326 O. U. Osten Sacken: 



obliteratioii of the second vein) 'un facies coniplessivo dell' iiisetto 

 che lo distingua dalle altre Acrocere'. 



All that Mik says about Paracrocera is this: „The genus Acro- 

 cera contains species in which the second longitudinal vein is fully 

 developed (frei entwickelt) and the third is forked, and also such, 

 in which the second vein is wanting (or coalescent with the 

 first along its entire length) and the third is likewise forked. 

 The importance of this difference in its relation to the general struc- 

 ture (in genereller Beziehung) decides me to unite the species of the 

 second group, that is those, where the second vein is wanting, in a 

 separate generic type, which I call Paracrocera." Evidently Mik, 

 in attempting to write on this subject, was utterly unprepared for it. 

 He had no idea of the existence of a stunted State of the second 

 vein, and for this reason gare a superficial, and curiously erroneous 

 interpretation of its total disappearance. As I have shown, there is 

 no coalescence with the first vein, and these is no diffe- 

 rence of local structure pointing to a difference in the 

 general structure, and therefore no occasion for a new genus. 

 Now, that Mik's attention has been directed towards the species 

 with the stunted veins, in which of his two genera would he place 

 theniV Or would he establish new genera for each of thein, just as 

 he niade so many genera of Clmocera, that are superfluous even as 

 subgenera? 



A last Observation, to cap the climax. Meigen introduced the 

 genus Acrocera in „Illiger's Magazin" 1803, and quoted Si/rphus 

 glohidus Panzer, as type, or example. According to the rule of prio- 

 rity, the original generic name shonld be retained by this species, 

 which belongs to the group with the obliterated second vein, while 

 Mik calls Acrocera just the other group. And thus nothing is left 

 in defence of the rights of Paracrocera! 



My friend, Professor Mik, with his numerous „Referata" and 

 „Miscellen" has organised a System of regulär canalization, by nicans 

 of which, once a month, he irrigates the lields of Dipterology. Un- 

 fortunately, his good will notwithstanding, this irrigation carrics 

 many noxious niicrobes with it, which it will cost us ycars of work 

 and trouble to get rid of! 



Heidelberg, January 29, 1897. 



Postscript. It often happens that a monographer points 

 out natural subdivisions in a genus, and detines them, without Unding 

 it necessary to introduce new genera, or even subgeneric names for 

 them, Other entomologists have sonietimes interfered in such cases, 



