210 THE SCOLYTID BEETLES. 



In other words, the physiological characteristics gave the best clue to 

 the natui'al affinities of the various groups and led to the discovery of 

 heretofore overlooked morphological characters which furnished 

 conclusive evidence of theii' true position. 



The close relationship between some of the existing representatives 

 of ancient groups of plants and representatives of evidently ancient 

 types of the beetles indicates that the beetles and plants may have 

 been closel}^ associated in their evolution from their respective primi- 

 tive forms. 



GEOGRAPHICAL DISTRIBUTION IN ITS BEARING ON TAXONOMY. 



Superfamily SCOLYTOIDEA. 



It is evident from our present knowledge that the superfamily 

 Scolytoidea is represented to a greater or less extent in every section 

 of the world where woody plants grow. 



Family IPIDiE. 



The famity Ipidae is also represented by species in all of the great 

 faunal regions. The subfamily Cryphalinse, with its widely dis- 

 tributed Hypothenemus, Stephanoderes , and Xylehorus, has a wider 

 range of distribution perhaps than is found in any of the other sub- 

 families. The IpinaB are more restricted to the Holarctic regions and 

 to the distribution of Pinus and its allies, Ahies, Picea, Larix, etc. 

 The Corthylinge are more restricted to temperate, subtropical, and 

 tropical America except in the genus Xyloterus, which extends 

 through the Palsearctic and Nearctic regions. The Micracinse, with 

 the exception of Liparthrum and Hypohorus, are largely restricted to 

 north temperate America. In Crypturginse the genus Aphanar- 

 thrum is restricted to Madeira and the Canary and Cape Verde Islands, 

 while Crypturgus has a wide range through the Palsearctic and Nearc- 

 tic regions, and Dendroctonus, with one exception, is confined to North 

 and Central America. The Phloeotribinse and Hylesininse are widely 

 distributed throughout the regions of tree growth. 



Family SCOLYTID^. 



The family Scolytidae, as represented by the genus Scolytus, extends 

 over a wide range of the Palsearctic and Nearctic regions, but the 

 greater number of genera and species are evidently to be found in the 

 subtropical and tropical regions of Central and South America. 



Family SCOLYTOPLATYPODID^. 



The family Scolytoplatypodidse, so far as known, is restricted to 

 small sections of the eastern Palseaictic and of the Ethiopian regions. 



