WINGS. 



37 



venter or under part is alone thus contradistinguished, 

 The male genitalia, which in many cases are of compli- 

 cated structure, and of much value in classification, are 

 known collectively as the hypopygium, and this term is 

 usually restricted to the male genitalia, though some- 

 times used also for the female organs. The ovipositor of 

 the female abdomen very frequently projects from the 

 abdomen, and is sometimes extremely long; its structure 

 may be characteristic of genera or families. The more 

 detailed description of the parts of both these organs it 

 is unnecessary to go into here; they may be studied in 

 the different families, where they often find useful appli- 

 cation in the separation of species, though rarely of 



genera. 



Fi^. 12. Win^r of Tabanus. 



WINGS. 

 To understand the venation or neuration of the wings 

 the student may select a common large horsefly ( T-aban- 

 idse). Observe near the middle of the wing directed 

 transversely, a large, oblong, five or six sided cell, sur- 

 rounded on all sides by other cells. This is the discal 

 cell and is present in nearly all flies. Somewhere on the 

 vein (fourth longitudinal), that bounds this cell in front, 

 will be seen a short connecting vein, directed anteriorly, 



