208 



THE SCOLYTID BEETLES. 



shrub or tree. Indeed it is found that the species of an entire genus 

 of beetles may confine their breeding places to a restricted part of 

 the plants of a single genus or closely allied group. Therefore even 

 the part of the plant infested by a species may be of considerable 

 taxonomic importance in indicating the natural position of a species 

 or genus of heretofore doubtful position. 



Condition of the Plant. 



The condition of the plant or plant tissue at the time it is occupied 

 by the beetles is of considerable systematic and economic importance. 

 It ranges from young to old plants, living, declining, dying, and dead, 

 and to different stages of decay of the plant or some part of its tissue. 

 The fact that there is a relation between the species of beetles and 

 one or more of the conditions mentioned shows that there is some- 

 thing of taxonomic value in this phase of the subject. 



Kelation of the Species of Beetles to the Systematic Posi- 

 tion OF Their Host. 



The primary and minor divisions and groups of plant species repre- 

 sented in which one or more species of beetles live range from the 

 fruiting bodies of certain fungi of the Eumycetes to the liigher flower- 

 ing shrubs and trees of the Angiospermse, the greater number of spe- 

 cies and genera being confined to the Pinacese of the Gymnospermse 

 and the shrubs and trees of the Dicotyledonege of the Angiospermse. 



Range of Host Plants. 



The range of host plants in the families of the Scolytoidea may be 

 designated as follows : 



Table VIII. — Range of host plants in the families of Scolytoidea. 



Family in the Scolytoidea. 



Group of host plants. 



Fungi. 



Gymno- 

 spermse. 



Monocoty- 

 ledoneae. 



Dicoty- 

 ledonese. 



Ipldse 



Scolytidag 



Scolytoplatypodidse. 

 Platypodidae 



Rare. 

 None. 

 ..do.. 

 ..do.. 



Common. 



Rare 



None 



Common. 



Rare. 

 None. 

 ..do.. 

 ..do... 



Common. 

 ...Do. 

 Rare. 

 Common. 



The range of host plants in the genera of true barkbeetles is usually 

 more restricted and characteristic than in the genera of ambrosia 

 beetles or in those species which live in dead or decaying bark or 

 wood. 



Examples of restricted range of host ijlants. — In the Cryphalinse we 

 find that Cryphalus is partial to Abies and Picea; Trypophloeus to 



