23. 6 
Unsprayed Niagara vines 35 56.0 
Sprayed Niagara vines Free. 1.2 
The Porter vineyard, located a few miles east of the town and con- 
taining 10 acres of old Concord vines, gave the following results: 
Unsprayed plat had 14.7 per cent parasitized eggs. 
Sprayed plat had 5.5 per cent parasitized eggs. 
By comparing the records taken during August from three different 
vineyards located within a radius of from 2 to 3 miles east of N rth 
East, Pa., Algren's vineyard on August 4 showed 2 per cent of para- 
sitized eggs; Young's vineyard, August 24, showed 16 per cent; and 
Wheeler's vineyard, August 27, 96 per cent. 
A marked increase of parasitism was observed with the advance- 
ment of the season. The records given below, obtained by H. B. 
Weiss, from Mr. Young's vineyard, illustrate this fact: 
Per cent. 
July 30 5 
August 13 10 
August 19 14 
August 26 16 
September 2 20 
Similar records from other vineyards were not as uniform as those 
just given, but since the percentage varies with the amount of eggs 
present, no great uniformity can be expected unless the eggs are found 
more or less evenly distributed in the vineyards. 
By breeding the parasites two full generations and a partial third 
were produced. Infested eggs were obtained in the field July 13, from 
which adults emerged August 3. These were placed with fresh eggs 
August 4, and new adults issued August 28. The third generation 
developing from these adults was much delayed by cold weather, but 
at the time of concluding the field work for the season on November 
22 the adults were about to emerge. 
