EXPERIMENTS WITH ELECTRIC LIGHT. 201 
object, I prepared some nests 12 inches long by 6 inches 
wide; and Mr. Cottrell kindly arranged for me at 
the Royal Institution on the 29th of June, by means of 
the electric light, two spectra, which were thrown by two 
glass prisms on to a table at an angle of about 45°. 
Each occupied about 6 inches square, and there was a 
space of about 2 inches between them—that is, between 
the red end of the one and the violet of the other. 
Experiment 1.—In one of the spectra I placed a nest 
of Formica fusca, 12 inches by 6, containing about 
150 pupe, and arranged it so that one end was distinctly 
beyond the limit of the violet visible to us, and all but 
to the edge of the green given by thalline paper, and 
the other just beyond the visible red. The pup# at first 
were almost all in or beyond the violet, but were carried 
into the dark space between the two spectra, the bright 
thalline band being avoided, but some pupz being 
deposited in the red. 
Experiment 2.—I then tried the same experiment 
with a nest of Lasius niger, in which there were many 
larvee as well as pups. They were all at the commence- 
ment at the blue end of the nearer spectrum. The 
larvee were left by themselves in the violet, while pup 
were ranged from the end of the green to that of the 
red inclusive. 
Experiment 3.—Arranged a nest of L. niger as 
before ; at the commencement the pup and larve were 
much scattered, being, however, less numerous in the 
violet and ultra-violet rays. Those in the ultra-violet 
