. Annual report. Entomological Society of Ontario; Insect pests; Insects. 42 THE REPORT OF THE population very rapidly. In order to condense the figures gathered during four years of investigation on this subject, it was necessarv to tabulate the mean population in the counts for the years 1933-34-35-36. The popula- tion of aphids in 1933 began to increase on July 4 and kept increasing until it reached its maximum on about July 24. In 1934, the population was much higher than that of 1933 and reached its maximum on Julv 25 to drop suddenly towards the end of the month. In 1935, the type of inf
. Annual report. Entomological Society of Ontario; Insect pests; Insects. 42 THE REPORT OF THE population very rapidly. In order to condense the figures gathered during four years of investigation on this subject, it was necessarv to tabulate the mean population in the counts for the years 1933-34-35-36. The popula- tion of aphids in 1933 began to increase on July 4 and kept increasing until it reached its maximum on about July 24. In 1934, the population was much higher than that of 1933 and reached its maximum on Julv 25 to drop suddenly towards the end of the month. In 1935, the type of infesta- tion was entirely different to that of the two previous years. From July 2 until July 11, the population increased gradually to decrease rapidly after- wards until the end of the £ 17 18 19 26 Zl 21 23 Z* IS 26 Z7 28 2? JO Fig. 1.—Diagram showing the average number of aphids counted on different dates from all samples of the varieties studied. - It was interesting to observe that in 1935, although the population was much lower than that of 1933 and 1934, the injury caused to the peas was rather severe. This was due to the rapidity with which aphids mul- tiplied during the first part of Juh^. During the two first years (1933-34) the maximum infestation was quite late and there was no real danger for the pea crop, but in 1935 the greatest amount of aphids appeared when the plants were forming their pods, exactly at the period of growth the peas are most susceptible to serious injury with even a lesser degree of infestation. With regard to the infestation of 1936, very little damage was done to the crop. The average population was rather low throughout the period of infestation. We attribute this to a relatively cool rainy season. Relation Bettveen Varieties and Average Number of Aphids.—Table 2 and figure 2 show the relation that exists between varities and the degree of infestation during the period that extends from the first appearance of aphids to the time
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