I'i GNATS OK MOSQUITOES — tHAPTKH I 



Beneath the scutellum a part of the luetathorax is to be 

 seen called the metanotum, generally descending obliquely, 

 often very convex, and on each side a more or less inflated 

 space, called the lateral callosity of the metanotum. In 

 most mosquitoes this portion of the thorax is nude, but in 

 Mr. Theobald's new genera Wyeomyia and Trichoprosopon^ 

 is provided with certain characteristically arranged groups 

 of bristles ; and care should be taken not to confuse these 

 metathoracic tufts with somewhat similar but much more 

 uniformly present tufts on the scutellum, which overlie 

 them in the usual position of the parts. The poisers (Jial- 

 teres) have their origin beneath this callosity, and before 

 each is placed the stigma of the metathorax. In many 

 Diptera these are protected by membranous covers placed 

 above them, and called covering scales [teguloi s. squamcB). 



The abdomen is the third of the principal parts of the 

 body, but the word often is applied to the dorsal side only, 

 the under side being called the belly {venter). Its seg- 

 ments, as in other Orders, are counted from before back ; 

 but the anterior ones are often soldered together, while 

 the posterior ones are stunted and concealed. Much caution 

 therefore is desirable in counting them. The statements 

 as to their number are often rather arbitrary and conven- 

 tional, and must be taken to refer simply to such as are 

 plainly obvious under a simple lens. 



A careful observer will generally find they are really 

 more numerous ; and it must also not he assumed that the 

 entomologist's "segment" is necessarily equivalent to the 

 " somite " of the comparative anatomist. In many mos- 

 quitoes the scales clothing the abdonnnal segments are 

 so coloured as to produce a conspicuous alternation of 

 darker and lighter bands ; and the presence or absence 

 and relative position of these bands is of the greatest 

 importance in distinguishing the various species. 



This banding may be produced in three different ways. 

 Either the lighter coloured scales may be confined to the 

 front of the segment, in which case it is said to be " basally 

 lighter banded"; or they may be located on its hinder 

 portion, when the lighter banding is said to be " apical " ; 



