36 



No male was ever observed to reply to the flash of a 

 creeping male. 

 P. coman<inineiis. — The male gives a double flash, two flashes in 

 quick succession followed by a pause, then two more, and so 

 on ; the female replies within a second to the second flash of 

 the male. . 



A particular female would not reply to the flash of a 

 match, but would answer the double flash of a bulb when 

 twenty or thirty feet away ; on a nearer approach she seemed 

 to recognise something unusual and would no longer reply. 

 P. scintillan.s. — The male gives a short single flash and the female 

 a longer single flash ; the female in this species is apterous. 

 A female would reply to the first flash of a male of P. 

 consanfiicineini, but the latter takes no notice. 

 P. )»ar<iinellt(s. — The male eives a single short sharp flash, 

 yellower than that of P. ficintillaiis ; the female replies with 

 a double flash, the first sharper and brighter than the second, 

 followed at once by the second. The reply is given very 

 quickly after the flash of the male. 

 P. castas.- — The male gives a single flash, not so short and sudden 

 as that of P. iiiar/iinellHti ; the female gives a single flash 

 very much like that of P. sciutillana, but delivered immedi- 

 ately after the flash of the male ; there is no distinct pause 

 as in P. pijralis, and no indication of doubling as in P. 

 marginelliis. 



P. castas and P. marfiinellns are very similar, and indeed 



by some authorities have been considered to be merely forms 



of one species. Mr. McDermott admits that he can find no 



points of structural diflerence between them, but considers 



them distinct species on account of the very different flashes 



emitted by them. They are frequently found flying together, 



but no case of interbreeding has been observed, though 



especially watched for. 



In connection with these lightning-bugs a brief experience of my 



own may be of interest, but since at the time I had no intention of 



writing this paper I failed to make as good use of the opportunity 



for observing them as I could now wish to have done. Two years 



ago I paid a short visit to the United States, and for the first time 



met any of these winged and flashing glow-worms, and the sight of 



them in their thousands sparkling in the woods and meadows made 



an impression on me that can never be erased. Not knowing at the 



time of McDermott's work on them I thought I would investigate 



the functions of the light in the courtship of the sexes, but beyond 



finding that they all appeared to be males I could make nothing out 



of them ; each beetle was visible merely as a succession of sharp 



flashes, and the emission of the light was apparently quite aimless. 



In the course of a visit to Washington I mentioned my fruitless 



efforts to Mr. H. S. Barber, of the National Museum, and he told 



