Carpenter et al. : Mosquitoes of Southern U. S. 29 



taxonomic importance. For discussion it may be conveniently divided into 

 the mesonotum and the pleurae. 



The mesonotum includes most of the dorsal surface of the thorax and 

 consists of the scutum (combined praescutum and scutum), which makes 

 up the largest share of the mesonotum; the paratergite, a small region cut 

 off from the lateral margin of the scutum by a strong furrow just anterior 

 to and above the prealar area; the scutellum, a trilobed or rounded section 

 connected bumper-like to the posterior margin of the scutum; and the 

 postnotum, the convex structure between the scutellum and metanotum 

 (45,56). 



The pleural sclerites of the mesothorax occupy most of the side of the 

 entire thorax, with the exception of the small areas comprising the prothorax 

 and metathorax. The most important mesopleural divisions are the post 

 spiracular area, the region immediately behind the anterior spiracle; the sub- 

 spiracular area, below the anterior spiracle and adjacent to the posterior 

 pronotum and propleura; the sternopleura, a large, ham-shaped sclerite pos- 

 terior to the subspiracular area, projecting downward between the 1st and 

 2nd coxae and extending dorso-posteriorly nearly to the lateral margin of 

 the scutum; the pre-alar area, the neck-like upper portion of the sternopleura, 

 terminating in the pre-alar knob anterior to the wing base; the meseptmeron, 

 a large, well-defined, sub-rectangular sclerite adjacent to the posterior margin 

 of the sternopleura; and the meron, a small, triangular sclerite slightly above 

 and behind the 2nd coxa and immediately below the mesepimeron. 



The vestiture of the scutum (commonly referred to in most literature as 

 the mesonotum) is of considerable taxonomic importance in specific deter- 

 mination:,. The type of the scales and their coloration are characters com- 

 monly u«ed, and in some mosquitoes, Aedes aegypti, for example, there 

 can be little doubt as to the identity of the species once the definite bicolorous 

 scale pattern is seen. In many other mosquitoes, such as most Culex, scutal 

 scales are unicolorous, but their coarseness or fineness may be considered. 

 Setae, as well as scales, are generally present to some extent on the scutum; 

 and although not particularly uniformly distributed, considerable variation 

 in number occurring even within members of the same species, they lie in 

 fairly definite lines or areas (Fig. IOC). Those in the median longitudinal 

 row are known as the acrostichal bristles. The submedian longitudinal row on 

 each side of the acrostichals are dorso-central bristles. A supra-alar group on 

 the scutum above and in front of the wing base is generally prominent. The 

 anterior margin of the scutum, back of the head, may bear conspicuous setae, 

 but the prcscutellar space (mid-posterior area) has none. 



Th3 paratrraites are scaled in Aedes. but usually bare in other mos- 

 quitoes. The scutellum is definitely trilobed in all Culicines except Megarhinus, 

 in which it is rounded as in most of the Anophelines. Setae are borne on the 

 margins of the lobes of the scutellum, but are not as important in identifi- 

 cation as the scales which are generally present dorsally. The shape and 

 density of scutellar scales are often used in specific identifications of exotic 

 A edes. 



