4 
in outward form to obviate any risk of confusion. In 
countries in which mosquitoes abound they are recognised 
without difficulty. In England, hoAvever, where some 
seventeen species of the family occur, though not, as a rule, 
in any great abundance, or causing much annoyance by their 
bites, a hu’ge 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 (Chironomidae), which, with the exception of the 
genus Ceratopogon are perfectly harmless, often attract 
attention from the habit of the males of dancing in the air 
in swarms on tine evenings in spring and early summer, 
and, owing to their similarity in shape, size, and general 
appearance, are commonly mistaken for gnats fCulicidae). 
A fundameirtal structural difference between Culicidae 
and Chii’onomidae consists in the fact that in the former 
the costal vein 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, how- 
ever, more important differences consist in the possession by 
the mosquito or gnat of a greatly elongated proboscis (con- 
taining 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 Chironomidae the v/ing is either bare or else 
uniformly clothed (membrane as well as veins) with tine 
hairs, in Gulicidw, while the membrane of the wing is bare, 
the veins are clothed with flattened' hairs or scales, which 
project (especially towards the tip of the wing) at a character- 
istic angle of about 45° {see plate. Figs. 1, 1"). On the costa 
(i.e., anterior margin of the wing) and certain of the veins, 
especially the mediastinal and 1st and 5th longitudinal (for 
the nomenclature of the veins compare Figs. 1 and 2), the 
hairs are replaced either wholly or in part by truncated 
scales ; but hairs and scales are merely modifications of the 
same structures, aiul in some species the scale-like form may 
