304 The Ecologic Relations of the Photogenic Function among Insects. 



Osten-Sacken's work at the time, Mcüermott (11) recorded 

 observatious on the niating of Photinus pyralis verj similar to Ihose of 

 Osten-Sacken. He found furlher that it was possible to cause light- 

 emission from either sex by the proper Operation of a small electric 

 lamp in imitation of the opposit sex, or from the females by flashes of 

 light from other sources, such as a match. A slight pause was fouud 

 to interveue between the flash of the male and the answering flash of 

 the female. McDermott (11, 12) extended his observations to P/io/m?fs 

 consanguinens, P. scintillans, P. margineUus, P. castus and Lecontea 

 lucifera. 



In Photinus consanguineus the flash of the male, instead of beiug 

 Single, is composed of two distinct coruscations, while that of the female 

 is a Single flash like that of the female j;»/ra/?s; the fema\e consangtiineus 

 would answer onlj to a double flash. In P. scintillans and P. castus, 

 both smaller species than P. pyralis, the flashes of the male and female 

 are both single, and of rather shorter duration than that of pyralis; 

 the ranges of the two species appear to overlap, though they were not 

 fOLind together. P. castus and P. marginellus were found in the same 

 babitat; the mauner of light-emission of the males of the two species 

 differs ouly slightly, that of marginellus being a trifle sharper. The fe- 

 males, however, appear to distinguish between them readily, and the 

 answering flashes of the two feinales are quite different. The flash of 

 the female castus is a single flash, as described above, foUowing the 

 flash of the male by a very short pause; that of the female marginellus 

 is a distinctly double flash, the two maxima foUowing each other clo- 

 sely. With the idea of making these differences somewhat clearer, the; 

 accompauying diagram has been drawn, in which the abcissae represent 

 time, one second to the centimeter, while the ordinates represent lumi- 

 nous inteusity, one centimeter equalling approximately 0.02 candle- 

 power. 



Photinus castus was first described by Leconte as a separate species, ', 

 but was later classed by him as a variety of marginellus. On account i, 

 of the differences in light-emission, McDermott (13) has restored itj 

 to the Position of a distinct species. 



Green (6) has recently described the msLÜng oi Dioptoma adamsii; 

 In this species the luminous organ of the female is, as usual, ventral, 

 but the Juminosity is rendered more affective by curling the abdomen 

 over the dorsal, so as to expose the surface of the luminous apparatus 

 upwards. The abdomen is returned to the normal position upon the 

 approach of the male. In this case, as in Lampyris noctiluca, the fe- 

 male is larger and brighter than the male. 



The conduct of the Lampyridae toward artificial light is of interest. 

 Both McDermott (11, 12) and Mast (10) have shown that the species 

 of Photinus may be deceived by small artificial lights operated in imi- 

 tation of the opposit sex. They are, however, practically unaffected by 

 ordinary continuous lights. The writer has seen a male Photinus pyralis ■■ 

 fly past an open arc-light, within about 1.25 meter of the are, without 

 showinK the least siij;n of attraction toward it. On one occasion a de- 

 cided attraction toward an oil lamp was observed on the part ot a male 

 of Lecontea lucifera. Lund (8) has observed that the Jamaican species 

 Photinus pallens shows a very slight attraction toward ordinary lights, 

 On the other band, the males of Lampyris noctiluca have long been 



