78 Annals Entomological Society of America [Vol. IX, 



" cephlo-sternum " to the ventral cervicals. Huxley, '85, 

 used the term cervical sclerites to designate the neck plates. 



Lowne, '90, considered the cervicals as detached portions 

 of the prothorax, thereby accepting the theory formerly pro- 

 posed by Newport, '39. 



Verhoeff, '02-'04, adopted and elaborated the theory 

 advanced by Straus-Durckheim, '28, viz., that the cervicals 

 represent two segments originally situated between the head and 

 prothorax. He termed the neck region the " microthorax " and 

 designated the various sclerites by the terms, " coxopleure, " 

 ''anapleure, " etc. This theory was severely criticized by 

 Silvestri, '02, Borner, '03, Voss, '04, Desguin, '08, and others. 

 They proved conclusively that Verhoeff 's " microthoracic " 

 theory was unsupported by anatomy, embryology, musculature, 

 etc. 



Berlese, '06, regarded the cervical sclerites as belonging 

 to the head and prothorax. 



Snodgrass, '08, adopted Verhoeff's theory of the "micro- 

 thorax," but later Snodgrass, '09, repudiates the "micro- 

 thoracic" theory, adopting the term "cervicum" of Crampton, 

 '09, for the neck region. 



SUMMARY. 



The thorax is composed of three segments, the pro-, meso-, 

 and metathorax. 



All compound segment theories are not based upon enough 

 facts to be acceptable at present. 



The thorax of primitive insects, larvae, etc., is composed 

 of numerous small sclerites, which become fused to form the 

 sclerites of the higher insects. 



A secondary fusion or a splitting of sclerites often occurs. 

 Certain specialized forms often retain some characters of 

 primitive insects. 



The tergum of winged insects is composed of two sclerites, 

 which are usually subdivided into regions. 



The wing articulates with two processes on the lateral 

 margin of the tergum and with the alar plates at the base of the 

 wing. Ventrally it articulates with the pleural wing process. 



The pleuron is represented by a single sclerite in some 

 primitive insects. {Eosentomon). 



