8 ILUXOIS BIOLOGICAL MOyOGKAPUS [8 



therefore, inharmonies, and perhaps suggesting improvements on the pres- 

 ent arrangement of the classification. 



In order to reach a correct estimate of the degree of speciaHzation of 

 the various parts of the head-capsule, an hypothetical type, representing 

 a supposed primitive condition, has been constructed. The structure of 

 this hypothetical type is based on the structure of the head-capsule of 

 generalized insects and of generalized adult and larval Coleoptera. Each 

 structure has been treated separately, starting from the hypothetical type. 

 The submentum has been included in this study because of its bearing on 

 certain developmental processes. All statements made refer to the species 

 listed under "materials" only. The material studied was soaked in a 10% 

 solution of potassium hydroxide until clarified, then washed in distilled 

 water to remove the hydroxide, and preserved in 70% alcohol. All dis- 

 sections were made under a binocular microscope in 70% alcohol in Syra- 

 cuse watch-glasses. 



