](J8 INTRODUCTORY. 



occupying situations which were so far from being insu- 

 lated, that they showed the existence of such insects to be 

 necessary in order to complete the chain of connexion. It 

 was thus I learned, that the transition from one of the 

 families I had instituted to the other was so regular, both 

 in their habits (as far at least as had been observed) and 

 their general appearance, that no greater separation could 

 be drawn between them than such as might arise from the 

 idea of there being five principal points, knots or types of 

 form in every circle, to one or other of which all the ani- 

 mals in that circle might be referred. With this idea of 

 the Petalocerous insects, I was naturally induced to exa- 

 mine the Lucani of Linnaeus to which the passage was so 

 evident by means of the genus Lethrus. The result of 

 this examination, while it served to convince me that the 

 general disposition of the Lucani was similar to that which 

 had been so satisfactorily demonstrated to exist among 

 the Petalocera, still, to my vexation, left several chasms 

 that made the new circle far less perfect than those into . 

 which the Scarabai had just been resolved. The atten- 

 tion however of certain friends, who with the greatest li- 

 berality laid their entomological collections open to my 

 scrutiny, soon removed almost all those difficulties, and I 

 became anxious to know whether the same regularity held 

 good generally among the other Coleoptera. The Luca- 

 iiida of Latreille being a family the insects of which are 

 known to live in their perfect state on green or living vege- 

 table matter, they seemed to form a parallel to the Thale- 

 ropkagous Petalocera ; and the question that presented it- 

 self was, whether any animals exist agreeing more nearly 

 with the Lucani in general character than with any other 

 tribe of insects, but which nevertheless differ from them 



