24 THE PERIODICAL CICADA. 
being temporary, this portion of the old brood resumed the normal 
13-year period. 
Another marked instance of the same kind is shown in the relations 
between Brood XI and Brood X, the former being merely an appen- 
dix or a continuation in a northeasterly direction of the territory occu- 
pied by the eastern branch of Brood X, which always precedes Brood 
XI by one year. The interrelations of these and all the other broods 
are indicated in the discussion of the distribution of the Cicada. 
Local or temporary conditions which have caused a moderate 
change in the time of emergence of the Cicada are on record, one 
notable instance resulting from an artificial heating of the soil by hot 
pipes (see p. 90). . 
A similar instance of acceleration of Brood XIII, due in 1905, but 
amounting to a full year, occurred in 1904 in a greenhouse at Belvidere, 
Ill. The owner, Mr. B. Eldredge, writes that in 1888 he moved from 
Chicago to Belvidere, and found everything covered with locusts, 
and an enormous amount of damage to all kinds of shrubs and trees 
wasdone. At the time he bought the place it was covered with an old 
apple orchard, and the locusts worked very abundantly in these trees. 
Some seven years afterwards these trees were grubbed out and the 
ground covered with greenhouses, and the ground so protected had 
been kept warm winter and summer ever since. Mr. Eldredge is 
convinced, and he is undoubtedly right in this belief, that this con- 
tinual heat and absence of frost accounts for the appearance of the 
locusts in his greenhouses a year ahead of time. 
He states that the locusts appeared in quantity. Before the mat- 
ter was brought to the writer’s attention they had largely disappeared, 
but two adult locusts were submitted and a lot of shed skins, which 
fully confirmed the identification of the insect. It would be rather 
interesting to know more about the local conditions to determine how 
the cicadas were able to survive in soil from which the vegetation 
must have been entirely removed. 
An instance of a few weeks acceleration under outdoor conditions 
is given by Mr. Schwarz.¢ Commenting on the shghtly earlier emer- 
gence of individuals of Brood XIV near Harpers Ferry, W. Va., in 
1889, in a small clearing surrounded by woods, Mr. Schwarz urges 
that a clearing made in the midst of a dense forest forms a natural 
hothouse, the soil receiving in such places much more warmth than 
in the shady woods. That the cicadas should appear a little earlier 
in such situations is not remarkable, and he suggests also that under 
favorable circumstances the Cicada might develop on such cleared 
places one or more years in advance of the normal time, and that 
these precursors, if numerous enough, would be able to form a new 
brood. 
a Proc. Ent. Soc. Wash., I, p. 230. 
