. Bulletin. Insects; Insect pests; Entomology; Insects; Insect pests; Entomology. 100 THE PERIODICAL CICADA, trunks was quite audible, particularly vigorous pupa,' ascending the trees to the height of 30 feet. Plate V, showing empty pupal shells clinging to leaves, still further illustrates the large number of these insects which often emerge. As noted by Mr. Farmsley, of Louisville, "Ky., the cicadas do not appear very numerously on tops of mountains within an infested area, but gradually decrease in numbers as one ascends, the greater scarcity being noticeable both to the eye and the ea
. Bulletin. Insects; Insect pests; Entomology; Insects; Insect pests; Entomology. 100 THE PERIODICAL CICADA, trunks was quite audible, particularly vigorous pupa,' ascending the trees to the height of 30 feet. Plate V, showing empty pupal shells clinging to leaves, still further illustrates the large number of these insects which often emerge. As noted by Mr. Farmsley, of Louisville, "Ky., the cicadas do not appear very numerously on tops of mountains within an infested area, but gradually decrease in numbers as one ascends, the greater scarcity being noticeable both to the eye and the ear, the rattling chorus growing less and less strong. On the authority of Dr. Hopkins, the diminishing of the Cicada in numbers as one ascends to higher elevations is apparently not alwavs true. Dr. Hopkins describes driving for a day through the Cicada district of West Virginia in 1897 on the occasion of the reappearance of the 17-year Brood V, and states that as he approached the eastern. Fig. 40.—Exit holes of the periodical Cicada at surface of soil. The rule shows the large ;iunil)er o. holes occurring, in this instance, in a square foot of ground borders of Preston County the cicadas became more niuuerous, and as the mountain west of Cranesville was ascended the Cicada was found, at an elevation of 2,600 to 2,800 feet, to occur in far greater numbers than at any point previously traversed. The leaves and twigs of the trees were literally covered with the insects, and the twigs were bending from their weight. This point seems to have been the eastern border of the swarm, and a few rods farther up the cicadas became very scattered and soon ceased altogether. They often also appear in greatest number in rather well-defined districts within the general range of the brood, or, in other words, are irregular in local distribution. This variation in abundance is due in some cases to differences in the character of the soil and in others, perhaps, to varying surface conditions, a
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