INTRODUCTION. 



According to the conclusions here adopted, the mosquitoes comprise a sub- 

 famil}^ of the order Diptera, and are divisible into two tribes. In our region, 

 covering the Xorth American continent from the southern edge of Canada to 

 the Isthmus of Panama, and including the Antilles and Trinidad, we treat in 

 this Avork 388 species, included in 25 genera : 8 genera with 85 species in the 

 tribe Sabethini and 17 genera with 297 species in the tribe Culicini. To this 

 should be added 7 species recently described but not included here, namely, 

 Wyeomyia rolonca, Wyeomyia intonca, Aedes thihauUi (Dyar & Knab, Proc. 

 Ent. Soc. Wash., xi, 173-174, 1910), Aedes ioliota (Dyar & Knab, Ins. Insc. 

 j\Ienstr., i, 77, 1913), Lesticocampa espini, Culex prasinopleurus and CiiJex 

 chalcocorystes (Martini, Ins. Insc. Menstr., ii, 65-76, 1914). Only a few parts 

 of our region have been at all adequately explored, many large areas not at all, 

 so that many more species doubtless await discovery. 



Fortunately, an unusually large proportion of the material before us consists 

 of bred specimens with larvse associated, so that we have been able to base our 

 conclusions upon comprehensive studies of the larvae as well as upon the adults. 

 The two of the present authors, Messrs. Dyar and Knab, who have made the 

 detailed studies for the taxonomic part of the present work, in fact began their 

 studies with the larv^ alone, thus arriving at an independent view. Further 

 research has abundantly justified these conclusions, although a more extensive 

 study has naturally led to some modifications in details. 



We have had prepared mounts of the male genitalia of a large majority of 

 the species and present herewith figures of them ; they enable us to draw gen- 

 eral conclusions from much more abundant material than has been before 

 gotten together. We find the characters of the male genitalia of the greatest 

 value and supporting the conclusions obtained with the larvae. 



Some confusion in systematic work has been brought about by the employ- 

 ment of certain terms and the worker must be cautioned against them as a 

 source of error in using the original descriptions. It has been repeatedly 

 pointed out by eminent dipterists that the structure commonly called metano- 

 tum belongs to the mesothorax; yet the error is being constantly perpetuated. 

 In our descriptions we call the part postnotum. The use of the term meta- 

 tarsus for the first tarsal joint is not only incorrect but has led to considerable 

 confusion. In such descriptions the second tarsal joint is called the first and 

 so on. In descriptions where neither a metatarsus nor a fifth joint is men- 

 tioned it is impossible to decide which joints are indicated. 



Concerning species previously described from our region, we have been able to 

 recognize a majority of them in the material before us. Some are still unrecog- 

 nized and probably unrecognizable, owing to the descriptions having been based 

 upon imperfect material. In a few cases we have adopted arbitrary designations 



V 



