DIPTERA. 



The DiPTERA are usually separated into two great Suborders, which are 

 called 



DIPTERA ORTHORRHAPHA 



and 

 DIPTERA CYCLORRHAPHA. 



These two suborders are almost equal in extent, and are distinguished 

 mainly by the form of their pupse, though other characters exist both in 

 the imaginal and larval stages whereby they can be differentiated. 



The distinguishing characters of these two great suborders have been 

 given in the volume which dealt with the Syrpiiid^, and it is therefore 

 only necessary to deal with the Orthorrh apiia in this volume. 



DIPTERA ORTHORRHAPHA. 



The ORTHORRHAPHA fall naturally into two great divisions, which are 

 known as Orthorrhapha Nemocera and Orthorrhapha Brachycera. 

 These two great divisions are so distinct that Osten Sacken considered 

 each of them to be a suborder equal in rank with the Diptera Cyclor- 

 rhapha, and in confirmation of this opinion it may be noted that practically 

 all the writers before the recognition of the suborders Orthorrhapha 

 and Cyclorrhapha used to separate the Diptera into the Nemocera and 

 Brachycera. It would therefore be only necessary, after excluding the 

 Cyclorrhapha, to restore the Beachyceua to their old rank ; and then 

 (if three suborders of ef[ual rank were accepted) they might well be 

 called the Nemocera * (I'/'/^a, thread, and /ce'pa?, horn), Brachycera 

 (^paxv?, short, and Kepa^, horn), and Athericera {aOi'jp, awn, and Kepa?, 

 horn). 



* More correctly Xf.matocera, but antiquity and universal use sanctify the name. 



A 



