82 HOW TO COLLECT 



Ceratojjogon, are sufficiently distinct from Culicidce in outward form 

 to obviate any risk of confusion. In countries in which mosquitoes 

 abound they are recognized without difficulty. In England, how- 

 ever, where some twenty-hve species of the family occur, a large 

 amount of confusion apparently exists as to the characteristics of a 

 mosquito, or, as it is more commonly called, a gnat. This confusion 

 is mainly due to the fact that the midges iChironomidce), which, 

 with the exception of Cerato'pogon and one or two small exotic genera, 

 are peifectly harmless, often attract attention from the habit of the 

 males of dancing in the air in swarms on fine evenings, and, owing 

 to their similarity in shape, size, and general appearance, are 

 commonly mistaken for gnats {Culicklce). 



A fundamental structural difference between Culicidce and Chiro- 

 nomidw consists in the fact that in the former the costal vein 

 (fig. 2, c) runs right round the margin of the wing, while in the 

 latter (as in the vast majority of Diptera) it is confined to the front 

 margin alone, and stops short at the tip (compare plate, figs. 2 

 and 3). For practical purposes, however, more important differences 

 consist in the possession by the mosquito or gnat (except in Corethra 

 and Mochlonyx) of a greatly elongated proboscis (containing the 

 piercing-stilets, which enable it to obtain its food), whereas the 

 proboscis of the midge is so short as to be invisible without close 

 examination ; and also in the fact that while in Chironomidce the 

 wing is either bare or else uniformly clothed (membrane as well as 

 veins) with fine hairs, in Culicidce the veins are clothed vnth scales, 

 many of which project (especially towards the tip of the wing) at a 

 characteristic angle of about 45° (see plate, figs. 1, P). On the 

 costa {i.e. anterior margin of the wing) and the veins, the variously 

 formed scales differ materially in the different groups. The posterior 

 margin of the wing carries a deep fringe of elongated, feather- 

 shaped scales (see figs. 1, 1''). The body, legs, and palpi are also 

 clothed with hairs and scales ; in some species the antennae also may 

 be wholly or partially scaled. 



The preliminary stages (larva and pupa) of all mosquitoes are 

 passed in water, — generally stagnant fresh water, whether clean 

 or foul, and either in permanent ditches, ponds, or tanks, or in 

 temporary pools of rain-water; also in sluggish rivers and in salt water. 



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