202 THE SCOLYTID BEETLES. 



lei evolution due to a common tendency which may lead to the same 

 or similar results during the same or similar stage in the evolution 

 of the species. 



While the varyijig types of the egg and brood galleries furnish 

 some very important taxonomic evidence, any attempt to classify 

 the species of a family or subfamily according to such characters 

 alone would give the same heterogeneous results as are found in the 

 different classifications based on the elements of a single external or 

 internal part or organ of the body. On the other hand, if the galleries 

 of the species of the major and minor divisions of a subfamily are 

 studied separately, it will be found that the character of the gallery 

 and the species of the host tree will serve as most important guides 

 to the natural position of a species or group of allied species. 



TERMINOLOGY OF THE GALLERIES. 



Following is a revised list with definitions of the terms used to 

 designate the different elements of the scolytoid gallery. 



Egg gallery. — The egg gallery is the burrow excavated by the parent 

 beetles preliminary to depositing the eggs in niches along the sides 

 or loosely in the gallery itself. 



Social gallery. — The social gallery is one in which all stages of the 

 broods from the eggs to the matured individuals and the parents 

 live, as in Xylehorus, certain species of Platypus, Crossotarsus, etc. 



Social chamber or hrood cTiamher. — The social chamber, as in Xyle- 

 iorus saxeseni, is a dilated portion of the tubelike gallery to accomo- 

 date all stages of the brood. 



Death chamber (catacomb or garbage chamber). — The death cham- 

 ber (Hubbard, 1897; also Hopkins, 1898) is a section in the social 

 chamber in which the dead individuals of the colony or the guests and 

 enemies as well as other refuse matter are deposited and separated 

 from the main chamber by a wall of the ambrosia fungus mixed with 

 boring dust. 



Entrance burrow. — The entrance burrow is made by one or the 

 other sex as a preliminary to the excavation of the egg gallery, and 

 may connect in a direct manner or laterally with the base of the gal- 

 lery in the case of single galleries, or with the middle in the case of 

 double galleries. 



Nuptial (lateral or central) chamber. — The nuptial chamber is 

 excavated by one or the other sex (probably in most cases by the 

 male) at the base of the entrance burrow and the mouth of a single 

 or many egg galleries. In Pityophthorus, Ips, etc., this chamber is 

 short and broad, oblong, or rectangular. In some species of Scolytus, 

 Phlceophthorus, Hylesinus, etc., the lateral entrance appears to serve 

 the same purpose as the nuptial chamber, while in Phloeosinus the 

 chamber is at the base of the egg galleries and entrance burrow and 



