178 CONNECTICUT GEOL. AND NAT. HIST. SURVEY [Bull. 



20. Apical veins strongly arched DIXIDAE 



Veins straight or nearly so CULICIDAE 



21. Fourth posterior cell widely open ANISOPODIDAE 



Fourth posterior cell closed RACHICERIDAE 



22. Empodium developed pulvilliform, the three pads nearly equal 23 



Empodium hair-like or absent 29 



23. Third antennal segment compound, composed of annuli 24 



Third antennal segment simple, usually hearing an elongated style or 



arista 27 



24. Squamae large and conspicuous TABANIDAE 



Squamae small or vestigial 25 



25. At least the middle tibiae with spurs COENOMYIDAE 



Tibial spurs absent 26 



26. Posterior branch of the third vein ending before the wing-tip. 



STRATIOMYIDAE 

 Posterior branch of the third vein ending well behind the wing-tip. 



PANTOPHTHALMIDAE 



27. Squamae very large; head very small, placed low down, composed 



almost entirely of the eyes, the face and front veiy narrow or oblit- 

 erated CYRTIDAE 



Squamae small; head larger, the face or front broad 28 



28. Middle tibiae with spurs; venation not complex RHAGIONIDAE 



Tibiae without spurs; venation intricate, many veins ending before the 



wing-tip NEMESTRINIDAE 



29. Wings rounded apically, with strong veins anteriorly and very weak. 



oblique ones; coxae not widely separated by the sternum.PHORIDAE 

 Wings with normal venation or pointed at the apex, or the coxae 

 broadly separated by the sternum 30 



30. Wings pointed at the apex, without crossveins LONCHOPTERIDAE 



Wings rounded at the apex almost always with crossveins 31 



31. Two or more submarginal cells, the third vein furcate 32 



Only one submarginal cell, the third vein simple 38 



32. Front hollowed between the eyes, strongly concave from anterior 



view 33 



Front scarcely or not at all concave from anterior view 34 



33. At most one ocellus; at most two veins reach the wing margin behind 



the apex rV.YDAIDAE 



Three ocelli; at least four veins reach the wing margin, or extend to- 

 ward it, behind the apex ASILI DA E 



34. Costa continuing around the wing; fourth vein ending beyond the 



wing-tip , - 35 



Costa not continued beyond the apex of the wing; fourth vein ending 

 before the wing tip SCENOPINIDAE 



35. Five posterior cells 36 



At most four posterior cells 37 



36. Fourth vein ending before the apex of the wing APIOCERIDAE 



Fourth vein ending behind the apex of the wing THEREVIDAE 



37. Anal cell open or closed near the wing margin, the anal vein reaching 



the margin BOMBYLIIDAE 



Anal cell closed far from the wing margin, the anal vein never ex- 

 tending to the margin, sometimes absent EM PI DAE 



38. Anal cell elongate, tapering and acute apically, closed near the border 



of the wing; basal cells usually elongate 39 



Anal cell short, transverse, oblique, or convex apically, if somewhat 

 pointed the apex partly transverse, partly drawn out into a trian- 

 gular point posteriorly 40 



39. Anal cell closed very close to the wing margin; a spurious vein run- 



ning obliquely between the third and fourth longitudinal veins. 



SYRPHIDAE 

 Anal cell usually shorter; no spurious vein 40 



