599 
1884.] The Luminosity of Luciola Italica. 
not a ready-formed colouring-matter, but what is known 
among tinctorial chemists as a chromogen, — a substance 
capable of yielding a colour under some external influence, 
here doubtless the oxygen of the atmosphere. To test 
this supposition I placed leaves to which pupae were attached 
in gaseous mixtures free from oxygen, but the specimens 
died, as I had feared might happen. 
I am sorry at having to exhibit an insect so useful to man, 
and which shares with Cock-Robin the honour of figuring 
in the nursery-rhymes of most nations, in the odious cha- 
racter of a cannibal. Would that some of our enemies — 
such as the house-fly, the wireworm, the crane-fly, &c. — - 
would develop the same habit ! 
IX. THE LUMINOSITY OF LUCIOLA ITALICA. 
c^HIS inseCt, belonging to the family of the Lampyridae, 
is very abundant in the neighbourhood of Bologna. 
S. C. Emery has taken the opportunity of submitting 
them to a thorough examination, both as regards the ana- 
tomical structure of their luminous 'organs and as to the 
chemico-physiological process upon which the production 
and emission of light depend. His observations were much 
interfered with by the unfavourable character of the weather 
during the summer of 1883, so that only the anatomical part 
of his researches can be regarded as completed. 
According to his observations, as recorded in the “ Zeit- 
schrift fur Wissenschaftliche Zoologie,” the luminous organs 
consist of continuous plates, consisting of single lobes in 
which the terminal ramifications of the tracheae, the tra- 
cheal capillaries, open without communicating with each 
other. 
The male Luciolae give out light in two distinct modes : 
in the night, when they are brisk and fly about, the light 
increases and decreases in short regular intervals, so that it 
seems to twinkle. If one of them is caught flying, or dis- 
turbed in its rest by day, it shines less than at the maximum 
of its intensity when on the wing, but without intermission. 
It is remarked, however, that the luminous plates do not 
