The Ecologic Relations of the Photogenic Function among Insects. 305 



known to be attracted toward lights. Both sexes of Photuris pennsyl- 

 vanica, a species whose mating has been observed only rarelj, and in 

 wliich 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 tjpes of expression of 

 the photogenic function 

 among the Lampyrklae; 

 these are (A), 



are (^aj, that in 

 wliich the female emits 

 liyht 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 ligbt 

 until mated, typified by 

 Lampyris. In A, the males 

 are usually the more 

 brightly luminous; in B, 

 the females are usually the 

 brighter and frequently 

 apterous, while the males 

 may be nearly or entirely 

 non-luminous. Thesecond 

 type reaches its extreme 

 developmeut in Phengodes^ 

 e. g., P. luticollis [see Bar- 

 ber(l)]. Gorham(5)and 

 Olivier (14) have both 

 called attention to the re- 

 lations betweeu the deve- 

 lopment of the photogenic 

 apparatus and that of the 

 eves, 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 (Liicidota) atra, and it is said, EUychnia 

 corrusca. Phosphaenus hemipterus — apterouV, diurnal, and faintly lumi- 

 nous in both sexes and in the larva — seems to be quite anomalous, 

 and probably represents a degeneration. 



Photinus 

 pyralis. 



Photinus 

 consanguineus. 



Photinus 

 castus. 



Photinus 

 sointillans. 



Photinus 

 niargiuellus. 



Z,econtea 

 lucifera. 



Bogen XX der ^Zeitschr. f. vriss. Ine -Biologie", Druck vom 10. September 1914. 



