412 PROCEEDINGS OF THE NATIONAL MUSEUM. vol.54. 



coxae and tronchanter are apparently often fused. The coxa is never 

 more than a tiny basal piece of trochanter. 



Metathorax. — The metathorax is the dominant part of the body 

 of the male strepsipteron and is the part most characteristic of the 

 order as a whole. It differs most from other orders in the promi- 

 nence of the postlumbium throughout the order, and the unusual 

 development of the postscutellum. The pleural suture is almost 

 horizontal and longitudinal instead of vertical, as is usually found 

 in other orders. The posterior attachment of the Avings is ver}^ 

 distant from the lateral prolongation of the scutellum and if at- 

 tached at all the axillary cord is very long. 



In view of the fact that the metathorax has been illustrated for 

 each genus and fully described in the generic descriptions, this dis- 

 cussion will take up the various parts separately and trace their 

 modifications. 



Praescutum. — The anterior visible piece of the metanotum is the 

 praescutum. It is as broad as the scutum, and band-like as the pro- 

 notum and mesonotum in Mengea (Mengeidae) (pi. 64, fig. 1), large 

 and broad and not fully separated from the scutum in Trlozocera 

 (Mengeidae) (pi. 64, fig. 10; pi. 65, fig. 1) ; suppressed as a neck in 

 Tetrozocera and Austrostylops (Mengenillidae) (pi. 66, figs. 1, 5) ; 

 raised to the disk but narrower than scutum in Mengenilla (Men- 

 genillidae) (pi. 66, fig. 6). In these two families which form the 

 Mengeoidea the praescutum lies entirely in front of scutum and 

 scutellum and does not in any way push backward. 



In the remaining superfamilies the praescutum lies between the 

 lobes of the scutum and its anterior line is more or less continuous 

 with the anterior line of the scuti. In Myrmecolax the scuti some- 

 what constrict the praescutum before its posterior apex, but in 

 Caenocholax^ also of the Myrmecolacidae, this piece is semioval 

 (pi. 69, fig. 1). In both genera of Myrmecolacidae it is longer than 

 broad. 



In Xenidae the praescutum varies but little, being, either semilunar 

 or keystone-shaped and broader than long (pi. 72, fig. 2). 



In Diozocera (Diozoceridae) it is oblong, and in all Halictophagi- 

 dae it is longer than broad, varying more or less in shape from 

 oblong in Anthericomma and semielliptical in Pentozoe to pyriform 

 in Pentozocera. 



In Elenchidae it is elongate, very greatly narrowed behind (Deine- 

 lenchus) and sometimes constricted (Liburnelenchus). 



Scutum. — This part is the next transverse dorsal sclerite behind 

 the praescutum, but in most Strepsipterous genera would not be 

 recognized as transverse. It is alwa5's strongly lobed. Normally 

 the two lobes are connected behind the praescutum and in front of 

 the scutellum, but this connection is only to be found in a few 

 "■enci-n : 



