Diptera. 61 



ORDER DIPTERA 



(ANTLIATA, HALTERATA, HALTER1PTERA, 

 HAUSTELLATA.) 



Minute to moderate-sized, rarely large insects, usually with 

 good powers of flight; the hind wings replaced by small knobbed 

 structures (halteres): head usually vertical, freely movable; 

 antennae variable, frequently three- jointed and provided with a 

 sensory bristle (style or arista); mouth-parts suctorial; both the 

 prothorax and metathorax small and fused with the large meso- 

 thorax; wings membranous, veins and crossveins not numerous; 

 legs usually alike, the tarsi regularly five-jointed. Metamor- 

 phosis complete, the larvae almost always legless grubs or maggots, 

 frequently with the head retracted and indistinct; pupae with the 

 appendages more or less adherent, the body sometimes entirely 

 encased in a seed-like capsule (puparium) . Food-habits variable. 

 Flies, Mosquitoes, Gnats, Midges. 



1. Antenrue generally longer than the thorax, usually composed of from eight to 



sixteen free joints (PI. 12, figs. 262, 266, 272) and rarely with a differentiated 

 style or bristle; anal cell widely open, rarely narrowed in the margin of the 

 wing, discal cell usually absent, second vein often forked; calypter absent; 

 palpi usually elongate, hanging downward and comprising four or five joints; 



body very rarely with bristles. (NEMATOCERA.) 2 



Antenna? usually three-jointed, the third joint however often complex (PI. 12, 

 fig. 283) or bearing a differentiated style (PI. 12, fig. 300) or arista (PI. 12, 

 fig. 301) ; anal cell distally narrowed or closed, sometimes very short or even 

 absent, discal cell usually present, second vein never furcate; palpi short, 

 projecting forward, never with more than two joints. (BRACHYCERA.) . 17 



2. At least nine veins reach the margin of the wing, discal cell often present, second 



and fourth veins forked 3 



Less than nine veins terminate in the margin of the wing, no discal cell 9 



3. Costa continuing around the hind margin of the wing; ocelli almost always 



wanting 4 



Costa much thinned beyond the tip of the wing; a single pad between the tarsal 

 claws; ocelli present; males holoptic; wings usually spotted. (Rhyphus, 

 Olbiogaster) (PI. 12, figs. 276, 288) (ANISOPID^E, PHRYNEIDffi). 



RHYPHID./E 



4. Veins bare or nearly so, if hairy the mesonotum has a V-shaped suture; legs 



very long and slender; body and wings elongate; males dichoptic, i. e. the 



eyes not meeting above 5 



Veins, including the hind margin, very hairy or scaly; body hairy or scaly; 

 mesonotum without a transverse suture ... ... 6 



