HISTORY OF ENTOMOLOGY. 
481 
than I can afford ; I must therefore refer you to his 
work for more particular and detailed information on 
that subject. With regard to the analogy between op- 
posite points of contiguous circles, you may get a very 
good idea of it from his diagram of Saprophagous and 
Thalerophagous Petalocerous beetles, which I here 
subjoin. 
It is a very singular circumstance that in these two 
circles we have two sets of insects,— one impure in its 
habits and feeding upon putrescent food, and the other 
clean and nourished by food that has suffered no decay,— 
set in contrast with each other, and that in each of the op- 
posite groups, the one has its counterpart in some respect 
in the other. In none is this more striking than the Sca- 
rabceidce and Cetoniadce, both remarkable for havino- soft 
membranous mandibles unfit for mastication, and both 
living upon juices, the one in a putrescent and the other 
in an undecayed state a . 
a Other systems or methods have been promulgated by various 
authors, as by Schaiffer, Scopoli, Geoffroy, &c. Walckenaer and 
Blainville have proposed one founded on the number of the legs of 
insects ; but those in the text are the principal and best known. 
—N. Did. tTHist. Nat. xvi. 277. 
VOL. IV 
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