60 MOSQUITOES OF NORTH AMERICA 



and form a kind of projecting collar under which the head is inserted. The 

 prothoracic lobes bear coarse bristles which are usually irregularly scattered over 

 the surface; where the lobes are collar-like, as in Sabeihes, the bristles are in- 

 serted along the anterior edge. 



The scutellum is usually sinuate in outline posteriorly ; there is a large median 

 lobe and a smaller lobe on each side. Each lobe bears a group of coarse setae. 

 Theobald has described a curious mosquito (Rachionotomyia ceylonensis) from 

 Ceylon which is characterized by the " scutellum drawn out into a large, thick, 

 backwardly projecting spine, hiding to a large extent the metanotum." In 

 Anopheles and a few other forms the scutellum is feebly arcuate behind without 

 indication of lobes; there are, however, forms with feebly differentiated lobes 

 which form the transition to the distinctly trilobate ones. 



The region of the mesotergum lying in front of the scutellum is called meso- 

 notum in descriptive work and for convenience we have retained this term. It 

 offers no modifications in structure of a tangible character. It bears coarse setae, 

 variously disposed, and their arrangement and abundance are of some signifi- 

 cance. There are always coarse setge along the anterior and lateral margins and 

 these are particularly coarse and abundant over the roots of the wings. In the 

 Sabethini, and also in Megarhinus, the disk is devoid of setae. In most of the 

 Culicini there are numerous bristles upon the disk arranged more or less in longi- 

 tudinal series. There is a double series along the median line which does not, 

 however, reach the posterior margin. Two other rows of setae form sublateral 

 longitudinal series. 



The part of the mesotergum behind the scutellum is called metanotum in most 

 descriptive work. This term implies that the structure belongs to the metathorax 

 whereas in reality it is mesothoracic. We have, therefore, in the systematic part 

 of the present work, adopted the term postnotum. The postnotum shows no 

 variations in structure of a tangible sort. Usually it is nude and smooth or 

 pruinose. It may be indistinctly keeled. In the Sabethini there is a group of 

 setae, medianly near the posterior margin. In the genus Dinomimetes of the 

 Culicini one or two coarse, spine-like bristles are present in the same situation ; 

 these arise from a common base, while in the Sabethini the setae are inserted 

 separately. 



THE WINGS. 



The wings are long and narrow. The venation is the same throughout the 

 family Culicidas and shows only variation in minor details. In the nomenclature 

 of the veins we follow Williston. The costal vein encompasses the wing and is 

 strongest along the anterior margin. The auxiliary vein encloses a narrow area, 

 the costal cell, along the anterior margin and terminates in the costa about two- 

 thirds the length of the wing from the base. Following this are six principal 

 veins of which the second, fourth and fifth are forked. The first vein is sepa- 

 rated from the auxiliary vein and the costa by a narrow cell, the subcostal cell, 

 and joins the margin near the apex of the wing. The second vein originates 

 from the first vein behind the middle of the wing. The third vein springs from 

 the second beyond the middle of the wing and is angulate at its base ; the small 



