NSECTS
is no admixture of the blackened contents of the burrows. It is unlikely, too, that they base their judgments on a sense of temperature, because their acts are not regulated by the nature of the season, which, if early or late, would fool them in their calculations. Early in the spring, before the proper emergence season, cicada nymphs are often round beneath logs and stones. This is to be expected, for, to the ascending insect, some- thing impenetrable has blocked the way, and there is nothing to tell it that it has already reached the level of the surface. A more curious thing, often observed in some localities,
F1G. i17. Earthcn turrcts somctimes. erected by the nymphs of the period?cal cicada as continuations from their under- ground chambers. One cut open showing the tubular cavity within. (From photo- graph by Marlatt)
is that the insects some- rimes continue their chambers up above the surface of the ground within closed turrets of mud from two to several inches in height (Fig. 117). At certain places these cicada "huts" have been reported as occur- ring m great numbers; and it bas been supposed that they ma}" be built wherever there is some- thing about the nature of the soli that the insects do not like, the earth being perhaps too damp, for they are frequently round where the ground
is unusually wet. On the other hand, the turrets have been observed in dry situations as well, and towers and holes flush with the surface frequently occur intermingled. The writer has had no opportunity of studying the cicada turrets, but a most interesting description of them is given [Igal
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