38 A^mals Entomological Society of America [Vol. IX, 



terms which seem to have been first used by Nitzsch, '18, 

 although Nitzsch called the first segment the protothorax 

 instead of prothorax. Audoiun regarded each thoracic segment 

 as made up of four parts; a dorsal region, the tergum; a ventral 

 region, the sternum; and two lateral regions, the pleurae. He 

 thought that the tergum was composed of four transverse sub-- 

 divisions, lying one behind the other in consecutive order. 

 Beginning with the anterior one, he termed these the prescutum, 

 scutum, scutellum and postscutellum. The sternum he regarded 

 as a single piece. For each lateral region or pleura he described 

 and named several pieces, viz. : two large lateral sclerites, the 

 anterior one termed the episternum and the posterior one the 

 epimeron ; a small narrow piece lying along the anterior edge of 

 the episternum termed "paraptere," (previously called "hypo- 

 tere" by Audouin, '20); a small sclerite containing the spiracle 

 termed the peritreme and a sclerite articulating with the 

 epimeron termed the trochantin. 



Audouin was mistaken in his definition of the last mentioned 

 sclerite, because the trochantin articulates with the episternum, 

 not with the epimeron. Later Audouin, '32, defined the "par- 

 aptere" as "the small piece so visible in Hymenoptera and 

 Lepidoptera, which covers the base of the fore wings and which 

 is variously designated by the terms ecaille, epaullette or 

 squamula." (Audouin's trans, of Mac Leay's paper, "The com- 

 parative anatomy of the thorax in winged insects, following a 

 review of the actual state of the Nomenclature." pp. 41, foot- 

 note by Audouin) . According to this statement the ' ' paraptere ' ' 

 is evidently synonymous with tegula. 



Subsequent entomologists in applying this terminology 

 for the thoracic sclerites have misinterpreted the homologies 

 and consequently confused the names. Several sclerites, which 

 Audouin apparently failed to recognize, have since been 

 described. In descriptions of these, different investigators 

 have invented new terms for identical sclerites, leading to more 

 confusion. 



In all insects there is a common ground plan, which is 

 more modified in some, less so in others. On this basis recent 

 writers have attempted to work out a uniform system of 

 terminology applicable to all insects. In order to do this, 

 it is first necessary to correctly homologize the sclerites in the 



