NORTH AMERICAN DIPTRRA. 



it is alone present and the pulvilli are wanting (see 

 Bibionidse, fig. ya). 



Fig. ii. Male genitalia. i, Tipulidae (Diotrepha}\ 2 Tipulidae 

 (Atarba]\ 3, Tipulidae (indet.); 4, Culicidse (Aedes]\ 5, Dolichopodi- 

 dae (Dolicho/>i(s}\ 6, Asilirlse (^ 



ABDOMEN. 



The abdomen is composed of a variable number of seg- 

 ments, more or less closely fused together. The normal 

 number for insects, nine, are rarely all visible (the Tip- 

 ulidse are examples). They are counted from the base 

 on the upper side. In not a few cases the first two are 

 so closely fused together, and the first one abbreviated, 

 that the nomenclature leaves some doubt in the mind of 

 the student. The upper part of the abdomen may be es- 

 pecially indicated by the word dorsuni, but in general, the 



