28 THE PERIODICAL CICADA. 
illustrates the new nomenclature suggested, and in parallel columns 
also are given the corresponding nomenclatures proposed by Professor 
Riley, by Fitch, and the year records in Doctor Smith’s register: 
Nomenclature of the broods of the periodical Cicada. 
Broods of the 17-year race. Broods of the 13-year race. 
Year. Proposed| Riley Fitch | Smith | Proposed] Riley Fitch Smitt 
enumer-| num- num- | regis- | enumer-| num- | num- saa fa 
ation. | bers. bers. | ter. ation. bers. bers. | register. 
0 ee eee ae eee eee I pain: © Oe ain (ee 3 aoe 1842 | XVIII SVE eeaeees 1854 
sey ee Se cme oes ae Il XII 1 1843 XIX | XVIII 3 | 1842-1855 
1SORo Matis oe oe Cen, TET Po] = NCTA Toon | eae eee 1844 | 1843 
SOG sos 22 ae Ss OS: nese IV STV spall he Ae 1845 1844 
INS ps Maia eS ae V SOY 5 | 1846 | 1845 
LSOR FSA eek eee Seek VI SOVIET) 7 | 1847 | 1846-1859 
SOON me ey eee em rae meas Vil DS Dae | ee ee 1848.) SXORMW eos 
1900 ee 5. Satya te Seek VTE Tees |W ERERE D975 2=83 (11849 lite seas 
OQ ae See pee slater IX OR eas See 1850 1849 
HOO 2240. ¢ Seek yi ee ae x XXII Alle LSS lls SEARO W LAD | Fe ar Se aed | 
NGO Soesaee ea Seek ene Sell I 9 1352) | EXSOV TE ee oe 2c eee eel eee 
O04 2 See ae ee yao ee ROT tee ce ene, See ee 1853 ees See 
O05 ee fins Jae eee XU \ 6 | 1854 Nes ean So 
(Q0G=4- 2 ee ee ee sae XIV VIII 1855 1854 
OO (eee cars Jase seeesiosee VE Se rete cay est erm | eee 1842-1855 
19085 427205 2 Me eae xvi aU RN reese Pieris eae 1843 
O09 Bare. soe caligene coc eee SREY TEL B\'- art eoee eeey| se, 2, em eee ee 1844 
THe RELATIONSHIP OF THE DIFFERENT Broops. 
As a rule, the relationship of the broods in point of distribution 
agrees with their kinship as indicated by their sequence in time of 
appearance. The relationship indicated by the latter, viz, their 
sequence in time, is doubtless untrustworthy as indicating origin, in 
some instances on account of the uncertainty arising from the action 
of the principle of retardation on the one hand and acceleration on 
the other in the forming of new broods. 
In the case of a widely scattered brood, like Brood VI, it is quite 
possible that certain swarms originated from a later-appearing brood 
by retardation of individuals, and other swarms from an earlier 
brood by acceleration in time of appearance of individuals.¢ 
This same condition may be true of other of the more scattered 
broods, but with the broods presenting a compact range a singleness 
of origin is evident. 
Examination of the distribution of the broods in connection with 
their sequence in time of appearance indicates, however, a certain 
a Prof. W. E. Castle, Museum of Comparative Zoology, Cambridge, Mass., in a letter 
to the writer July 20, 1898, suggested a plausible theory for Brood VI. The isolation 
and wide distribution of this brood leads him to infer that it may be a relatively old 
or “played out’’ brood, and if this be true it may be considered the parent of Broods 
V and VII, the former an offshoot by acceleration and the latter by retardation of 
development. He suggests, however, that the Pennsylvania portion of Brood VII 
may have originated independently of the New York part, since it lies in the moun- 
tainous country, where the broods would naturally be mixed up more than in any 
other part of the range of the 17-year race. In Ohio he notes that the distinct areas 
