324 €. H. Osten Sacken: 



tlio marginal, and that citlior conipletely coalcscent wlien tlic 

 seconrl vein is cntirel}' snpprcsscd, or inco nipletely, wlicn it is 

 only stnnted. Erichson has alroady noticed tliis pccnliarity wlion. 

 in bis charactorzation oi Acroccra, he said: 'Die Flügel haben in eist 

 zwei TTnterrandzellen'. On p. 167, be says about A. sanguinca Meig., 

 Mass dem vorderen Ast der Gabelader ein paralleler Ast vorhergeht, 

 wodurch drei Unterrandzellen gebildet werden.' In onr terniinolngy 

 tbis means the presence of a distinct second vein, and of two 

 submarginal cells. As Erichson did not possess specimens of .<?(,-??,- 

 guhica at that time, it is evident that be derived bis Information 

 from Meigen's figures (the cxcellent onc in Classific. Tab. S. f. !>;') 

 — 2(), and the same, on a snialler scale, in tho Syst. Beschr. III, 

 Tab. 24, f. 1).') M eigen in bis Ictterpress (Syst. Beschr. III, p. 1».")), 

 describcs another species, A. nigrofemorata, and says that 'the ve- 

 nation is somewbat diffcrent from that of stinguinea,'' and refers to 

 flg. 10. The dift'ercnce, as the ligui-e shows. consists in the stnn- 

 ting of the second vein, wliich is interrupted half-way bcfoi'o reaching 

 the margin. Erichson (p. 1G7) dcsci-ibcs tbis same character, wben 

 he says about nigrofcmorata-. 'die Flügel haben wieder die einfache 

 Gabel'. Erichson and Gerstaecker judged of the species mcrely 

 from Meigen's data, and I am not aware whetber any specimens 

 of nigrofemorata have bocn discovered since Meigen's time. In 

 fact. Schiner (Fauna I, p. 73 and in the Syst. Catal.) takes nigro- 

 fcmornta for a synonym of sanguinea. For tbis reason, wo cannot 

 be snre wbethcr the stunting of the second vein in mgrofetnorafa 

 is a permanent character, or a mere casual or individual aberration.-) 

 We have another instance still of the instability of the structure 

 of the second vein in the genus Aerocera. About A. Inmacidota 

 from Washington, D. C, Loew (Cent. VI, 33) says: 'vena longitudi- 

 nalis secunda praeter apicis rudimentum omnino deest; vena longi- 

 tudinalis tertia furcata et transversae ambae perfectae, ut in spe- 

 ciebns plerisque'. Tbns we have in sanguinea a complete second 

 vein;-') in nigrofrmorata an incomplete one at one end; in bima- 

 calata an incomplete one at the other end; and in other species 



^) Meigen, in bis Vol. III, p. 94, at boltom, by a slip of the 

 pen has fig. 10, iiistead of fig. 9 in tlie diagnosis of sanguinea. 



-) Schiner (Fauna I, p. 72) likewise doscribes fhe venation of tiio 

 genus Aerocera as 'very variable and irregulär; the third vein has 

 generally a distinct fork, and there are two, often incomplete, sub- 

 inarginal cells'. 



■') Also in irigramma Loew, Stelviana Pok., trigrammoidcs Pok. 



