NATURAL AFFINITIES OF SCARAB^I. 27 



I shall for the present confine my remarks to the Peta- 

 locera. These appear to branch out into two columns of 

 five families each ; one of the columns consisting of Sapro- 

 phagous insects, or such as feed on putrid or decomposed 

 vegetable matter, and the other of Thaler ophagous insects, 

 or such as live on green or fresh vegetable food. The 

 saprophagous column answers to the " Scarabeesde terre" 

 of De Geer, and the Scarabees des jieurs et ceux des ar~ 

 bres of the same author are both comprised under the 

 name of Petalocera thaler ophaga. Itisalso observable that 

 each column consists of two groups ; the first, of insects 

 which have membranaceous maxillae, and therefore live on 

 juices, and as it were by licking their food ; and the second, 

 of insects which have corneous or crustaceous maxilla?, 

 and therefore live on a more solid species of food, and by 

 mastication. 



It will next be remarked, that the families in one of 

 these columns have each a striking similarity of general 

 form to the corresponding families in the other column : 

 thus the Rutelidcc and Geotrupidce have their body in ge- 

 neral subconvex; the Scarabaida and CetoniidcE have it 

 generally depressed; the jlphodiidcc and Glaphyrida less 

 so; the Trogida and Melolonthidce have it very convex, 

 while the Dynastidce and Anoplognat hides have this sort 



which shall not lead to an artificial distribution. For were the young 

 entomologist to insist upon every one of the four characters in the definition 

 being distinct, he would necessarily exclude from the group many Histeres 

 because not herbivorous, the genus Trachyscelis because not pentamerous, 

 the genus Platyctrus because the antennae are scarcely clavate, and many 

 of the genus Trox because the anterior tibiae are not always externally 

 spinose. It may however be safely asserted, that when any insect does not 

 possess some two of these four characters, it ought not to be considered as 

 belonging to the group. 



