OF THE LUMINOUSNESS OF INSECTS. 491 



families are the Elaters and the Lamprodea. Among the Elaters we 

 know as luminous the E. noctilucus, E. ignitus, E. lampadion, E. 

 retrospiciens, E. lucidulus, E. lucernula, E. speculator, E. Janus, 

 E. pyrophanus., E, luminosus, E. lucens, E. exstinctus, E. ciicujus, 

 E. lucifer, and E. phosphorens * . In all of these there are two bright 

 oval, convex spots upon the thorax, which, after death, are of a greenish 

 yellow, and whence light, whilst living, streams forth, and in addition 

 to which there are two other spots upon the abdomen that are luminous, 

 and which, during repose, are concealed beneath the elytra. Indeed, 

 the whole inside of the body is luminous, but it is concealed by the 

 impenetrable integument, and only sometimes upon the very great 

 expansion of the abdomen is it perceptible through the divisions of the 

 segments. All the named species are found in tropical America, and, 

 according to Sloane, repose during day in dark shady places, and only 

 flv during dusk and at night, when they betray themselves by their 

 light ; but, according to Sieber, they also fly at noon in the sunshine, 

 but then exhibit no light. Their light is of a bright blue-white colour, 

 and in the larger species, for instance, in E. noctilucus^, it is so strong, 

 that, by its aid, small writing may be read at night if the luminous 

 spots be passed regularly over the lines. Some naturalists who have 

 had the opportunity of observing the insect in its native country (Spix) 

 assert that they have found beneath the luminous spots a yellowish 

 glandular mass, to which a multitude of branches of the tracheae are 

 distributed from the approximate main stems. These are the true 

 luminous bodies whence the light streams forth either brightly or dully, 

 according to the quantity of air the insect admits to them by respiration. 

 It is also said that the insect can prevent the emission of all light by, 

 according to Spix, preventing the admission of any air. Amongst the 

 natives, all these insects are called Cucujos or Cucujii ; they use them 

 as ornaments for their dresses by night, and they are worn by the 

 females especially as ornaments to the head-dress, and the Indians are 

 said to bind them to their feet on a journey, to enable them to discern 

 their road more distinctly- According to Piedro Martire J, the 

 inhabitants of Saint Domingo keep the luminous Elaters in their rooms 



* See Illiger in the Magazin der Geselsch. naturf. Freuride zu Berlin, vol. i. p. 14. 

 \ See Curtis in Zoological Journal, 1827, No. 2, p. 379. Heusinger Zeitschrift, vol. iii. 

 Pt. 1, p. 137. Thons Archiv. vol. ii. Pt. 2, p. 63. 

 In Kirby and Spence, vol. ii. p. 462. 



