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TEXT-BOOK OF ENTOMOLOGY 



undergo self-division, or to exhibit any appearance of giving rise to the blood- 

 cells (Wheeler). They have not yet been detected in Thysanura (Synaptera) 

 or in Myriopoda. 



d. The phosphorescent organs 



Phosphorescence is not infrequent in the Protozoa, coelenterates, 

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

 Crustacea, in myriopods (Geophilus), 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 fireflies, an Indian Buprestid (Bnprestis ocel- 



Fio. 388. 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; d, dorsal layer of the phosphorescent plate 

 penetrated by irregular tracheal branches, and rendered opaque by numerous urate concretions im- 

 bedded in it ;" v, ventral phosphorescent layer of the plate, with perpendicular tracheal stems whoso 

 branches, where they pass into capillaries, bear lumps which stain brown with osmic acid ; , 

 structureless substance (coagulum ?) filling the end of the last ventral segment. B, isolated por- 

 tion of the ventral layer of the phosphorescent plate : tr, tracheal stem surrounded by a cylindrical 

 lobe; p, parenchym cell attached to the cylinder; c, capillary, without the spiral threads; //), 

 coagulum stained brown. C, a tracheal stem of the ventral layer : at the fork of the brown-stained 

 capillaries are lumps stained brown with osmic acid. D, a part of C, more highly magnified, show- 

 ing the remains of the tracheal end-cells (to) enveloping the brown lumps (HI). After Emery. 



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

 luminous insects are the Poduran Anurophorus, Fulgora, certain 

 Diptera (Culex, Chironomus 1 and Tyreophora), and an ant (Orya). 



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

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

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

 photogenic organ is regarded by Wielowiejski and also by Emery as 

 morphologically 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. 



In Luciola as well as in other fireflies, including Pyrophorus, the 

 1 These midges owe their phosphorescence to bacteria in their bodies during disease. 



