182 THE CANADIAN ENTOMOLOGIST, 



Several authors have remarked upon the tendency of the winged 

 Lampyridae, in countries where large numbers of the same species are in 

 view at one time, to exhibit their light at rhythmic intervals. I have 

 never observed this in the United States, nor in those parts of tropical 

 America which I have visited. I think that, in this respect, there must 

 be great differences in the habits of the species. In travelling by night 

 on railroads in the Middle States, I have frequently seen in low and moist 

 lands near the road many thousands of these insects (chiefly Photuris 

 pensylvanica), which sparkled and twinkled to such an extent that one 

 might imagine himself on the Glittering Heath* itself, on which the hero 

 of the great epic of our race achieved his first victory, and gained his 

 double prize. But I have never seen any approach to a rhythmic effect 

 in these sparklings, as described in the books. 



The causes to which this singular phenomenon are ascribed are either 

 physical or physiological, t In order that my readers may give these 



* But lo ! at the last a glimmer, and a light from the West there came, 

 And another and another, like points of far off flame ; 

 And they grew and brightened and gathered, and whiles together they ran 

 Like the moon-wake over the waters, and whiles they were scant and wan. 



— Sigurd the Volsung, Book n, p. 137. 



t Proc. Ent. Soc. London, 1880, p. ii., Mr. McLachlan . . " had at that time 

 advanced the opinion that the phenomenon in question might be caused by currents of 

 air inducing the insects to simultaneously change their direction of flight." Sir Sidney 

 Saunders: "The simultaneous character of these corruscations among vast swarms 

 would seem to depend upon an intuitive impulse to emit their light at certain intervals 

 as a protective influence, which intervals became assimilated to each other by imitative 

 emulation." 



Ibid, p. vii. : "Mr. McLachlan, in connection with his idea of the supposed con- 

 temporaneous flashing of all the individuals in a swarm of Lampyrida?, called attention 

 to flies of the genus Arqyra, which when flying exhibited at times an appearance similar 

 to that of small snow-flakes, owing to the silvery pubescence with which part of the 

 body was clothed, but which was observed in certain positions, and especially when the 

 insects rested, owing to the pubescence being then concealed ; he thought this to some 

 extent was an analagous case to that of the light of swarms of Lampyridae." Sir Sidney 

 Saunders observed : . . . " as to the contemporaneous flashes of myriads, such as 

 are more frequently congregated on "the calmest nights, surrounding objects previously 

 involved in obscurity, become suddenly illuminated as if by electricity, and as rapidly 

 plunged into their antecedent gloom at alternate intervals. He could not concur in the 

 hypothesis that currents of air had any connection with such displays or exhibitions, 

 when not a breath was stirring around : nor that these manifestations might be evoked 



