HOW TO COLLECT MOSQUITOES (cULICIB^j). 81 
The other blood-sucking Diptera, with the possible exception of 
Ceratojiogon, 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-five 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 (Chironomidce), which, 
with the exception of the genus Cercttopogon, are perfectly 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 (Culicidce). 
A fundamental structural difference between Cidicidce and Chiro- 
nomidte 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, fi°-s. 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 Cidicidce the veins are clothed with sccdes, 
many of which project (especially towards the tip of the w r ing) at a 
characteristic angle of about 45° (see plate, figs. 1, l a ). 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, l b ). The body, legs, and palpi are also 
clothed with hairs and scales ; in some species the an tenure 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 
G 
