MUTUALISTS. 69 



We find many on the surface of the scales, and others 

 ■which conceal themselves at the bottom of mucous 

 canals. We have brought together only a few examples, 

 and there are certain others which are mentioned else- 

 where, but which ought more properly to be placed 

 here. 



The insects long known under the name of Ricini, 

 and to which many other appellations have been given, 

 deserve to figure in the .first rank in this group. They 

 have always perplexed entomologists,, who seem to 

 consider them as parasites allied to acaridae and lice. 

 It has, however, been long known that they have no 

 trunk to suck with, and that they have two small scaly 

 teeth, which rather serve for the purpose of biting. A 

 long time since, the examination of their stomach 

 proved that they contain only morsels of skin instead 

 of blood. This has induced many entomologists to 

 place them in the same order as grasshoppers, that of 

 Orthoptera. 



Lyonet has given figures of several of those which 

 he studied with the care -which he so well knew how to 

 employ in his anatomical investigations; and in 1818 

 Nitzsch, a professor at Gottingen, had brought together 

 so great a number of them, that it required several days 

 to examine his collection ; he began the publication of 

 his catalogue, but has not had time to finish it. Several 

 other entomologists and anatomists have since taken up 

 the subject. 



We owe the description of several hundred species to 

 Mr. Denny. Mons. F. Eudow has lately made known 

 a great number of species which he has collected from 



