MOSQUITOES, THEIR DEFINITION AND POSITION 

 IN THE CLASSIFICATION OF INSECTS. 



Mosquitoes are small two-winged flies belonging to the order Diptera. For a 

 general view of this order the student is referred to Prof. S. W. Williston's 

 Manual of North American Diptera, of which the third edition was published 

 in 1908. The following paragraphs, extracted from this work, define the family 

 Culicidse, and separate it from all other flies : 



Flies of a softer texture, not ectoparasites upon warm-blooded animals. 



Mesonotum never with a complete V-shaped suture, rarely with any distinct suture. 

 For the most part small flies. 



No ocelli. 



Antennae not composed of three joints and an arista or terminal style .... 



Wings with more than a few longitudinal veins and with apparent cross-veins .... 



No discal cell. 



The marginal vein encompasses the wing; second and fourth longitudinal veins 

 furcate; many veined. 



Anterior cross-vein near middle of wing, distinct; second basal cell large and dis- 

 tinct; wings not folded roof -like when at rest. 



Wings tomentose; fringed on the hind margin; antennas of male usually bushy 

 plumose; the second and third veins separate at an acute angle. For the 

 most part blood-sucking flies; mosquitoes CtrLiciD.s; 



The wing venation of the Culieidae is remarkably homogeneous throughout 

 the family. It consists of a well-developed auxiliary or mediastinal vein, six 

 longitudinal veins, of which the second, fourth and fifth are furcate, and 

 humeral anterior and basal cross-veins. The details of structure and their 

 modifications will be found discussed in the chapter on the anatomy of mos- 

 quitoes in the first volume of this work. 



The Culicidse, according to Williston, are divided into two subfamilies, sepa- 

 rated as follows : 



Proboscis short, not adapted for piercing CoRETHEiN.a: 



Proboscis much longer than the head, firm, adapted for piercing Culicin^ 



The genus Dixa, which Williston and others treat as a distinct family, under 

 the name Dixidse, should, in our opinion, be considered as a third subfamily of 

 the Culicidse, the Dixinse. 



The larvffi of the Culicidse are characterized by the presence of a complete, well- 

 ehitinized and completely exposed head with well-developed mouth-parts. In 

 nearly all the forms the respiratory system is well-developed and there are two 

 main tracheal trunks extending from the anterior part of the thorax to the eighth 

 abdominal segment. Here the system opens outwardly, either through two spir- 

 acles directly upon the dorsum, or, more frequently, through a chitinous tube. 

 The larvse are therefore metapneustic, all the other spiracles being closed. In 

 further adaptation to the aquatic life the tracheal openings are protected by a 

 variously developed closing mechanism. Pseudopods are absent, except on some 



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