10 G. C. Crajipton aud W. H. Hasey, 



(Fig-. 16) as the ''trochanter", and interpreted the membranous region 

 between the true coxa and the pleural region, as the "coxa". 



The femur may be broadley joined to the apex of the trochanter 

 (in which case, the line of union is transverse) or the femur may 

 be joined to the side of the trochanter (in which case the line of 

 union is oblique). These features are made use of in the classification 

 of the Coleoptera, and other insects. 



In the Myrientomata (Fig. 20) among- the Apterygota, and in 

 the Plecoptera (Fig. 21) among- the Pterygota, the trochanter, tr, is 

 reduced to a narrow ring above the femur. In some insects, the 

 trochanter may be broader than long, while in others it is longer 

 than broad. In the Carabidae, it is unusually large and well developed. 



In certain Hymenoptera, designated as the Ditrocha, the so- 

 called trochanter consists of two parts, a proximal and a distal 

 trochanter (Fig. 23, ptr and dir). The distal trochanter dtr is always 

 very closely connected with the femur, and is considered by many 

 as a poi'tion of the femur demarked by a constriction, while others 

 reg-ard it as a portion of the trochantin, which itself may be a 

 "constricted-off"' portion of the femur. In the larvae of certain 

 Odonata {Agrion) the trochanter appears to be marked oif into two 

 regions, and indications of a similar demarkation occur in the larvae 

 of certain Coleoptera (Dytiscus) and Trichoptera (Ithytrichia). A small 

 proximal region (not shown in Fig. 18) is marked off in the trochanter 

 of Machilis, but this does not seem to be entirely homologous with 

 the proximal region of the trochantin described in the above mentioned 

 insects. The views as to the homologies of the trochanter in different 

 arthropods will be discussed in the second part of this paper. 



Interpretations of other inresti gators. 



One of the most important of the earlier works dealing with 

 homologies of the parts of the leg of an insect, as compared with 

 those of other arthropods, is the article by Hansen, 1893. According 

 to Hansen, the trochantin (or the "pseudo-trochantin") of an insect, 

 is homologous with the coxopodite of the leg of a crustacean, while 

 the insect's coxa would be homologous with the crustacean's basi- 

 podite, etc. Henneguy, 1904, however, proposes the method of 

 comparison given in the appended table. 



