334 CHARLES T. BRUES. 



the costal vein. Below this is the first longitudinal, which re- 

 mains separated from the costa until near its tip, where it curves 

 upward and meets the costal vein ; near the base of the wing it is 

 connected with the costa by the short humeral cross-vein. Just 

 beyond it and anterior to the first vein is the mediastinal or auxiliary 

 vein, which is often obscure or completely absent in some forms. 

 The third vein is usually quite stout, and meets the costa at its 

 apex. The second vein is short (absent in many forms), and is 

 an anterior branch of the third. It usually meets the costa near 

 the tip of the latter. The costa is bristly except in a very few 

 cases, as is also the root of the wing behind. The four discal 

 veins are usually considered as the fourth to seventh longitudi 

 nal veins, and are always more delicate than the basal veins ; 

 occasionally the last (seventh) may be absent. As a rule, the wings 

 are hyaline or but slightly colored, but in some few European species 

 the anterior border is strongly infuscated. Peculiar wing pores have 

 been described, which are upon the apical portion of the third vein.* 



These pores are very numerous in Phora pachyneura Lw., in which 

 case they extend over the apical three fourths of the third vein. The 

 females of many genera have more or less vestigial wings. In 

 such cases the venation is obscured or obliterated, and the wings 

 often assume grotesque forms or are ornamented with enormous 

 bristles {e.g., Acontidoptera and Xanionotuin) ; in another group 01 

 genera the females are completely, destitute of wings. Even the 

 halteres are wanting in some wingless females. 



The abdomen is of the usual form, generally more or less conical 

 in the female, and often with a conspicuous hypopygium in the 

 male. The ovipositor of the female is generally soft and delicate, 



* The following remarks upon the wing pores are from Felt, 10th N. Y. Kept. 

 "An additional character which may prove to be of specific value is found in the 

 number and location of certain ' pores ' or pore-like structures. The pores, four 

 in number (i. e., in Aphiochieta albidohalteris), occur in a slightly curved row along 

 the middle on the outer side of the second heavy vein, where it anastomoses with 

 the costal vein ; a short stump extends beyond the anastomosis and inclines a 

 little away from the costa. 



''The pores are less than half their diameter apart, the last one being close to 

 the apex of the stump. Each consists of a depression, surrounded by a raised 

 circular ring of chitin. These pores must not be confounded with the scars on 

 the costal vein when a bristle is removed ; they appear to have no connection 

 with either bristles or setae." 



