34 . NORTH AMERICAN DIPTERA 



length of about 2 millimeters (as DasymoJophilus) to gigantic forms 

 with a wing-length in excess of 45 millimeters {Ctenarroscelis). 



Rostrum sometimes greatly elongated, in some {Elephantomyia: 

 Toxorhina) produced by a great lengthening of the front, the reduced 

 mouthparts being at the extreme tip; in others {Limonia: Geranomyia) 

 the similarly greatly lengthened mouthparts consist chiefly of the labial 

 palpi. In most Tipulidae the rostrum is short to very short. In many 

 TipulinaB it is further tipped by a small nose-like point, the nasus. Max- 

 illary palpi ranging in number of segments from 1 (some Limonia and 

 Hexatoma: Conosia) to the normal number of 4. Antennae ranging 

 in number of segments from 6 {Hexatoma) to 39 {Gynoplistia: Cero- 

 zodia) ; sometimes very greatly lengthened in males, being one or more 

 times the length of the entire body {Megistocera: Macromastix; Hexa- 

 toma: Eriocera; Eliahdomastix) ; sometimes with branched flagellar 

 segments (many Tipulina^; some Cylindrotominae; a few Limoniinge, as 

 Limonia: Rhipidia and Gynoplistia) ; pedicel shorter than scape (except 

 in some Eriopterine Claduraria) ; sometimes the basal flagellar segments 

 united into a fusion-segment (Claduraria, Toxorhinaria). Eyes with 

 ommatidia variable in size and coarseness; sometimes lioloptic (Li- 

 monia), usually broadly dichoptic. Pediciini with short erect set^e 

 between ommatidia. 



Pronotum sometimes lengthened (some Limonia, Toxorhina) . Prae- 

 seutum sometimes produced cephalad over pronotum {Conosia, T rente - 

 pohlia) . Paired doul)le dots, tlie tuherculate pits, often present, one on 

 either side of midline on ee])halic half of pr^escutum. PseudosiituraJ 

 foveae often present as shiny depressions on humeral portion of prip- 

 scutum. Postnotal pleurotergite sometimes produced into a tubercle 

 (some Tipulinje). Halteres long to very long. Legs with trochanters 

 short, rarely lengthened {Atarha, Rliahdomastix) ; tibiae with or without 

 terminal spurs; claws simple or variously toothed {Limonia, Tipula). 

 Wings of various shapes, sometimes long and narrow, the anal angle 

 correspondingly reduced (some Limonia), sometimes with the region 

 squarely developed {Antocha) . In cases, a pale longitudinal fold in 

 cell Cu of wings (DicranoptycJia) . The details of venation are not 

 discussed here, having been thoroughly considered by the present writer 

 in recent papers that are cited in the morphological bibliography at 

 end of paper and which may be consulted for details. The chief premise 

 of the interpretation of the radial field is that the so-called radial cross- 

 vein, r, of the Comstock-Needham system, has never been developed 

 in the Diptera, the vein that has been so interpreted in the few families 

 where it is found being the transverse free portion of R.,- The anterior 

 branch of the radial field is labelled P^o' except in tlie su])tri])e Limoni- 



