1916] Thoracic and Cervical Sclerites of Insects 49 



Verhoeff, '02-'04, Voss, '04, and Snodgrass, '09, have proven 

 conclusively that the tergum is composed of but two plates, the 

 scutoscutellum (Crampton, '09) and the postscutellum (Audouin, 

 '24), the latter being absent in the pronotum, (Fig. 13, scsl, psl). 

 The anterior plate or scutoscutellum is generally marked off by 

 transverse sutures into three regions, the prescutum, scutum 

 and scutellum, but sometimes the sutures which mark the 

 boundaries of these regions are absent( Fig. 13, prsc, sc, si). In 

 many insects the posterior plate or postscutellum is divided 

 longitudinally into a median and two lateral regions, which 

 may be subdivided (Fig. 1, psl). Crampton, '09, termed these 

 regions the mediophragmite or median region and pleuro- 

 phragmites or lateral regions. I shall use the terms medio- 

 tergite and pleurotergite for these regions, because they are 

 subdivisions of the tergum (Fig. 1, mt, pit). When they are 

 further subdivided by a transverse suture, Crampton, '09, refers 

 to the subdivisions as the superior and inferior region of their 

 respective medio- or pleurophragmite (medio- or pleurotergite). 

 I shall refer to the subdivisions of the medio- and pleurotergite 

 in the same manner (Fig. 1, spplt, iplt). In Tipula the pleuro- 

 tergite is divided transversely into the superior pleurotergite 

 and inferior pleurotergite (Fig. 1, spplt, iplt). In other Diptera 

 such as Leptis, Tabanus, etc., the pleurotergite is subdivided by 

 a longitudinal suture into the outer and inner pleurotergite 

 (Figs. 2 and 11, oplt, inplt). Crampton, '09, previously used 

 these adjectives to designate the outer and inner "pleuro- 

 phragmite." 



The scutellum projects laterally on both sides, until it meets 

 the posterior margin of the wing. (Fig. 1, si). The prescutum 

 and postscutellum are often continued laterally on either side 

 until they join the pleuron, although frequently these lateral 

 prolongations become much reduced in size or split up into 

 smaller pieces (Fig. 2, prsc, psl). Projecting internally, some- 

 times from the anterior margin of the tergum, sometimes from 

 the posterior margin, or from both, is a process termed the 

 phragma, which serves for the attachment of muscles. When 

 the phragma is attached to the anterior margin of the tergum, it 

 is termed the prephragma and when attached to the posterior 

 margin, is termed the postphragma (Snodgrass, '10). The 

 prescutum and postscutellum are frequently represented in the 



