DISTINCTIONS OF CETONIAD^K AND SCARAB.ETD^. 209 



in the construction of their tarsi. The Cetoniadce are 

 arboreal beetles ; that is, living and moving among those 

 trees, plants, and flowers, which are their natural food. 

 Their feet are accordingly constructed for clinging to 

 objects which afford them such an uncertain footing. 

 The terminal joint of the tarsi, on which are the claws, 

 is that in which the greatest strength is necessary ; and 

 it is therefore invariably longer and stronger than any 

 of the others. Hence these insects cling with the greatest 

 pertinacity, frequently by only two or three of their feet, 

 to any object they catch hold of. The more equal ar- 

 ticulation, also, of all their legs, gives to these members 

 a freedom of motion which is denied to all other of their 

 affinities. In the genera Cetonia and Rutila (which, 

 as being types of the family, possess this structure in 

 the greatest perfection), the claw joint is sometimes as 

 long as the total length of all the others ; and even in 

 the more aberrant groups, the united length of all the 

 tarsi is fully equal to that of the shank. Now, all these 

 characters, in the Scarabaidce, are completely reversed. 

 Hence it is, that the two families admit of the most 

 simple, as well as natural, definition. The entomologist, 

 in short, has only to remember, that in the arboreal, or 

 Thalerophagous Cetoniadce, the tarsi are as long, and 

 generally longer, than the shank ; while in the terres- 

 trial, or Saprophagous Scarabceidce, the tarsi are invari- 

 ably much shorter than the shank : in other words, that 

 they are long in one, and short in the other. Having 

 now sufficiently defined the present family by its typical 

 peculiarities, we may proceed to its next subordinate 

 divisions, or sub-families. These, with but one excep- 

 tion, we shall distribute according to the arrangement 

 developed by Mr. MacLeay ; not that the groups them- 

 selves have yet been studied with that precision which 

 they require, but because, so far as we have verified 

 this theory, we find it, with but one exception, to har- 

 monise with the general plan upon which all the great 

 divisions of the animal kingdom are founded. 



(182.) The five principal groups, or sub-families, 



