46 Annals Entomological Society of America [Vol. IX, 



What has been said of Kolbe's theory will also apply to 

 Henneguy's views. Henneguy's conclusions that Myriopoda 

 are the ancestors of insects and that the position of the spiracle 

 is to be explained by supposing that they were borne by the 

 hypothetical complementary segment must have a firmer 

 foundation before they can be accepted. Whether the spiracles 

 belong to the segment in front of them or to the segment behind 

 them is at present a disputed question. The spiracles are 

 usually absent in the prothorax. It certainly seems more 

 probable that the so-called complementary segments are 

 parts of the pro-, meso-, and metathoracic segments, since this 

 view is supported by embryology, anatomy, musculature, etc. 



Woodworth, '06, states that "theories of composite segments 

 in the thorax seem to be entirely untenable." He appears to 

 consider the thoracic segment as originally made up of a soHd 

 ring, which later becomes split in the following manner. The 

 development of the legs, results in the separation of the sternum 

 from the remainder of the segment; in the beginning of the 

 formation of the pleural suture; and of the suture which ulti- 

 mately separates the scutum from the scutellum. The develop- 

 ment of the wings results in the completion of the above 

 mentioned sutures; in the development of the prescutum and 

 postscutellum, and in the separation of the tergum from the 

 pleuron. Hence he concludes that the wings are not the 

 product of the pleuron or the notum, but are the means of 

 their differentiation phylogenetically and ontogenetically. 



Woodworth' s conception of the thoracic segment is no 

 longer accepted by most entomologists, although many originally 

 held the same view. In all primitive insects and in larvae the 

 sclerites arise as numerous islands of thickened chitin and not 

 as, a solid chitinous ring, which later becomes split up. In the 

 more specialized insects these small sclerites become more or 

 less fused together. This can be clearly demonstrated by 

 studying a series of insects beginning with larval and primitive 

 forms as Eosentomon, and gradually working up to the more 

 specialized groups. 



Berlese, '06, regarded each thoracic segment as originally 

 made up of a "tergite" and "sternite. " The "tergite" was 

 one solid piece which included the "alar sclerites, " the spiracles, 

 the tergum and the epimeron. The "sternite" is composed of 



