44 Ajinals Entomological Society of America [Vol. IX, 



This theory is open to the same objections as the other 

 compound segment theories previously stated, viz. : that embry- 

 ology gives no indications of compound thoracic segments. 

 Primitively the episternum and epimeron appear to consist of a 

 single plate, a portion of which has become drawn inward, 

 probably by muscular stress, forming a hollow infolding of the 

 integument, which is represented externally by the pleural 

 suture and internally by the lateral apodene. The anterior 

 sclerite formed by this infolding of the pleuron, is termed the 

 episternum, and the posterior sclerite, the epimeron. If this 

 explanation be true, Comstock's and Kochi's view, as well as 

 Banks' and Walton's idea which is very similar, namely, that 

 the pleural suture is the line of union between two subsegments, 

 must be regarded as untenable. 



VerhoefT, '02-'04, made an extensive study of the com- 

 parative morphology of the insect thorax and his conclusions 

 are based mainly on the thorax of the Chilopoda, Apterygota, 

 Orthoptera, Dermaptera and Embiidas. His theory is an 

 elaboration of the views advanced by Kolbe. In studying 

 Japyx, Verhoeff found in front of the "chief segments," rep- 

 resented by the pro-, meso-, and metathorax, indications of 

 three other segments, which he called complementary segments 

 and termed them micro-, steno-, and cryptothorax respectively. 

 Thus the thorax would consist of six primary segments viz., 

 micro-, pro-, steno-, meso-, crypto-, and metathorax. He 

 found, on further study, that in front of each of these six primary 

 segments were a few small sclerites, which he considered as 

 the remains of six other segments and termed them the inter- 

 calary segments. Hence according to Verhoeff the thorax 

 would consist of six primary and six intercalary segments, 

 making a total of twelve thoracic segments, or in other words, 

 each segment of the thorax consists of four annuli. This 

 theory has been severely criticized by several writers and now 

 is generally considered as incorrect. Silvestri, '02, and Borner, 

 '03, criticized Verhoeff's views and the latter shows by his 

 figures that Verhoeff's statements are erroneous. Borner 

 states that the thorax is composed of three segments with 

 intersegmental regions. 



Voss, '04, gives Kolbe's and Verhoeff's composite segment 

 theory, stating four possible modifications of it, which can be 



