150 INTERNAL ANATOMY OF INSECTS. 



gingly communicated to me. He remarks that in a box 

 in which glow-worms were kept five luminous specks 

 were found secreted by the animal, which seemed to glow 

 and were of a different tinge of light. One put into olive 

 oil at eleven p. M. continued to yield a steady and unin- 

 terrupted light until five o'clock the following morning, 

 and then seemed, like the stars, to be only absorbed by 

 superior effulgence. The luminous spherical matter of 

 the glow-worm is evidently enveloped in a sac or capsule 

 perfectly diaphanous, which when ruptured discloses it 

 in a liquid form, of the consistency of cream. M. Ma- 

 caire, he observes, in the Bibliotheque Universelle, draws 

 the following conclusions from experiments made on the 

 luminous matter of this animal ; that a certain degree 

 of heat is necessary to their voluntary phosphorescence 

 that it is excited by a degree of heat superior to the 

 first, and inevitably destroyed by a higher that bodies 

 which coagulate albumen take away the power that 

 phosphorescence cannot take place but in a gas contain- 

 ing no oxygen that it is not excited by common elec- 

 tricity, but is so by the Voltaic pile and lastly, that 

 the matter is chiefly composed of albumen. 



xii. Fat. There is one product found in the body of in- 

 sects most copiously in their larva state, but more or less 

 also in the imago, which may be called their fat. In the 

 former it is a many-lobed mass, occupying the whole of 

 the interior, except the space that is required for the 

 muscles and the internal organs, which it wraps round 

 and protects. It is contained in floating membranes, 

 very numerous, which fill all the interstices, and assume 

 the appearance sometimes of small globules, and some- 

 times of a thickish mucilage, which easily melts and in- 



