June, 1896.] Packard: Phosphorescent Organs of Insects. 



61 



THE PHOSPHORESCENT ORGANS OF INSECTS. 



By a. S. Packard. 



The nature of the phosphorescent organs and their physiology has 

 never seriously engaged the attention of students in this country, and I 

 have thought that some account compiled from the latest and best re- 

 searches might stimulate inquiry in this country, where fire-flies are 

 universally common. 



Phosphorescence is not infrequent in the Protozoa, Ccelenterates, 

 Worms, and has been observed in the bivalve Pholas, in a few abyssal 

 Crustacea, in Myriopods {Geophtiits), in an Ascidian, Pyrosoma, and 

 in certain deep-sea fishes. 



In insects luminosity is mostly confined to a few Coleoptera, and 

 besides the well-known fire-flies, an Indian Buprestid {Buprestis ocel- 

 lata) is said to be phosphorescent; also a Telephorid larva. Other 

 luminous insects are the Poduran Anurophorus, Fulgora, and certain 

 Diptera (^Ciilex and Tyreophora). 



The seat of the light is the intensely luminous areas situated either 

 in the head (Fulgora), in the abdomen (Lampyridae), or in the thorax 

 (in a few Elateridae of the genus Pyrophorus). The luminous or photo- 

 genic organ is regarded by Wielowiejsky and also by Emery as morpho- 

 logically a specialized portion of the fat-body, being a plate consisting 

 of polygonal cells, situated directly under the integument, and supplied 

 with nerves and fine tracheal branches. 



P -,.■ 



Fig. A. Sagittal section through the hinder end of a male Luciola ; the 

 organs above the phosphorescent plate only drawn in outline, s, integument of the 

 last segment, somewhat removed by the section-knife from the phosphorescent tissues. 



