262 GNATS OR MOSQUITOES — CHAPTER X 



lu endeavouring, then, to make out the sub-family to 

 which any specimen under examination should be referred, 

 the points to be first noted are : — 



(1) The structure of the proboscis, whether formed for 

 piercing or otherwise, and whether strongly curved or quite 

 or nearly straight. 



(2) The relative length of the palpi in both sexes and its 

 form, where specimens of one sex only are available. This 

 being determined, species may be referred to their genera in 

 many cases by noting the following points : — 



(a) The character of the clypeus, whether nude or 

 armed with bristles or scales. 



(6) The form and arrangement of the scales on the vertex 

 and nape, and also on the scutellum. 



(c) The character of the metanotum, whether nude or 

 provided with bristles, or with bristles and scales. 



[d) The relative length of the second antennal joint. 



It is a labour-saving plan to in each case note down 

 these points in pencil before proceeding to the more detailed 

 examination of other characters. 



In each genus the series of descriptions will be found to 

 be preceded by a table, intended to serve as a key to the 

 ready identification of the species belonging to it ; and the 

 species will be found to be arranged in the same order as 

 they fall in the table. 



The plan of these tables is based on that adopted by 

 Ficalbi for the European species, but has been somewhat 

 modified owing to the much larger number of species that 

 have to be accounted for. 



It must be, however, distinctly understood that tables of 

 this sort can only be employed as a sort of convenient index 

 to facihtate the ready identification of species, and neither 

 are nor pretend to be, in any sense, a natural classification. 

 At the same time, as a matter of fact, although occasionally 

 species will be found to be inconveniently separated from 

 their nearest allies, the plan adopted generally places closely 

 allied species in fairly consecutive order. 



The general principle of the tables is to place first the 

 most elaborately adorned species, and to relegate those that 



