PHOSPHORIC INSECTS. 145 



nous substance has been extracted froiii the in* 

 sect's body. According to Cams,* the light, when 

 extinguished in the dry luminous matter, reap- 

 pears when the latter is damped with water. The 

 naturalist Boitard has made a similar assertion ; 

 speaking of the glowworm' s light, he says : " II 

 parait qu'ils peuvent a volonte augm enter oil 

 diminuer cette singuliere lumiere, qui disparait 

 lorsqu/ils sont morts, mais settlement par le des^ 



We are thus led to infer that the luminous sub- 

 stance of glowworms is permanently phosphores- 

 cent even after death, if the tissue of the lumi- 

 nous organ be kept dry, and not decomposed by 

 chemical means. 



When the insect, dead or living, is plunged 

 into boiling water, its light is extinguished sud- 

 denly. A vigorous individual plunged into olive 

 oil soon loses its brightness, but a feeble lumi- 

 nosity persists for a long time even after death. 



The microscope shows us in the luminous sub- 

 stance of glowworms a cellular tissue, filled with 

 what appears to be a soft yellowish grease ; the 

 whole is traversed by the trunks and branches of 

 the tracheae or air- tubes. This substance extends 

 in a thin layer along the inner sides of the ab- 

 domen. It is this greasy substance, this corps 

 graisseux, that Treviranus regarded as the source 

 * Comp. Anat. f ' Manuel d'Entomologie.' Paris, 1828. 



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