NO. 12 FT.YING APPARATUS OF BLOW-FLY RITTER I'J 



migium divides into three separate veins. The parts of these veins, 

 especially of Uaa and Illha, which are here still united, passing 

 through the flexible zone, are lighter colored than their other parts. 

 This lighter coloring is caused by the strong, dark chitin being here 

 restricted to narrow, transverse belts, separated by belts of similar 

 width, composed of weak and pale chitin (pi. y, figs. 20, 21, 22). 

 This portion of the vein is similar in structure to the ordinary 

 tracheae within the body, except that the strong and dark chitin does 

 not here form a continuous spiral band, but transverse belts or bars. 



5. The Articulation of the Wing 



(PI. 8, fig-s. 23, 24; pi. 9, figs. 25, 26.) 



The skeletal parts forming the articulation of the wing can be 

 divided into three groups : 



a. The thoracic parts (processus pterales thoracis), 



b. The intermediate parts (pteralia), and 



c. The alar parts (processus pterales alse). 



In naming these parts I have avoided all terms relating to form 

 or function and have designated them by letters and figures. I 

 selected for the processus pterales Roman figures, for the pteralia 

 capital letters, and for the processus pterales alas Arabic figures 

 (for example Proc. pter. al. i, etc.). This method is more practical 

 than the application of the terms used for analogous, but in no way 

 homologous, parts of the vertebrate skeleton to the insect skeleton. 

 In certain cases where I have either been able to ascertain the func- 

 tion of a part, or where its form is so striking that it easily im- 

 presses itself upon the memory, I propose to substitute, for better 

 orientation, instead of the above-mentioned designations, short terms 

 such as calyx, strom.a, etc. For the processus pterales thoracis I and 

 II the well-founded, older names processus prsealaris and postalaris 

 will be retained. Besides the parts belonging to the above-mentioned 

 groups there are others found in the articulation of the wing which 

 may be designated as stays. 



A. the thoracic portion (processus pterales thoracis) 

 This portion consists of six pieces : 



I. Processus pteralis thoracis I (Processus prsealaris) (pi. 2, figs. 

 3, 4 ; pi. 8, fig. 24 ; pi. 9, fig. 25, pti) . 

 Described above with the scutum. 



