24 IXTRODUCTIOX. 



ends of the 4tli and 5th veins, approaching the Muscid type, yet 

 quite distinct from the true Muscid form as developed in Musca 

 itself and its allies. 



The CoxopiD^, PipunculidjE, PLAXYPEziDiE, Q^lsTRTD.5;, and 

 Phobid-i: have each one a striking and typical venation of its 

 own. Even in the vast mass of the MusciDjE, sensu lata, three 

 tolerably distinct types are present that contain the great majority 

 of the species ; these may be termed the Tachiuid, the Muscid, 

 and the Anthomyid respectively. The Acalyptrata, although 

 nominally of the same general plaii as the latter type in venation, 

 are as a rule easily distinguished by the small, equal-sized, or absent 

 wing-scales or tegulae, which in the Axthomtid.e are conspicuous 

 and of unequal size. 



Among the other families of Brachycera the student may at 

 first, from the wing alone, find it difficult to distinguish between, 

 say, tlie Tabanid^, Leptid.e, and Therevid,^ ; the various forms 

 of BoMBYLiiD.E and AsiLiD.E, with the allied smaller groups ; and 

 the somew-hafc erratic types met u ith in the Empii)."e ; but this 

 discounts but little the pronouncedly characteristic forms of the 

 other families, and a wider experience will enable him to determine 

 between these more allied types of venation. 



Eeverting to the Nematocera, the CECiDOxViYiD,i:,CHiROXOMiD.5;, 

 SiMULiiD.E, Blepharocerii),e, Dixid.e, and Tipulid.e at least 

 have quite characteristic venation. That of the Culicid-^: and 

 PsychomdjE is allied and, with the Khyphid^, may at first appear 

 to resemble the Tipulid.e, but a short study will enable the 

 student to differentiate them without much difficulty. The re- 

 maining families are not so distinctively characterised, and in 

 these closer examination is necessary. 



TeriittHolo'ji/ of venation. — As may be surmised, various systems 

 of venational terminology have been constructed, but, since this 

 is hardly the place wherein to enter into a discussion of their 

 respective merits and demerits, it will be only necessary here to 

 fully describe the system adopted in the present volume. Practi- 

 cally, it is a somewiiat modified form of JSchiner's terminology as 

 used in his ' Fauna Austriaea,' and as adopted by the principal 

 dipterologists up to the present day. 



Osten .Sacken, who, according to Schiner,* used a very old- 

 fashioned and unsatisfactory terminology employed oy Walker 

 and others of that period, entirely abandoned it in after years, 

 and the system accepted by him in his celebrated monograph of 

 the North American Tipulid.e (1869) was the basis of all his 

 subsequent work. 



Of other systems, mention may be made of that of Schummel, 

 mainly because he wrote extensively on Tipuliu.e, but he named 

 all the posterior cells backwards, that is, what is now called the 

 5th was his 1st, and he treated the two submarginal cells as 

 posterior cells, calling them the Oth and 7th. 



* Fauna Austriaea, ii, p. xxv. 



