The Ecologic Relations of the Photogenic Function among Insects. 305 
known to be attracted toward lishts. Both sexes of Photuris pennsyl- 
vanica, a species whose mating has been observed only rarely, and in 
which the relation of the luminosity to mating is unknown, come to 
light quite frequently. 
Mast (10) has shown that the orientation of the male Photinus to 
the female after her response, is extremely accurate, and takes place 
after the stimulus has ceased, in entire darkness, thus offering an ob- 
jection to Loeb’s theory of phototropism. — 
There appear to be two main or general types of expression of 
the photogenic function 
among the Lampyridae; 
these are (A), that in 
which the female emits 
light in flashes, and only 
in answer to a male (or 
to artificial stimulus), ty- 
pified by Photinus; and (B), 
that in which the female 
exposes a continuous light 
until mated, typified by 
Lampyris. In A, the males 
are usually the more 
brightiy luminous; in B, 
the females are usually the 
brighter and frequently 
apterous, while the males 
may be nearly or entirely 
non-luminous. The second 
type reaches its extreme 
development in Phengodes, 
e.g., P. laticollis [see Bar- 
ber (1)]. Gorham(5)and 
Olivier (14) have both 
called attention to the re- 
lations between the deve- 
lopment of the photogenic 
apparatus and that of the 
eyes, antennae, etc., in the 
sexes. As a general rule 
the eyes of the males are 
larger and their antenae 
longer than those of the 
females, the extreme being 
represented by Phengodes. 
Some species which in the adult stage are diurnal and have either no 
luminous apparatus, or organs which are non-functionating, in the larval 
stage possess organs as highly developed as have the larvae of the brightly 
luminous species; such are Rileya (Lucidota) atra, and it is said, Ellychnia 
corrusca. Phosphaenus hemipterus — apterous, diurnai, and faintly lumi- 
nous in both sexes and in the larva — seems to be quite anomalous, 
and probably represents a degeneration. 


eo] () 
BER ANREBEE Photinus 
ZUaumamanımı 
Ze 
Ka] 

Photinus 
consanguineus. 
Photinus 
castuıs. 
Photinus 
sointillans. 
Photinus 
imarginellus. 
I,econtea 
lucifera. 
Bogen XX der „Zeitschr. f, wiss. Ins -Biologie“, Druck vom 10. September 1914. 
