78 MISC. PUBLICATION 336, U. S. DEPT. OF AGRICULTURE 



28. Thorax with fine spicules (best observed toward sides) ; lateral hair 



of anal segment usually single; basal (or proximal) tufts of air tube 



usually double or long and single, occasionally triple G. nigripalpus 



Thorax glabrous; lateral hair of anal segment usually double, occa- 

 sionally single; basal tufts of air tube usually with three or four 

 branches, occasionally with two C. salinarius 



29. Pecten spines fringed on one side nearly to tip; ventral tufts of air 



tube long (those nearest base about twice diameter of tube or more), 



multiple and finely feathered Culex (MeJanoconion) 31 



Pecten spines with one to four coarse side teeth ; air tube with compara- 

 tively short tufts (little, if any, longer than diameter of tube). 

 [Air tube long, 6-7:1.] 30 



30. Head hairs long, usually single, the lower pair or both pairs occasion- 



ally double; air tube slightly expanded toward tip, with four or 

 five paired ventral tufts beyond pecten (none at base) ; comb a patch 

 of scales, the single scale rounded and fringed apically; body finely 



pilose C. apicalis 



Lower head hairs single, the upper ones shorter and multiple ; air tube 

 with a tuft of hairs at base and with a row of about 12 short, sub- 

 equal tufts on midventral line; comb a single row of long barlike 

 scales T. melanura 



31. Air tube long and slender, 5-6 : 1, with four to six pairs of ventral hair 



tufts beyond pecten 32 



Air tube short (about 3:1), with about eight pairs of very long hair 

 tufts, basal two within pecten. [Comb of eighth segment of 8 to 12 

 scales in a curved or irregular row, the single scales long and pointed, 

 unf ringed ; a stalked ovoid gill at base of antenna ; head hairs small, 

 usually single, upper ones sometimes double; thorax slightly spicular.] 



C. pilosus 



32. Lower head hairs single, upper ones shorter, double or triple ; body 



sparsely spicular; comb with the scales in a patch, each scale rounded 



and fringed apically; air tube slightly flared at tip C. peccator 



Lower head hairs long, single, upper ones short, multiple (four or 

 more) ; body usually densely spicular-pilose ; comb with one irregular 

 or partially double row of scales, the individual scales long and 

 pointed and fringed on basal half C. erraticus 



PSOROPHORA 



33. Mouth brushes formed of stout prehensile hairs (each hooked at tip 



and with a row of comblike teeth along the side) (fig. 25, D). 

 [Air-tube pecten with numerous teeth, which are prolonged into hairs ; 

 tuft of air tube a single long hair.] Very large predacious larvae — 34 

 Mouth brushes normal, ciliform. [Pecten with a few strong, widely 

 spaced teeth; tuft of air tube sometimes very small.] 35 



34. Lateral hair of anal segment with three or four branches near base 



P. ciliata 



Lateral hair of anal segment single, or forked some distance from base ; 



teeth of pecten somewhat stouter than in P. ciliata P. hoivardii 



35. Antenna very large, inflated apically, two long bristles at outer third in 



addition to central hair tuft : air tube small with a paired tuft of very 



long hairs ; head hairs single P. discolor 



Antenna not inflated; air tube large, inflated, ventral tuft small or 

 obsolete 36 



36. Head hairs double or single 37 



Both upper and lower head hairs multiple P. columbiae 



37. Upper and lower head hairs double ; antennae unusually long and 



prominent 38 



Upper and. lower head hairs single 39 



3S. Pecten with three or four long spines, each with one to four teeth on one 

 side at base, sometimes with a small tooth on opposite side ; tuft of air 

 tube very small, placed laterally ; comb with seven or eight scales in 

 a curved row on a weak sclerotic plate, the upper scale smaller than 

 the rest ; single scale with a long apical spine and three to five much 

 smaller ones on each side P. ferox 



