2 DIPTERA. 



Diptera et Aptera p.: Linnaeus, 1753; Geoff roy ; Miiller ; Olivier 



Cuvier ; Duineril ; (Meigeu ; Fallen ; Zetterstedt.) 

 Halterata et Pedestria p. -. Scopoli, 1763. 

 Muscoides et Oniscoides p . -. Laicharting, 1781. 

 Halteriptera et Rophoteira p. : ClairviUe, 1798. 

 Biptera et AntennkUa p. : Rafinesque, 1815. 

 Aptera et Biptera p. : Lamarck. 



Angioptera p. : Linnaeus, 1735. 



AntVmta p. ai Rymjota p.: Fabricius, 1775; lUiger. 



Diptera et Aptera p. : Aristoteles. 

 Bipennia et impennia p. : Fliniiis. 

 Auelytra bipennia, &c. : Lister. 



MoutJi suctorial ; witli a proboscis, or sheath, closed on the under- 

 side (Labium), usually shut above by a slighter piece (Labrum), and 

 enclosing (generally an odd number of) lancets, varpng between one and 

 five, (Lingua, MaxiUae, Mandilnda3 :) a pair oi palpi (maxillary); rarely 

 there are the rudiments of another paii- (labial), or there are noue at all. 

 Sometimes the mouth is obsolete, or even closed. 



Thorax compact ; prothorax very short, immovably attached to the 

 mesothorax, which is the largest segment. 



A pair of icings (the anterior), the membrane not clothed with 

 scales ; divided into a moderate number of areolets, by interlaced veins ; 

 the base of the wing continued, more or less, in sinuous folds (Alidae), 

 below the sides of the scutellum. A pair of small clavate appendages, 

 filled with air (Halteres), behind them, in place of the posterior wings. 



Sometimes the wings, or both wings and halteres, are wanting. 



Tarsi pentamerous, rarely tetramerous.* 



No nipping jaws ; no wing-cases. 



This order is not liable to be confounded with almost any 

 other, as regards the winged species, which form the vast majority. 

 Only the male Coccidce, when they have compound eyes (some 

 Borthesice, &c.), resemble Chironomida, with the proboscis ob- 

 solete ; but their tarsi, of one joint and with a single claw, are 

 sufficient to distinguish them. The very superficial resemblance 

 which some Neuropteea {Cloiion spp. &c.), wanting the hind 

 wings, bear to dipterous insects, is not likely to mislead : these 

 have not halteres, and both the shape and the veining of the 



* Only two instances are recorded, viz., Bicera furcata (Germar), in which the 

 posterior pairs, and Echitiomyia teiramera (Zctt.), in wliich all the tarsi, are tetra- 

 merous. 



