Relationships existing amongst Natvral Objects. 417 



supposition that he observes, " Habitat in Georgise forsan aquaticis ?" He how- 

 ever noticed several circumstances which seemed to indicate an approximation 

 towards Lebia, Dromius, Tarus, &c. ; and Dejean, without being aware at the 

 time of the observations of Mr. Kirby, placed it in the subfamily Truncati- 

 pennes {Brachinidw, MacL.), with some of the genera of which group, such 

 as Coptodera, Orthogonius, Thyreopterus, &c. these insects seem to me to be 

 most nearly allied. 



It is certainly a curious fact in the geographical distribution of Insects, that 

 so aberrant a form as is indicated by the four insects noticed above should be 

 found in regions so distant as North America, Brazil, and New South Wales. 

 This fact alone I should imagine must be considered sufficient to prove that a 

 wide geographical range is not the character of a typical group, as stated by 

 Mr. Swainson. 



The two insects represented in the accompanying figures 5 and 6, are Rhy- 

 zopertha, (Steph.) pusilla (Fabr.), and Tomicus (hdiiv.)fuscus (Marsh.), which 

 in their xylophagous habits, cylindrical form, pitchy-ferruginous colour, punc- 

 tated surface, transversely rugose thorax extending over the concealed head, 

 dentate tibiae, and short antennae, are so very nearly alike, that by many au- 

 thors they have been even placed in the same genus. A minute investigation 

 of their structure proves them however to be totally different in their essential 

 organs, the antennae, tropin and tarsi. In these respects Tomicus will be found 

 to belong to the group having the elm-destroying Scolytus as its type ; whilst 

 Rhyzopertha is most nearly allied to the genus Bostrichus of Geoffroy (Der- 

 mestes capucinus, Linn.). These two groups have indeed by many persons 

 been considered to belong to the same family Bostrichidoe ; and even by those 

 who have ventured to place them in different groups, they have been made to 

 follow each other without any intervening link ; being indeed employed when 

 thus connected to form the transition between the Pentamerous Ptinidce and 

 the Pseudotetraraerous Curculionidce, to which last Scolyttis most intimately 

 approaches. 



That the relation between these two groups, notwithstanding the many 

 points of connexion, in habit, economy, and even structure, is not an affinity, 

 but merely an analogy, I entertain very little doubt, but our comparative 

 ignorance of the structure and larvae of the Xylophagous insects of Latreille 



3 I 2 



