prelimixaky classification" of scolytoidea. 201 



Galleries. 



There is a wide variation in the t}^Des or forms of the egg and brood 

 galleries within the families, subfamilies, and the major and minor 

 groups, and m some cases within the genus. Each species or group of 

 allied species of a genus or group of allied genera is usually character- 

 ized by some peculiar form or feature which m many cases is sufficent 

 in itself to indicate the species, genus, or group to which it belongs; 

 therefore the galleries are of special taxonomic importance m indicat- 

 ing the natural position and grouping of the species and genera. 



It has been supposed that a peculiar type of gallery was due to 

 the character of the plant tissue in which it was excavated or that it 

 had some relation to the species of plant. It is found, however, that 

 the type of the gallery is the same, or similar, for the same species, 

 regardless of the character of the substance or the species of plant in 

 which it is excavated. In fact, the same species of spruce or pme, 

 and the bark on the trunk or branches, or the wood of the same part 

 of the tree, may have as mam' radically different tj^pes of galleries 

 as there are different species of beetles to make them. 



It has also been supposed that the type of a gallery was due to the 

 peculiar structure of the beetles, such as the refuse or concave and 

 armed elytral declivity in Ips, ascendmg or excavated abdommal 

 sternites of Scolytus, etc., but it is found that certain species with the 

 same or similar structures make very different t3'pes of galleries, 

 while certain other species with ver}-^ dififerent structures make similar 

 galleries. 



'The fact that there is quite a definite relation between the type 

 of the gallery and the systematic position of the species, genus, and 

 group would indicate that the evolution of the gallery has been from 

 the simple to the complex and that it has progressed with the evolu- 

 tion of the beetles that make and inhabit it m a somewhat similar 

 manner to that of the dommant tendency in the evolution of human 

 dwelling places from the simple cave to the modern palace. In other 

 words, the simple and comj)lex galleries represent evolution within 

 the maximum and minimum limits of an mstmctive or dominant 

 tendency connnon to all of the individuals of the superfamily Scoly- 

 toidea and are expressed by each species of a genus in the varymg 

 degrees of simplicity or perfection accordmg to the varying stages 

 in the evolution of the species. 



Tlie fact that the same or a similar type of gallery is made by 

 species of widely separated genera and subfamilies mdicates that 

 we should not look for an explanation of the origin and evolution of 

 types of galleries m the phylogeny of the species, but that a thorough 

 consideration should be given to the explanation to be found m paral- 



