416 PROCEEDINGS OF THE NATIONAL MUSEUM. vol.54. 



Epistemum. — The episternum is a well-defined, always closed 

 area, beginning at the base of the wing, usually longitudinally elon- 

 gate, and always inferior to the pleural suture. It is sometimes 

 bilobed with a large lobe extending forward to the front of the ster- 

 num and with the alar lobe smaller and acute, as in Triozocera mexi- 

 cana (pi. 65, fig. 7). The episternum is much broader in Del- 

 phacixenos anomaloceriis^ but is bilobed. The episternum proper is 

 the lobe to the wing; the inferior lobe is the lateropleurite. The 

 episternum never reaches the coxal area in the strepsipterous meta- 

 thorax and in this it greatly differs from most orders of insects (pi. 

 64, fig. 2; pi. 65, fig. 7; pi. 66, figs. 3, 7; pi. 69, fig. 2; pi. 70, figs. 2, 4; 

 pi. 72, fig. 1 ; pi. 75, fig. 2 ; pi. 76, fig. 5 ; pi. 78, figs. 3, 7) . 



Sternum. — The Strepsipterous sternum is a large area without dis- 

 tinct sutures but always having a strong median longitudinal chiti- 

 nization behind. This chitinization divides the sternellum into two 

 parts. The sternellum (furcasternite) is transversely separated from 

 eusternum (basisternite) in front of it, mereby by a faint line, which 

 is sometimes distinct at the sides, where it branches from the pleural 

 suture. The anterior area or presternum is also indistinctly separated 

 by a faint line (pi. 64, fig. 2; pi. 65, fig. 7; pi. 66, fig. 2; pi. 69, fig. 3; 

 pi. 74, fig. 2 ; pi. 75, fig. 3 ; pi. 76, fig. 5 ; pi. 77, fig. 4) . 



Sternellum. — The sternellum, as has been said before, is sometimes 

 fused with epimeron. It usually also contains the precoxale and 

 trochantin. It is always, however, distinctly separated from the 

 coxa, to which the trochanter is loosely articulated. 



Postcoxale. — In Tetrozocera a tiny strip continuing from epimeron 

 passes behind the coxa (pi. 66, fig. 2). 



Poststernellum. — In Tetrozocera there is also a small piece between 

 the coxae, which is probably the poststerellum (postfurcasternite) 

 (pi. 66, fig. 2). 



Ahdomen. — The Strepsipterous abdomen contains 10 segments, of 

 which the first two or three are usually greatly interrupted or 

 crowded dorsally and ventrally, but normal laterally between the 

 postscutellum and the hypoepimeron (called femoralia by early 

 writers). The first abdominal spiracle occurs near the anterior mar- 

 gin of the first segment near the lower pleurotergite of the meta- 

 thorax (pi. 64, fig. 7; pi. 65, fig. 9; pi. 66, fig. 3). The other spiracles 

 are usually difficult to find, but in Tetrozocera santchii there are 

 eight abdominal spiracles (pi. 66, fig. 3). 



The ninth segment is always ventrally produced beyond the tenth, 

 which is merely a little flaplike covering of the large concavity 

 made b}'^ the ninth. At the tip of the ninth is the oedeagus, a 

 chitinous unpaired median tube with a subapical pore for the exertion 

 of the penis. This oedeagus rests in the depression of the ninth and 

 is apically covered by the flap of the tenth segment. The shape of the 



