2 MOSQUITOES OF NOETH AMERICA 



of the abdominal segments of Dixa. In some of the Corethrinffi the respiratory 

 system is represented by two pairs of air-bladders or " floats." The shape of 

 the thorax, being composed of 3 segments closely consolidated, is a good diag- 

 nostic character, except in the Dixinaj. Imms says (Parasitology, i, 122, 1908) : 

 In the Chironomidse " the first three post-cephalic segments become greatly 

 swollen towards the end of larval life, in consequence of the developing imag- 

 inal organs contained within them. However, there is no fusion into a compact 

 thorax, though the limits between the second and third segments may become 

 partially obliterated." The presence of long setse, particularly laterally on the 

 thorax and abdomen, is also characteristic and fails only in a few Corethrinse. 



The separation of the Culicidae into its subfamilies on larval characters de- 

 pends upon the presence of the mouth-brushes in the Culicinag and Dixinge, 

 which are not developed in the Corethrinae, besides which in general appearance 

 the larvae are quite unlike, and an experienced collector will never mistake 

 them. The Corethrinae are a small group, but possess remarkable diversity of 

 form. All the species known are predaceous, usually upon the larvae of the true 

 mosquitoes. In general, all the larvae that seize their prey with the antennge 

 instead of the mandibles or maxillas belong to the Corethrinte. This character is 

 least developed in the genus Eucorethra {Pelorempis), but its position may 

 be recognized by the absence of the mouth-brushes. This form, Eucorethra 

 underwoodi Underwood, leaving aside its predaceous habit, is near to the gener- 

 alized ancestor of the Culicinae, and it is interesting to note its general resem- 

 blance to the culicine genus Anopheles, which we here place the lowest of the 

 true Culicinae. The larvae of the Dixinas are easily distinguished by having the 

 three thoracic segments not widened and unconsolidated. 



The subfamily Culicinae. or true mosquitoes, are the subject of the present 

 work. They may be divided into two tribes, as follows : 



- Table of Tribes of the Subfamily Culicin.e 



1. Occiput with a pair of coarse bristles, well differentiated from the setae along 

 ocular margins, projecting forward at the vertex; mesonotum without 

 setae on the disk, clothed with scales only except around the margin; post- 



notum with a group of small setae posteriorly Sabethixi (p. 19) 



Bristles on the vertex present or absent, rarely in a single well differentiated 

 pair; mesonotum usually with two rows of coarse setae longitudinally 

 across the disk; postnotum usually without setae, a few forms with from 

 one to three bristles present Culicixi (p. 189) 



These tribes are also well characterized as larvae and pupae : 



Table of Tribes of the Lakv^ of Culicix.e. 



1. Anal segment without ventral brush, the hair tufts all paired Sabethini 



Anal segment with unpaired ventral median brush Culicini 



Table of Tribes of the Pup.e of Culicinae. 



1. Abdominal segments 7 and 8 with ample hair tufts at angles; paddles small 



Sabethini 

 Abdominal segments 7 and 8 with hairs or small tufts; paddles large and broad 



Culicini 



