186 



conceal the sternopleura and the scape of the antennae is almost 

 globose ; legs straight or recurved 8 



4. Legs short, apices of hind tarsi projecting slightly beyond apices of 



wings; antennae short, curved across middle of eye 



Bibionidae (p. 298) . 



— Legs elongate, usually all tarsi projecting for a considerable dis- 



tance beyond apices of wings ; antennae elongate, extending to or 

 beyond bases of wings 5 



5. Antennae almost straight, noticeably flattened, extending to bases 



of wings; thorax not much swollen in front, its anterior pro- 

 file not declivitous Platyuridae (p. 260) . 



Antennae distinctly curved, not flattened, extending beyond bases 

 of wings 6 



6. Thorax conspicuously swollen, almost globose, its anterior profile de- 



clivitous; sternopleura concealed Mycetophilidae (p. 248). 



— Thorax not conspicuously swollen, the anterior profile not declivi- 



tous 7 



7. Scape of antennae much swollen, globose ; abdominal spiracles small 



or absent; sternopleura remarkably enlarged, not concealed by 

 fore coxae and femora Chironomidae (p. 284) . 



— Scape of antennae not much swollen ; abdominal spiracles distinct ; 



sternopleura not visible, concealed by the large coxae and femora 

 of the fore legs Cecidomyiidae, pt. (p. 293) . 



SdARIDAE, pt (p. 258). 



8. Thoracic respiratory organs slender, long, and tube-like : legs 



straight, extending well beyond apices of wings ; body without 

 armature except a pair of hairs on anterior margin of head ; 



sternopleura concealed Cecidomyiidae, pt. (p. 293). 



Sciaridae, pt (p. 258) . 



— Species without the above combination of characters, abdomen 



usually with hairs or spines, or the sternopleura is exposed 9 



9. Pupa in a pocket- or slipper-shaped cocoon consisting of coarse 



threads, from the Avide, open extremity of which project the 

 thoracic respiratory organs, each of the latter consisting of 4 to 

 60 tube-like branches on a common base ; rarely the cocoon is a 

 mass of rather loose threads Simuliidae (p. 302). 



— Pupa free, or if enclosed or partly so the cocoon is not pocket-like 



and the respiratory organs do not consist of tube-like branches . 10 

 10. Pupa when seen from above oval in outline, the abdomen at base 

 not conspicuously narrower than thorax, so that the lateral outline 

 is continuous ; dorsal surface with very strong, almost chitinized, 

 membrane 11 



— Pupa with the abdomen well differentiated from thorax, the dorsum 



membranous, or if strong and almost chitinized, then with surface 

 spines 12 



