40 THE ENTOMOLOGIST. 



of veins and change in their direction, little difficulty arises 

 from such anomalies as an additional transverse vein, such as 

 subdivides the subapical areolet into two in Microdon, or the 

 pobrachial in Idioptera. The Hypocera are hardly to be 

 reduced with certainty to an analogous type, but the simpli- 

 city of the veining and the contrast between the strong veins 

 which end in the fore margin, and the faint ones (venulae) 

 which run to the hind margin, allow of and recommend 

 a different and simple nomenclature. 



" The Nemocera have a much greater variety in the veining 

 of the wings, and there is not a little difficulty in accommo- 

 dating to them the nomenclature used for the Brachycera, 

 partly from the multiplication of longitudinal veins, as in the 

 Psychodini, but yet more from the extreme faintness of the 

 veins in many, as in Simulia, and the ultimate disappearance 

 of all but one or two in the Cecidomyidse. Still, apart from 

 these extreme cases, we may observe such a degree of gradual 

 modification of the veining in most as to be able to apply an 

 analogous nomenclature to at least some of the principal 

 veins, and by relation to them to denominate the rest; 

 although it may be doubted whether it is not best to employ 

 a different and simpler numerical nomenclature when the 

 veins become few in number, and the closed areolets nearly 

 null or insignificant. Rhyphus has been taken as the type 

 by which to assimilate the nomenclature of the Nemocera to 

 the Brachycera, as it is scarcely possible to overlook the 

 analogy between Rhyphus and the Leptidae and allied families 

 of the Brachycera. From Rhyphus the transition is not 

 difficult to the Tipulidae, and thence to the Culicidae. From 

 the latter probably the Psychodini on the one hand, and the 

 Chironomidae on the other, may be illustrated with sufficient 

 probability. The transition from the Tipulidae to the Myce- 

 tophilidae is more abrupt; and these last, in respect to the 

 veining of the wings, not only undergo great diversities, but 

 present two manifest types separated by as abrupt an interval. 

 The first of these, characterized by the more or less complete 

 coalescence of the praebrachial and pobrachial areolets (Boli- 

 lophila, Thaumalea, Macrocera, Platyura, Ceroplatus, Dito- 

 myia, Asindulum, Diadocidia, Mycetobia), still preserves most 

 analogy to the preceding family. The second, in which these 

 two areolets are separated by a strong praebrachial vein, but 



