596 DIPTERA OF AUSTRALIA, 



is also committed in my paper on the Bibionidte (I.e., pp. 1363- 

 1386, pi. 39). The blunder arose from the fact that the second 

 longitudinal vein is wanting in the wings of the Mycetophilidse 

 and Bibionidse, whereas it was considered to be present by me. 

 What is apparently the second longitudinal vein is in reality the 

 homologue of the third longitudinal vein in other families. Con- 

 sequently all the succeeding veins and cells in the wings likewise 

 received incorrect names. 



Baron Osten-Sacken has favoured me with the following notes 

 on the terminology of the venation : — 



" It is a sore subject in Dipterology ; it is not worked up yet as 

 it ought to be. Schiner, in one of his papers, reproached Loew for 

 having worked twenty-five years on Diptera without settling the 

 terminology of the venation. Loew did it for the fii'st time in 

 Mon. N. Amer, Dipt., I., (1862), when he was called upon to 

 write a general introduction to Dipterology. This essay is obscure 

 and unsatisfactory. On p. xvii. for example ("In most Diptera," 

 etc.), Loew should have quoted instances of the structures he 

 describes. On p. xxiv. he should have repeated in figs. 2 and 3 

 the lettering of fig. 1, in order to show the correspondence of the 

 veins and cells in the three diSerent wings. Why did he not do 

 it 1 The answer will result I think of what follows : 



" It was Schiner, a couple of years later (Verh. Zool Bot. Ges. 

 Wien, XIV., p. 193-211, 1864), who laid the foundation of a 

 theory of the venation. He showed that Orthorhapha and Cyclo- 

 rhapha have their respective venations built on a difierent plan. 

 In the Orthorhapha the discal cell is formed by the forking of the 

 fourth vein (Schiner's Discoidal-ader) ; in the Cyclorhapha the 

 fourth vein does not fork ; the so-called discal cell is formed by 

 the fourth and fifth vein (Postical-ader of Schiner) ; compare 1. c, 

 p. 207, " Betrachtet Man die Eigenthiimlichkeit," etc. In other 

 words, the discal cell of the Orthorhapha is not homologous with 

 the so-called discal cell of the Cyclorhapha ; and the so-called pos- 

 terior transverse vein of the Orthorhapha is not homologous with 

 the posterior transverse vein of the Cyclorhapha. Loew did not 



