XXIV INTRODUCTIOX. 



second by the fourth longitudinal in front, the anterior inter- 

 calary vein behind, and the posterior cross-vein at the oi;ter 

 side of the discal cell ; the third is bounded by the anterior 

 intercalary, and the fifth longitudinal vein and the posterior 

 cross-vein ; the fourth is bounded by the fifth longitudinal 

 vein in front and the posterior intercalary vein behind ; the 

 fifth by the posterior intercalary, the fifth longitudinal at the 

 outer end of the second basal cell, and the j^osterior basal cross- 

 vein at the outer end of the anal cell. The short vein which 

 separates the second basal cell from the discal cell is known 

 as the anterior basal cross-vein. Now, following the third 

 longitudinal vein outwardly it will be found to give off an an- 

 terior branch which runs forward to terminate in the anterior 

 border of the wing, or costa ; the cell included between this 

 fork and the vein itself behind is the second submarginal cell. 

 The second longitudinal vein borders the first submarginal 

 cell in front and terminates in the costa; between it and the 

 first longitudinal vein which has a similar course and termi- 

 nation is the viarginal cell ; between the first longitudinal 

 vein and the costa there is another parallel vein with nar- 

 row cells on each side of it, the vein is the ai(xiliary, and the 

 cell before it the costal, behind it the subcostal. Finally, near 

 the root of the wing there is a short cross-vein connecting the 

 auxiliary vein with the costa; it is known as the Itumeral 

 cross-vein. 



The student is urged to procure a copy of Comstock's Man- 

 ual of Insects for use in connection with this work. The 

 figures there given of the various parts of the external anato- 

 my of diptera and especially of the neuration, are the truest 

 to nature that I have ever seen. The nomenclature of the 

 wing-neuration there adopted, or some modification of it, is 

 destined to supplant the Meigenian or Scliinerian terminolo- 

 gies now almost exclusively used. I have not adopted it in 

 this work for two reasons: first, that it has not yet been fully 



