180 



IMAGINES 



1. Antenna consists of a 2-jointed scape — the basal joint usually indis- 



tinct — and a distinctly segmented flagellum of more than 2 joints 

 ORTHORRHAPHA, pt. 



— Antenna consists of apparently 2 or 3 joints and, usually, a ter- 



minal or dorsal arista 2 



2. Frontal lunule absent ORTHORRHAPHA, pt. 



— Frontal lunule present, or if poorly developed or apparently absent 



there are no distinct cross-veins on disc of wing 



CYCLORRHAPHA. 



Suborder ORTHORRHAPHA 



Keys to Divisions 



larvae 



1. Head complete, or sometimes incomplete posteriorly ; mandibles ab- 

 sent or vestigial in Cecidomyiidae, but the body consisting of 13 

 segments in addition to the head, in other families mandibles 

 present, moving horizontally or nearly so, their position when at 

 rest being on a horizontal plane, or varying but slightly from it, 

 their apices opposed ; labium usually well developed, in the form 

 of a flat plate with or without dentate anterior margin ; larvae 

 frequentlv peripneustic, the aquatic forms usually with protrusive 

 anal blood-gills NEMATOCERA (p. 182). 



— Head always incomplete and partly retracted within the prothorax ; 



mandibles moving vertically, their position when at rest vertical, 

 the apices parallel and directed downward ; labium poorly de- 

 veloped, rarely or never in the form of a flat plate ; larvae nor- 

 mally amphipneustic or metapneustic, very rarely peripneustic, 



aquatic forms without protrusive anal blood-gills 



BRAOHYCERA (p. 307). 



PUPAE 



1. Head, except in some Cecidomyiidae and a few Tipulidae, without 

 strong thorns; antennae much elongated, always very distinctly 

 traceable, normally curved well over upper margin of eyes and 

 extending to or beyond base of wing, in some cases almost to apex 

 of wing; thoracic respiratory organs much elongated or sessile; 

 legs of variable length, often extending to apex of abdomen, rarely 

 slightly longer than wings, in aquatic forms often recurved against 

 base of abdomen ; abdomen in species with short antennae some- 

 times unarmed NEMATOCERA (p. 182) . 



— Free except in Stratiomyiidae ; head in other families usually with 



