36 Annals Entomological Society of America [Vol. IX, 



The homologies of the thoracic sclerites have been greatly 

 confused, owing to the fact that most investigators have given 

 their own views, without first giving sufficient study to the 

 work and terminology of previous writers. This has resulted 

 in the invention of new terms and the misapplication of those 

 already in use. Both the old and new terms have often been 

 applied to identical sclerites and consequently the terminology 

 is also in a chaotic condition. 



Some of the more recent writers have attempted to show the 

 unity of thoracic structure, which exists in all insects and to 

 introduce a terminology which will be as uniform as possible. 

 This is a very difficult task to accomplish because of the great 

 confusion which exists. 



In this paper an attempt is made to help straighten out the 

 homologies and terminology of the thoracic sclerites of insects. 

 An effort has been made as far as possible, to use the terminology 

 most widely accepted and which has the right of priority. 

 Where recent terms have been applied to sclerites, for which 

 the old terms seem inadequate or undesirable, the new terms 

 have been adopted. In some cases entirely new terms have 

 been applied to sclerites, but only where the condition of the 

 terminology seemed to warrant such action and where, in the 

 opinion of the writer, an improvement could be made. 



Especial attention has been given to a study of the pleuron 

 and sternum. The tergum and wings have not been investi- 

 gated so thoroughly and consequently a discussion of these parts 

 is not given in detail. All the specimens were studied under a 

 liquid medium (water, alcohol or glycerine), with the aid of a 

 Zeiss binocular microscope. A bull's eye condenser was used to 

 concentrate the rays of an electric light upon the object under 

 study. In many cases the specimens were first boiled in 10% 

 potassium hydroxide. The internal tissues were then washed 

 out with running water, thereby making the sclerites show up 

 clearly and leaving the internal processes intact. This pro- 

 cedure greatly facilitated the determination of the thoracic 

 sclerites and their sutures. 



