OF INSECTS. ] 73 



attenuated and capable of being raised like a thin 

 plate. " Its exterior face presents a net- work of 

 hexagonal meshes, resembling that of the epidermis 

 of plants. Each hexagon is convex, and has a conical 

 hair in its centre, directed backwards. The rest of 

 the surface is simply covered with small asperities, 

 and the opposite or inferior face is concave and smooth. 

 Each of the luminous points is thus composed of a 

 multitude of facets, and forms an apparatus entirely 

 similar to that which Fresnel has invented for the 

 diffusion of light, and which bears his name. When 

 this corneous cap is removed, the luminous matter 

 loses a great part of its brilliancy. Every thing, in 

 other respects, is managed with a view to increase 

 the light to the utmost. The largest and most regu- 

 lar facets occupy the centre, arid the smaller ones 

 are placed at the sides, regularly decreasing in size. 

 The hairs tend to prevent the dust settling, and the 

 larva is possessed of a kind of anal brush, which it 

 can employ in cleaning them."* 



The phenomenon in question is almost confined to 

 the Coleoptera, and among these to the families 

 Ekteridae and Lampyridae. About thirty luminous 

 species of the former are known, and nearly 200 of 

 the latter, four of which are indigenous to Europe.t 



NERVOUS SYSTEM. The important and singular 

 department of the animal economy now to be briefly 

 considered, is rather of a simple nature in insects, 



* Lacord. Intro, a P Ent. II. 147. 



f Examples of both will be found figured and described 

 in our Coleopterous Vol. p, 161-172. 



