THE CANADIAN ENTOMOLOGIST. 309 



OBSERVATIONS ON THE LIGHT-EMISSION OF AMERICAN 

 LAMPYRID^.— Fourth Paper. 



BY F. ALEX. MCDERMOTT, PITTSBURG, PA. 



In continuation of his former observations on the light-emission of 

 American Lampyridae and its relation to the sexual life of the insects 

 (Can. Ent., 1910, Vol. 42, pp. 357-363; 191 1» ^o^- 43. PP- 399-4o6; 

 191 2, Vol. 44, p. 73), the writer has made during 191 2 the observations 

 recorded below on species of Lampyridae not heretofore encountered by 

 him, which support his former observations and show specific distinctions 

 which are of interest. About the time of the publication of the second 

 paper of this series, Dr. S. O. Mast, of Johns Hopkins University, read the 

 a paper embracing very similar observations on (probably) Photinus ardefis 

 Lee. and emphasizing the bearing of the behaviour of these insects on the 

 theory of phototactic orientation (Abstract in Science, 191 2, Vol. 35, 

 p. 460.) 



Photinus marginellus Lee. — This species was first observed in Ash- 

 land, Ohio, during the latter part of June. In the late afternoon, several 

 hours before sunset, both sexes were found in flight and resting on the 

 leaves of low plants. As mentioned by Leconte, the male greatly resembles 

 P. scintilla7is while the female, instead of being apterous as in the latter 

 species, has wings and elytra as fully developed as those of the male. The 

 flash of the male is a single, short, sharp one, and in colour appears 

 to the eye more yellowish than that oî sciniillans, though resembling that 

 of the male of the latter species in intensity and manner of delivery. The 

 flash of the female marginellus, however, differs distinctly from that of the 

 female scintillans; instead of being a single flash, somewhat slower than 

 that of the male, as in scintillans, the flash of the female fnarginellus con- 

 sists of two coruscations, the first being brighter and of shorter duration 

 than the second, which follows the first immediately. The flash of the 

 female is delivered with only a very^short interval after the flash of the 

 male she is answering. It will be noticed that this double flash of the fe- 

 male fnarginellus differs decidedly from the double flash of the male of 

 P. consanguineus previously described. 



Photinus castus^ Lee. — This species was found during June and July 

 in open places, particularly in Schenley Park in Pittsburg, Pa. 



*See following footnote. 



October, 1912 



