ON DECOMPOSED VEGETABLE MATTER. 55 



which are membranaceous and concealed under the cly- 

 peus in the other. But let this sole distinction be over- 

 looked, and some of the Geotrupidcc, such as the genus 

 Athyreus, will find a place among the Scarabceida. 



The Scarabaidce are all strictly coprophagous ; and this 

 great affinity in their manner of living is in all probability 

 the cause of the organs of manducation being so similar 

 throughout the family, as by no means to supply the di- 

 stinctive characters that might have been expected from 

 the marked variety of their general forms. Owing to this 

 extraordinary similarity in the instrumenta cibaria of the 

 different insects Avhich compose the group, Latreille has 

 more than once proposed to make but one genus of them, 

 ascribing to the modern genera the name of sections. But 

 though I have had reason to know that the father of mo-* 

 dern entomology is far from thinking that genera, as com- 

 monly understood, exist in nature, it is nevertheless easy 

 to perceive that alterations of the above sort must resolve 

 themselves into the idea of natural genera. For if the 

 animal creation knows any other absolute distinction than 

 that of sex and species, and the groups insulated by these 

 other absolute distinctions are to be termed genera, it is 

 clear even to an axiom, that where such natural divisions 

 cease to be apparent, genera can be said no longer to exist. 

 Nothing, however, has yet occurred in the course of my 

 observation but what has demonstrated the truth of the 

 principles upon which the present investigation was com- 

 menced. These were, as I have already stated, that any 

 other difference that may exist between animals than those 

 of sex and species, is not absolute, but must be considered 

 as arising solely from the imperfection of our own know- 

 ledge of Nature's productions; and that genera consequently 



y 



