OF WASHINGTON. 99 



(CxP), bearing the dorsal coxal articulation. The coxal pro- 

 cess is absent as a distinct arm in the metathorax of Coleoptera 

 and of Spongophora (Euplexoptera), but the same pleural sur- 

 face articulates with the coxa. The pleural ridge generally gives 

 off internally a pleural apodeme {PA) which frequently unites 

 with a corresponding apodeme from the sternum. All insects 

 possess these parts or rudiments of them. Verhoeff uses the 

 names anopleure and coxopleure to designate the two main 

 pleural plates of the lower insects on the ground that they may 

 not be homologous with the epimerum and episternum of the 

 higher insects, but a complete uniformity can be traced in these 

 parts throughout all insects. 



In many of the lower insects a large plate {K) occurs an- 

 terior to the episternum and generally between the latter and 

 the sternum. It has been termed the katopleure by Verhoeff 

 and this name will be used in the present paper. The kato- 

 pleure is well developed in the Blattidae, the Mantidae, and in 

 the mesopleurum of the Euplexoptera, but in most other forms 

 it is either rudimentary or absent or is fused with the epi- 

 sternum. 



A very important pleural plate of the lower insects is the 

 trochantin (T). This sclerite lies between the episternum and 

 the coxa and its ventral end forms a second or ventral point of 

 articulation of the coxa with the body. Hence, those insects 

 possessing a well-developed trochantin have the coxa articu- 

 lating to the trunk by a simple hinge joint, and its movement is 

 thus limited. Amongst the Orthoptera the trochantin is well 

 developed in the Blattidae (figs. 3 and 8), the Mantidae (figs. 2 

 and 4), the Locustidse, and the Gryllidse. It is absent as a 

 functional sclerite in the Acridiidae and here the coxa can rotate 

 freely upon the coxal process as on a pivot. The trochantin is 

 large in Euplexoptera. In the Coleoptera it is present only in 

 the prothorax and the mesothorax. It is always small, some- 

 times fused with the coxa, and is generally concealed within 

 the coxal cavity. 



Lying between the trochantin and the coxa are often one or 

 two small accessory plates. The one more closely associated 

 with the trochantin may be termed the accessory trochantin 

 plate (figs. II and 12, T. a) and the other the accessory coxal 

 plate (figs. 9, 10, and 12, Cx. a). An accessory plate fre- 

 quently Hes also at each anterior angle of the sternum (figs. 

 9, 10, 12, and 13, S. a). This is called the vorplatte by Ver- 

 hoeff and other German entomologists. 



Nearly all winged insects, in addition to the above, have one 

 or two plates at the dorsal end of the episternum connected 



