1910 Canadian Entomologist  
connection with the collection of specimens for some work on physiologic light, I have had occasion to observe the modes of lightemission of some species of American Lampyridz cornmon i11 this neighbourllood (Washington, D. C.), and thought that some of these might be of interest. Tlie species most common here, at least within the city limits, is Photinuspymlis Linn.; Photi?zus consn~zguineus Lec., Phoz'i?~tts scir~tiG Zanr Say, Photuris pen~zsyLvnnicn Geer, and Lecontea (Pyf-nclomena) nngw'atn
more » ... Say, were also observed. Eac11 of these species appears to emit its light in a different and characteristic way-sometimes in several ways. The insect whose light-emission is best known here is the Photinus pymlis. This is the insect which abounds in our parks during the summer, and with whose peculiar ifdipping" fl~ght as it flashes most of us Washingtonians are familiar. 'This dipping flight is indulged in by the male, apparently while seeking its mate, and consists usually of a short downward fl~ght, followed by a longer upward fl~ght, during the whole of which the insect emits a continuous light, the whole phenomenon occupying fro111 half a second to a second. The light appears to be at its maximum brilliancy during the turn at the lowest point of the flight, increasing rapidly on the descending flight, and decreasing on the ascending. At the completion of the flash the insect remains dark for some seconds, or perhaps minutes, and then repeats the operation, either near the same locality, or after a fl~ght to some point usually not far from its starting point. Sometimes the light does not entirely die out imnlediately after the flash, but a phosl~horescent glo~7 is left shining for some seconds, sometimes till the next flash-and by this residual glow the insect may be trailed with ease at night. Later in the evening the insects fly higher, and then flash when flying straight, or, indeed, in any direction ; the dipping flight appears to be indulged in only when near the earth. Occasionally they flash near the earth when flying in a curve the reverse of that described, that is, a rising flight followed by a descending one ; rarely, also, they may be observed to twinkle, as will be described for the PAoturis. This de~cription applies only to the male pyralis. The luminous organ of the male of this species occupies the entire ventral surface of the two abdominal segments next to the last, as well as a good poltion, almost half, of the preceding segment. T h e luminous organ of the female occupies only a small spot, about a third of the ventral area, of the third N o~e m h e r , 1910
doi:10.4039/ent42357-11 fatcat:efrkmfyymvehfgxmzyt6cafuru