DECEMBER 6, 1918] 
lege, the maintenance of which is one of the 
lines of activity of the Rockefeller Founda- 
tion. 
DISCUSSION AND CORRESPONDENCE 
CONCERTED FLASHING OF FIREFLIES 
On a hot and dark evening in the summer of 
1915, a camping party sought the rocks near 
the waters edge on the north shore of Sloop 
Bay, Valcour Island, Lake Champlain. An 
intermittent flashing of diffused light was 
soon noticed in the northwestern corner of the 
bay between 300 and 350 meters distant. This 
flashing was somewhat similar to that ordin- 
arily called “heat-lightning,” but as it ap- 
peared against the base of a_ cliff something 
over ten meters high an investigation of the 
phenomenon was decided upon. 
On approaching in canoes, a scene of won- 
drous beauty presented itself. The light was 
due to the minature lamps of several thou- 
sands of fireflies which were holding festival 
over what appeared to be a breeding ground. 
The area involved was about 100 meters in 
length and extended from near the water’s 
surface to a height of about seven meters. 
At this locality the bare rock faultscarp which 
formed a portion of the north wall of the bay 
was covered with a steep sloping bank of 
glacial and postglacial deposits and these were 
well supplied with water through seepage. 
Moving southwesterly one left the bare por- 
tions of the cliff and rapidly passed through 
various plant communities from lichens and 
mosses to a small grove of white pines. Above 
this locality there was also a forest clearing 
used as a meadow. 
At no time over the limited area at the base 
of the bank could one notice an utter absence 
of illumination but the lighting of a small 
cluster of lamps seemed to awaken immediate 
response from a thousand others, and the illu- 
minated area thus spread from one or more 
centers until the bank was brilliantly ablaze 
and suggestive of the myriad lights of some 
city of fairyland. It was these periods of in- 
tense illumination that had attracted the at- 
tention of the camping party at a distance so 
great that the lights from a few scattered 
SCIENCE 
573 
lamps seemed to leave the bank in absolute 
darkness. The same phenomenon was also ob- 
served on the following evening. 
After reading Dr. Edward S. Morse’s “ Fire- 
flies Flashing in Unison”! the writer deter- 
mined to make another visit to this locality 
and observe the phenomena more critically. 
On the evenings of July 11 and 12, 1916. the 
display was repeated and observed by several 
visitors. It was impossible to count the num- 
ber of lamps which were aglow at one time, 
but the space involved was about 700 square 
meters in cross section and in some bush- 
covered places there must have been at least 
50 fireflies to the square meter. We should 
judge that about 10,000 of these insects were 
present. During these visits we noted that 
the illumination was never due to a truly syn- 
chronous lighting of the lamps of those fire- 
flies engaged in the display but was always 
of the nature of wave motion spreading out 
from one or more centers. This spreading 
moved swiftly from one end of the bank to 
the other and was particularly beautiful when 
the light from several centers became con- 
fluent, for at that instant the whole bank was 
very brilliantly illuminated. Strictly speaking 
there was no measured regularity in this con- 
certed response and therefore no true rhythm, 
—such as one may note in the concerted music 
of certain orthoptera. The repititions were 
hardly more regular than the cloud illumina- 
tions of a distant thunderstorm. There was 
present the influence of suggestion on what 
may be called a “mob-psychology ” but there 
was no special leader. Any small group could 
excite a discharge from thousands who were 
ready to respond. As recovery was rapid, the 
repititions of the wave-like responses were also 
rapid. 
It is probable that the phenomenon is by no 
means a rare one and that, in this locality, it 
is repeated yearly—though the display of 1916 
was not quite so brilliant as that of 1915. A 
display in any place would be compellingly 
attractive to a passing person only if the 
festival period occurred during very dark, 
cloudy or moonless nights. The observer 
1 SorenceE, February 4, 1916. 
