538 PROCEEDIXGS OF THE NATIONAL MUSEUM. vol.xxxvi. 



(1905) calls the preparaptera the " episternalgelenkplatten," and the 

 postparaptera the " epimeralgelenkplatten." These are excellent de- 

 scriptive terms but too cumbrous for translation into English or 

 Latin equivalents, and it is well to preserve the name " parapterum " 

 of Audouin. 



Either one or both of the episternal paraptera are connected with 

 the head of the costal vein of the wing by strong membrane, and upon 

 their inner surfaces are inserted the strong pronator wing muscles 

 by whose contraction the wing is turned forward upon the pleural 

 wing process and its costal or front edge depressed. In the higher 

 insects there is frequently only one preparapterum present and it 

 very commonly carries a large muscle disc on its inner surface which 

 forms the insertion of the pronator muscle. This whole structure is 

 called the '' appareil de pronation" by Amans (1885). The muscle 

 disc may be specifically designated as the pronator disc {PD). This 

 is not shown in the diagram, for it occurs mostly in the higher orders. 

 As examples of it see illustrations of the Euplexopteran metathorax 

 (98, 100, PD), the Coleopteran mesothorax ( 101, 129) , the Coleopteran 

 metathorax (110-121), and the Hymenopteran mesothorax (1G5). 

 In the Lepidoptera (154) the pronator disc (PD) is carried by the 

 upper edge of the episternum, but the parapterum (P) is also fused 

 with the latter. 



In the Coleoptera there is only one preparapterum present. In 

 the mesothorax it is usually represented by a small inconspicuous 

 plate or rod connected with the head of the elytrum and lying before 

 the wing process (102, 103, 105, 107, 108, P), only in rare cases does 

 it bear a pronator disc (101, 129, PD). In the metathorax, on the 

 other hand, the disc is always large and prominent (110-121, PD). 

 In Caloso7na scrutator (Carabidje) the parapterum and its disc (110, 

 113, P and PD\ are loosely articulated to the front of the wing 

 process {WP). In Dytixcus dauricus (Dytiscidsp) the parapterum 

 (114, 115, P) is closely articulated to the front of the wing process. 

 In Hydrophihis triangvlai^is (Hydroi^hilidte) the parai^tennn {P) 

 is fused with the base of the wing process (111, 112) and to the 

 anterior edge of a subdivision (eps) of the episternum {Eps). The 

 line of fusion, however, is easily seen. The same condition is found 

 in Melolontha vulgaris (Scarabandae) where the base of the parap- 

 terum (121, P) and the episternal subdivision {ejys) are closely 

 united. Finally, in such forms as Cyllene rohinuv (Cerambycida^) 

 and Dendroctonus valens (Scolytidse) these two parts (116, 118, P 

 and eps) are so entirely fused that the line of union is gone. Thus 

 in the higher beetles the appearance of two wing processes (118, P 

 and ^VP), caiTied by the episternum and epimerum, respectively, is 

 produced. The series of forms just described, hoAvever, shows con- 

 clusively that this condition is secondarily brought about through 



