262 STUDY OF NATURAL HISTORY. 



traced downwards, into all the different orders 

 which compose a class. In proof of this we cite 

 the Hemiptera as the rapacious order of the Ptilota, 

 the Libellulince as the analogous group in the 

 Neuroptera, and the Prcedatores ( Chilopodomorpha 

 M'Leay) as the corresponding representation of 

 the Ferce in the order of Coleoptera. We merely 

 intimate these novelties in natural arrangement 

 (which will be separately treated of hereafter), to 

 show the importance of essential characters founded 

 upon the food of animals, or rather on the structure 

 by which its nature is indicated. 



(180.) Animals which are omnivorous, or de- 

 vourers both of animal and vegetable matter, pre- 

 sent a singular union of those characters which 

 respectively belong to the groups just mentioned. 

 Unless, therefore, we have a previous knowledge of 

 the circumstance, it becomes extremely difficult to 

 determine, from the simple examination of a dried 

 specimen, what was its natural food. The crow 

 family (Corvidce), which are the most perfectly 

 organised of all birds, are of this description. 

 They feed upon almost any thing which has life, 

 either animal or vegetable, and even upon Qarrion. 

 The toucans and the trogons belong to two different 

 tribes ; but as they are the points of union connecting 

 the Scansores and the JFissirostres, we find that both 

 partake of the same vegetable and animal diet. The 

 family of rats are likewise omnivorous, and by this 

 peculiarity they make the transition easy from the 

 carnivorous to the herbivorous quadrupeds. Such of 

 the tyrant fly-catchers of America as show a decided 

 affinity to the true shrikes, feed, like them, not only 



