236 Mosquitoes 



55. Central tooth of comb scales scarcely larger than 



the secondary, the scales usually more than 



twenty-five 56 



Central tooth of comb scales distinct, about 3 

 times as long as the secondary teeth, scales 

 less than twenty-five (Louisiana specimens). 

 (Fig. 53, page 250) OcJdcrotatus impiger. 



56. Ventral tufts of ninth segment generally ex- 



tending almost to cephalic margin of chitin, 



always at least half-way 57 



Ventral tufts of ninth segment not half-way 

 to cephalic margin of chitin. Antennae with 

 no small spinules, the tuft represented by a 

 single hair OcJdcrotatus varipalpus. 



57. Comb in two rows. (Louisiana specimens.) 



OcJdcrotatus " rep tans." 

 Comb in three or more irregular rows 58 



58. Spines of the tube, at least'those in the outer 



half of the row, with minute teeth above 



the largest tooth 60 



Spines of tube with no secondary teeth above 

 largest tooth 59 



59. Head tuft A, three-; B, three- or four-haired. 



Tube scarcely over three by one 



OcJdcrotatus cant at or. 



Head tuft A, three- ; B, five-haired. (Very rare.) 



OcJdcrotatus incouspicuus, 



60. Subdorsal tufts on abdominal segments three to 



six as long as two abdominal segments ; long 

 lateral abdominal tufts as long as three seg- 

 ments. Tracheae angled. Labial plate 

 twenty-one toothed. A, two-, B, three- 

 haired. Pecten continuous 



OcJdcrotatus JitcJni. 



