386 ANNUAL EBPORT SMITHSONIAN INSTITUTION, 1919. 
back is firmly pressed against the opposite side of the growing cavity, 
the middle femora are bent forward till their knees are almost 
against the bases of the front legs, their tibiae lying along the wing 
pads. The hind legs assume a normal position, though held close 
against the sides of the body. 
Thus, the secret is out, the cicada excavates a closed cavity by 
crowding the earth back into the surrounding earth. What a slow 
and laborious task the construction of one of the larger chambers 
must be to the insect working within ! Imagine a person making a 
cave of proportional dimensions in such a manner. No records are 
at hand to show when the cicada begins its work or how long it takes 
to finish the task. Those that performed in the tulles never emerged. 
But they had already left their original chambers and their time 
was ripe for transformation. Their skins split in the midst of their 
labors. 
From what we know of the cicada's spring habits underground, we 
can infer that the pupae construct their chambers on their arrival 
near the surface during April, that, when the chambers are completed, 
the insects await within for the signal that it is time to emerge and 
transform into the adult. Then they break through the thin caps 
at the surface and come out. It would be difficult to explain how 
they know when they are so near the top of the ground, and why 
some construct ample chambers several inches deep, while others 
make mere cells scarcely larger than their bodies. Do they burrow 
upward till the pressure tells them that the surface is only a quarter 
of an inch or so away, and then widen the debris-filled tunnel down- 
ward? Evidently not, because the chamber walls are made of clean, 
compacted clay in which there is no admixture of the blackened con- 
tents of the burrows. It is unlikely, too, that they base their judg- 
ments 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. But time is only wasted in trying to reason 
out the acts of any insect. The insect is almost sure to have ways of 
its own that our reason seldom hits upon. 
An interesting feature in the development, described by Doctor 
Marlatt, is the change that takes place in the size of the front feet. 
The young larvae, which hatch from the eggs in the trees, have well 
developed front tarsi. (Fig. 9.) In the succeeding three larval 
stages each front tarsus is reduced to a mere spur on the inner face 
of the tibia. Finally, in the pupal stages, the tarsi reappear as well- 
developed feet. Both the larva in the first stage and the pupa in the 
last stage spend a part of their lives on the trees, and to them the 
front tarsal claws are important climbing instruments; but in its 
other stages the creature lives entirely underground, where it digs 
