PERIOD OF EMERGENCE. 89 
Doctor Phares, writing of the occurrence of Brood XXII in 1871, 
states that a few males began to appear about the 20th of April, but 
that the bulk of the brood did not emerge until the 7th and Sth of 
May, when they came forth from the earth in vast numbers, continu- 
ing to emerge in diminishing numbers until the 18th of May. It will 
be remembered that this is the most southern of all the broods—lying 
in the southwest corner of Mississippi and the adjoining parts of 
Louisiana. 
Mr. John Bartram, writing of the brood appearing in 1749, states 
that in the neighborhood of Philadelphia an abundance of these 
insects which had just escaped from their skins was observed on the 
morning of May 10 and that they continued to issue in great numbers 
for a week or more, beginning to sing on the 13th and to oviposit on 
the 16th, and disappearing altogether by the Sth of June. 
In the great brood year of 1868 Professor Riley noted that in the 
vicinity of St. Louis “they commenced to issue on the 22d of May, 
and by the 25th of the same month the woods resounded with the 
rattling concourse of perfect insects.’”’ At Washington, D. C., in the 
Cicada year 1885, scattered individuals appeared on May 23, and they 
issued, perhaps, most abundantly on the night of the 27th. Those 
emerging within the city were somewhat earlier in appearance than 
was the case in the neighboring woods across the Potomac in Virginia, 
probably for the same reason that the trees in the city put out their 
foliage a little earlier than in the near-by woods. 
Mr. Davis, writing of Brood II as it appeared in 1894 on Staten 
Island, New York, says that as early as May 19 many cicadas had 
emerged, the first individuals of the swarm being noted six or seven 
days earlier. 
Mr. A. W. Butler, writing of the brood appearing in 1885 in Frank- 
lin County, Ind., says that while in a few localities individuals were 
seen as early as May 28, in other places not distant they did not 
emerge until June 4, and later. 
Mr. Hopkins made a careful study of the dates of emergence in West 
Virginia in 1897 in connection with Brood V, and found very consid- 
erable variation in time of appearance both between the northern and 
southern borders of the brood and between the lowest and highest ele- 
vations within the area covered by the brood. For the former a differ- 
ence of nearly two weeks was indicated by the records, and for the 
latter a difference of nearly four weeks. This variation, he says, 
appears to be due to the difference of climate between the northern 
and southern sections and between low and high elevations, in the 
former case amounting to 34 degrees and in the latter to over 10 
degrees in average summer temperature. He deduces from his obser- 
vations, as a general rule, that there is about three and one-half days 
difference in the time of the first general appearance of the Cicada for 
