42 WALTER N. HESS. 



female the organ occupies only a small area on the sixth abdominal 

 segment. They measure from 8 to 12.5 mm. 



LeConte reports them from Massachusetts, Pennsylvania 

 and Virginia. Blatchley lists them for Indiana, and Williams 

 found them abundant in Massachusetts. 



The biology of this species has been well described by Williams 

 (1917), so an attempt will be made here to discuss only a few of 

 the more important features. 



The adults begin to emerge about June I and can be found 

 along moist areas until about the first of August. They are 

 frequently found in association with Photinus scintillans and 

 Photurus pennsylvanica. The males are active fliers, and though 

 the females have well developed wings they were never found in 

 flight. The flight of the males begins about 8:15 P.M. and 

 continues until about 10:00 P.M. (old time). The light of the 

 male is a single bright flash, though at times he emits two or 

 three flashes in rather close succession, but in every case there is a 

 considerable interval between each flash. The female of this 

 species crawls up a stem of grass, or some similar object, and 

 emits a faint flash in response to the flash of the male. Just 

 before emitting the light, however, she turns her abdomen so 

 that the ventral side is in the direction of the male, thus in part, 

 at least, obviating the necessity for larger light-organs. 



What was discribed as the synchronous flashing of fireflies 

 was first discussed by Blair (1915), who reported observing 

 fireflies, in a certain locality, flashing in unison. Later his 

 observations were confirmed by other writers. Morse (1916) 

 reported an observation in which the light emitted by these 

 little creatures pulsated in a regular synchronous rhythm, so 

 that at one moment the tree, about which they were flying, 

 would be one blaze of light, while at another the light was dim 

 and uncertain. 



According to Blair (1915) and McDermott (1916), this phe- 

 nomenon does not occur among the American species of Photinus 

 and Photurus. The writer, however, observed the flashing of 

 fireflies in unison on two very dark evenings during the present 

 summer while collecting eggs and larvae at Ithaca, New York. 

 Toward the south side of the City Cemetery is a small valley, 



