1916] Thoracic and Cervical Sclerites of Insects 43 



Raphidia and he was the first to suggest the possibiHty of the 

 occurrence of intersegmental or "complementary segments." 

 This is not supported by embryology, however, which gives no 

 indication of "complementary segments." Larvas frequently 

 acquire secondary adaptative structures, which cannot be con- 

 sidered as a retention of the primitive condition and the "com- 

 plementary segments" of the above mentioned larvae are prob- 

 ably some such secondarily acquired structures. Kolbe's 

 theory needs more proof to support it than the presence of sec- 

 ondarily marked off regions in larvae. A dissection of the larva 

 of a beetle in which there are present "complementary seg- 

 ments" identical with those described by Kolbe in the larva 

 of Lampyris demonstrates the following facts: that the "com- 

 plementary segments" have no segmental muscles or other 

 segmental structures; that the "complementary segment" is 

 apparently a fold of the sternal integument and does not extend 

 to the tergum ; that it belongs to the segment in front of it and 

 that each actual segment is marked off by an internal ridge, 

 which extends completely around the body and has longitudinal 

 segmental muscles connecting one ridge with the next. These 

 three ridges probably define the three thoracic segments. 



Walton, '00, is the exponent of another double subsegment 

 theory which is similar to Banks'. He considers the coxa in the 

 Hexapoda and Chilopoda as the fusion product of the appen- 

 dages of two primary metameres which he terms, "coxa genuina" 

 and "meron." The meron represents the rudimentary appen- 

 dage of the posterior metamere, which articulates with the 

 epimeron, and the "coxa genuina" represents the basal leg seg- 

 ment of the functional appendage of the anterior metamere, 

 which articulates with the episternum and has persisted. From 

 this he concludes that each segment is composed of two 

 metameres. Walton's idea that the meron represents a vestigial 

 leg is as improbable as Banks' view, that the styli of Machilis 

 were the vestiges of legs. There is no embryological evidence to 

 support Walton's theory and he has since repudiated it. 



Comstock and Kochi, '02, think each thoracic segment is 

 composed of two subsegments, which have become fused 

 together. The line of division between them is represented in 

 the tergum by the suture between the scutum and scutellum, in 

 the pleuron by the pleural suture and in the sternum by the 

 f ureas. 



