308 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1911. 
originated, and why? The phylogenetic problems are certainly very 
interesting, and present remarkable instances of ‘‘convergence.” It 
is hoped to collect some of these cases and develop them in a future 
paper. 
5. FLUORESCENT SUBSTANCES IN LUMINOUS INSECTS. 
An interesting circumstance in this connection is the existence in 
certain luminous organisms of a substance whose solutions exhibit a 
brilliant blue fluorescence. Dubois (? ™) found this substance in 
the cucuyo, and in Luciola atalica, and named it ‘‘Pyrophorine,”’ from 
Pyrophorus noctilucus, the entomologic name of the cucuyo. More 
recently Coblentz () has found it in Photinus pyralis, Photinus cor- 
rusus, and Photuris pennsylvanica, anc the author has found it in 
Photinus consanguineus, P. scintillans, and Lecontea lucifera. It is 
also present in the larva of Photinus pyralis, and in other lampyrid 
larve. Dubois ( 1 1) regarded this substance as a glucoside, 
analogous to esculin (a glucoside which is present in the bark of the 
horse-chestnut, and whose solutions possess a blue fluorescence), 
while the present author (*7) concluded that it had an alkaloidal 
nature, and not at the time being aware that Dubois had offered the 
name ‘“‘Pyrophorine” for the fluorescent material from the cucuyo, 
suggested the name ‘‘Luciferesceine” for the substance from the 
Lampyridae. Neither view as to its chemical nature is at all definite, 
however, and more work will be necessary to elucidate this point. 
Fluorescent extracts of the pyralis are produced by extraction with 
alcohol, ether and water, but not by chloroform, benzene, or carbon 
tetrachloride. The fluorescent material is not precipitated by lead 
acetate, mercuric chloride, ammonium sulphate, nor chlorplatinic 
acid. It appears to be a solid at ordinary temperatures, though as 
emitted by the insect it is contained in a sticky exudation, which 
soon hardens in the air. 
Luciferesceine dissolves readily in liquid ammonia, the solution 
presenting the blue fluorescence characteristic of aqueous and alco- 
holic solutions, the solution itself being very pale yellow. 
Dubois seems to have regarded this substance as of use to the 
insect in transforming useless into visible radiation, and thus improv- 
ing the quality or intensity of the emitted light; and he states that on 
this theory he first advanced the idea of the use of fluorescent mate- 
rials with artificial iluminants to improve the quality of the light, 
as is now. done in the use of rhodamine with the mercury vapor arc. 
Two things, however, stand in the way of the acceptance of the view 
that the fluorescent property of this substance is of use to the insect; 
first, the internal juices of the insects (at least of Photinus pyralis) 
are slightly but distinctly acid, and it has been found that even a 
weak acid reaction destroys the fluorescence; second, Ives and Co- 
