2 G. C. Crampton and W. H. Hasey, 



paper. For the sake of uniformity, however, all of the drawings 

 have been made by Mr. Hasey alone. 



When the two writers of the present paper were not in accord 

 as to the interpretation of the sclerites, the opinions of both have 

 been given; otherwise, the views herein expressed, are those which 

 have appealed to both alike. 



The articTilatiou of the leg. 



In comparing- together the sclerites of different insects, it is 

 necessary first to establisli certain fixed points, or "landmarks", 

 whose position is constant throughout the entire series. The homo- 

 logies of the various sclerites may then be readily determined by 

 the relation they bear to the landmarks in question. 



Four such landmarks of importance in the study of the basal 

 sclerites of the leg, are as follows. 1. The pleural suture 

 (Figs. 2, 3, 4, 8, etc., g) extending from the top to the bottom of 

 the pleural plate, and separating the episternum, es, from the 

 epimerou, e7n. It is continued downward into the coxa as the coxal 

 suture, 7, which divides the coxa into an anterior and posterior 

 region, vc and me. 2. The pleural fulcrum of the coxa 

 (Fig. 9a), or projection of the pleural plate at the bottom of the 

 pleural suture, serving as a pivot, or fulcrum, in the movements of 

 the coxa. 3. The apex of the troc h antin (Fig. 9b), which may 

 likewise serve as a pivot, or fulcrum, in the movements of the 

 coxa, when the trochantin is immovably united with the lower 

 portion of the pleural plate; but when the trochantin, or its terminal 

 portion, remains detached to form a distinct, movable plate, it is 

 probable that it then acts merely as a point of attachment for certain 

 muscles moving the coxa. 4. The sternal fulcrum of the coxa 

 (Fig. 9c), or projection of the sternal region forming a pivot, or 

 fulcrum, in the movements of the coxa. This projection is usually 

 absent in the lower insects, but is well developed in the higher 

 forms, such as the Neuroptera, Trichoptera, Lepidoptera, Diptera, etc. 



The trochantin. 



One of the most important of the articulatory sclerites at the 

 base of the leg, is the trochantin, or trochantinus. Since this 

 sclerite has been the subject of such diverse interpretations by 

 different investigators, it may be of some interest to establish its 

 true identity. In its most characteristic form, the trochantin occurs 



