384 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1919. 
but one the shaft has a diameter of about five-eighths of an inch, 
while that of the basal enlargement is seven-eighths of an inch. The 
neck averages about half an inch across. One cast is smaller, having 
the neck three-eighths of an inch in diameter, the shaft one-half, the 
lower sTfelling eleven-sixteenths. The individual that made this 
tube was most probably a pupa of the smaller form of the cicada, 
which will be described later in connection with the life of the 
adults. 
The chambers are seldom straight, their courses being more or less 
tortuous and inclined to the surface, as the miner had to avoid roots 
and stones obstructing the path. The interior contains no debris of 
any sort, and the walls are smooth and compact. The largest cham- 
bers are many times the bulk of the pupa in volume, and the insect 
can easily turn around in them, though it can not quite sit cross- 
ways on the floor of the lower enlargement. Belov/ the chamloer 
there is ahvays evidence of a narrower burrow going irregularly 
down into the ground, but this shaft is filled to the chamber floor 
with black granular earth. The burrows examined at Somerset 
were dug through compact red clay, so the filling of the lower tubes 
Avas probably discolored by the admixture of fecal matter. For this 
reason these tunnels always made a distinct black path through the 
red of the surrounding clay and could often be followed a consider- 
able distance. 
Before the emergence of the pupa the chambers are closed at the 
top by a cap of earth a quarter or a half inch in thickness, and this 
cap is the original earth surface. Where, then, is the material that 
was excavated in the construction of a hole of such size? Was it 
carried down into the tunnel beneath the lower rotunda ? This tun- 
nel is always much narrower than the diameter of the chamber and 
it would take a long section of its length to hold the excavations 
from the latter. Moreover, if the debris from the chamber was 
dumped into the hole below, what was done with the original con- 
tents of this cavity? Explaining one mystery by postulating an- 
other does not explain anything. As long as we have a hole to 
account for, we might as well account for the one we are sure of, 
and the best way to begin is by giving the insects themselves a chance 
to reveal their secrets. 
Drop several pupae into glass tubes, fill the tubes with loose earth 
and watch the performance. Those pupae observed thus by the 
writer gave a very clear exhibition of their methods of work, which 
probably explains how they accomplish the seemingly impossible 
feat of digging a hole without throwing out any earth. They demon- 
strated first that they do not burrow by plowing through the earth 
with the conical nosepiece that caps their faces, though the earth in 
