382 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1919. 
Marlatt in his report, "The Periodical Cicada,"' Bulletin 71, United 
States Bureau of Entomology, published in 1907. Doctor Marlatt de- 
scribes six immature stages between the egg and the adult, the first 
four of which are distinguished as larval stages and the last two as 
pupal. But this does not mean that the " pupa " of the cicada is a 
resting stage like that of the moth or butterfly. The cicada pupa 
(pi. 1) is an active creature like the larva (fig. 9), differing princi- 
pally in having short wing pads. The first pupal stage begins in 
about the twelfth year of the insect's life. 
In the spring of their seventeenth year the cicadas burrow upward 
througli the soil till they come to wuthin a few inches of the surface. 
Eecorded observations indicate that this migration takes place dur- 
ing the month of April. We know that the insects leave the earth 
during the latter part of May, so it seems that they must gather 
just below the surface and there await for several weeks the proper 
time for their emergence. Then, all of a sudden, as if at a giA'^en 
signal, the mass of them issues in swarms every evening for several 
days, and the ground is perforated with their exit holes. 
It is with a feeling akin to awe that we witness for the first time 
vast numbers of these insects issuing from the earth. Then we realize 
that they have all been quietly living beneath our feet these many 
years where we gave no thought to them. Each exit hole now be- 
comes a dividing point for us between knowledge and ignorance — 
the history of the insects after reaching the surface is so easy to read, 
that before so difficult. What secrets have they left behind in those 
narrow tunnels? 
The original notes on which this paper is based were made during 
the season of 1919 at Somerset, Maryland, where, through the 
courtesy of Dr. E, F. Phillips, the writer had use of a room in the 
house of the Office of Apiculture, United States Bureau of Ento- 
mology. Dr. Phillips also entered into a part of the work, especially 
that of studying the burrows, and the emergence and transformation. 
One evening it occurred to us that something might be learned 
simply by pouring a water solution of plaster of Paris into the bur- 
rows. Accordingly, we filled a few at first, but many swallowed up 
so much of the liquid that we became hopeful of a real discover}^ and 
eventually filled a score or so and allowed the plaster to set over 
night. The drawings on figure 1 show a part of the results revealed 
on the next and several subsequent days as we unearthed the hard- 
ened casts. Each represents the outline of a subterranean chamber 
in which the pupa had been concealed, waiting the proper time for 
its emergence. The longest chamber reached to a depth of 6 inches, 
the shortest are mere cups. All have a more or less distinct enlarge- 
ment at the bottom, and most of them a swelling at the top just be- 
neath the narrow neck, which represents the emergence hole. In all 
