Nature's Night Lights. 173 
place are simultaneously affected in the same way, 
and at such times they mass themselves together in 
myriads, as if for migration, or for some other great 
purpose. Mr. Bigg- Wither, in South Brazil, and 
D’Albertis, in New Guinea, noticed these firefly 
gatherings ; I also once had the rare good fortune 
to witness a phenomenon of the kind on a very grand 
scale. Riding on the pampas one dark evening an 
hour after sunset, and passing from high ground 
overgrown with giant thistles to a low plain covered 
with long grass, bordering a stream of water, I 
found h all ablaze with myriads of fireflies. I 
noticed that all the insects gave out an exceptionally 
large, brilliant light, which shone almost steadily. 
The long grass was thickly studded with them, 
while they literally swarmed in the air, all moving 
up the valley with a singularly slow and languid 
flight. When I galloped down into this river of 
phosphorescent fire, my horse plunged and snorted 
with alarm. I succeeded at length in quieting him, 
and then rode slowly through, compelled to keep 
my mouth and eyes closed, so thickly did the insects 
rain on to my face. The air was laden with the 
sickening phosphorous smell they emit, but when I 
had once got free of the broad fiery zone, stretching 
away on either hand for miles along the moist valley, 
I stood still and gazed back for some time on a scene 
the most wonderful and enchanting I have ever 
witnessed. 
The fascinating and confusing effect wdiich the 
appearance of fire at night has on animals is a most 
