238 THE CANADIAN ENTOMOLOGIST. 



OBSERVATIONS ON LAMPYRIDtE. 



BY FREDERICK KNAB, URBANA, ILL, 



Two species of fire-flies are abundant in western Massachusetts in 

 the early summgr and often their display of light presents a magnificent 

 spectacle. These species are Phothius scintillans^ Say, and Photuris 

 Pe?ifisylvanica, De Geer. Photinus scmtillans becomes active very early 

 in the evening, and long before twilight begins its orange-coloured light 

 may be seen flashing among the shrubbery. It is only active during the 

 twilight hour and some time before total darkness has set in its lights have 

 disappeared. This species frequents localities with abundant shrubbery, 

 and often congregates in certain copses or on the margin of the woods, 

 while other similar situations are almost deserted. Even in larger towns, 

 where there are gardens with shrubbery, it may often be seen in some 

 numbers. 



The other species, Photia-is Pennsylvanica, is the most abundant of 

 all the fire-flies. It makes its appearance in the late twilight and its dis- 

 play of light continues far into the night. Its light is more brilliant than 

 that of the first mentioned species and of a distinctly greenish colour. 

 This species is partial to low, moist situations, and is particularly abundant 

 on low meado'.vs bordering rivers. In the time of their greatest activity, 

 when thousands are sending forth intermittent flashes, they ofi'er a spec- 

 tacle beautiful beyond description. 



It occurred to the writer that the difference in the colour of light of 



these two species of fire-flies might possibly be one of optical effect, rather 



than an actual diff'erence. While the light of Photinus sclntillans appeared 



bright orange and that of Photuris Pennsylvajiica a pronounced green, no 



comparison could be made, for the two forms do not display their light at 



the same time and place. Perhaps the light of Photinus scintillans 



appeared orange simply in contrast with the bright green of the vegetation, 



still plainly visible at the time of the beetle's appearance, and, indeed, 



then of a more pronounced colour than under the strong light of full day. 



This supposition was strengthened by the fact that when one of these 



insects was brought into the yellow light of a kerosene lamp, ics own light, 



by contrast, appeared of the characteristic phosphorescent greenish colour. 



One evening specimens of both species were secured and, in complete 



darkness, were with some difticulty induced to emit their light simultane- 

 ously. It was then seen that the light of the two species is very much 

 alike and of a greenish colour, that of Photuris Peiinsyivanica being of a 

 slightly stronger green. 



July, iqo.s. 



