100 
THE PERIODICAL CICADA. 
trunks was (iuite audible, particularly vigorous pupie ascending the trees to the 
height of 30 feet. 
l^lato X, sliowing einpt}^ pupal shells clinging to leaves, still further 
illustrates the large number of these msects which often emerge. 
As noted ])y Mr. Farinsley, of Louisville, Ky., the cicadas do not 
appear very numerously on tops of mountains within an infested area, 
})ut gradually decrease in numbers as one ascends, the greater scarcity 
l)eing noticeable both to the eye and the ear, the rattling chonis 
growing less and less strong. 
On the authority of Dr. Hopkins, the dinunishing of the Cicada in 
numbers as one ascends to higher elevations is apparently not always 
true. Dr. Hopkins describes driving for a day through theCicachi 
district of AYest Virginia in 1897 on the occasion of the reappearance 
of the 17-year Brood V, and states that as he approached the eastern 
e V « 
^ 9 
•9 - - . V r - - 
• ♦^ 
. ff' 
/'•.• 
<>.- *- 
• - V 
>\^.:i 
Fig. -10.— Exit holes of the periodical Cicada at surface of soil. The rule shows the large number of 
holes occurring, in this instance, in a square foot of ground 
borders of Preston County the cicadas became more numerous, 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 an}^ point previously traversed. The leaves and 
t\vigs of the trees were literally covered ^^ith 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 
l^ecame xery 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, 
arc irregular in local distribution. This variation in abundance is 
due in some cases to difl'erences in the character of the soil and in 
others, perhaps, to varying surface conditions, as of timber growth, 
etc. They j)refer, apparently, white-oak groves, and are most abun- 
