32 PROCEEDINGS OF THE ACADEMY OF [Jan., 



been here adopted. A narrow marginal area, the "coximarginal" 

 sclerite, is frequently separated from the rest of the coxa by a suture, 

 as is well shown in the Blattidae (pi. Ill, C m ), Corydalis (fig. 17), etc. 

 It is questionable whether this region corresponds to the area desig- 

 nated as " C m (?) " in fig. 18 of the Trichopteran thorax, but the matter 

 is of relatively slight importance. 



That portion of the furci-sternum later spoken of as the pedal region 

 (fig. 18, S 3& ) frequently occurs as an elongate wedge-shaped process 

 extending into the coxal region. In such cases the furci-sternum is 

 so closely connected with the coxal region that the coxa usually loses 

 much of its freedom of motion. This loss, however, is usually compen- 

 sated by the greater mobility of the trochanter. Although the tro- 

 chanter appears to consist of but one joint in many insects, the second 

 joint is frequently hidden within the coxa, so that the "ditrochleate" 

 condition is much commoner than is generally supposed. This fact has 

 led to the formulation of the theory that one of the segments of the 

 trochanter represents a second joint of the "meral" leg. As the 

 author of this theory has not yet published his results, the improbability 

 of such a hypothesis will not be discussed here. 



The question as to whether or not the trochanter (or any part of it) 

 is the upper portion of the femur, and the different theories regarding 

 its homology, have but little bearing upon a study of the thoracic 

 sclerites, and need not be further gone into here. 



The Sternum. — MacLeay, '30, as has been stated, proposes that 

 each segment is composed of four subsegments or annuli. Arguing 

 from the fact that the tergum.is divided into four regions, he states 

 that the sternum likewise "ought to be" divided into four regions, 

 and proposes for these the names prsesternum, sternum, sternellum, 

 and poststernellum. He has not figured, described or even seen these 

 regions, but merely assumes their existence because of the condition 

 found in the tergum. Indeed, Newport, '39, who adopts MacLeay's 

 theory, states that these regions cannot all be found in any living insect, 

 as the specialization and fusion of the subsegments have gone too far 

 to leave any traces of the subdivisions in the sternum. 



Despite Newport's statement to the contrary, four distinct sub- 

 divisions of the sternum are to be found in certain insects, as for exam- 

 ple in the thorax of Nemura (pi. I). The terminology proposed 

 by MacLeay has not been adopted for the following reasons: the 

 names presternum, siernum, sternellum, and poststernellum imply 

 a relation between these subdivisions of the sternum and the prse- 

 scutum, scutum, scutellum and postscutellum, as MacLeay intended 



