AMALons. 2G3 



0. S., and in the European species A. liUoralis M., schincri Egg., 

 occulta M. The structure of the posterior fork of the fourth 

 vein undergoes some modifications which deserve lilvcwise to be 

 mentioned. In most of tlie species (au?-ipenm's, hyperborea, cal- 

 car, inconstans, and the European littoralis M., tipidina Egger, 

 schiyieri Kolen., unicolor Schum., immaculata Sclium.) this fork 

 is petiolate, or in other words, tlie inner end of the fourtli posterior 

 cell (enclosed by this fork) is more remote from the basis of the 

 wing than the inner end of the discal cell, or when it is open, of 

 the third posterior cell. In A. vernalis, however, as well as in 

 the European A. occulta M., gmundensis Egger, and opaca 

 Egger, the posterior fork of the fourth vein is sessile, that is, the 

 origin of the branch forming it is coincident with the first branch- 

 ing of the fourth vein ; hence, the inner end of the fourth posterior 

 cell is equidistant from the basis of the wing with the inner end 

 of the discal cell, or, when it is open, of the third posterior cell. 

 The discal cell is closed in the normal specimens of A. calcar, 

 vernalis, and inconstans ; it is likewise closed in the tvv^o remain- 

 ing North American species, A. auripennis and A. hypei'horea, 

 of which, however, I have only single specimens before me ; also 

 in the European A. tipulina Egger. In the European A. littor- 

 alis M., schineri Kol., and unicolor Schum., the discal cell seems 

 to be variable, sometimes closed, often open. In A. occulta M., 

 immaculata Sch., gmundensis and opaca Egger, it is open (at 

 least in normal specimens).* The shape of the discal cell is usu- 

 ally pentagonal ; but in A. vernalis, owing to the above-mentioned 

 structure of the posterior fork of the fourth vein, it is elongated 

 and narrow. When the discal cell is closed, the second posterior 

 cell is usually petiolate ; in A. vernalis it is sessile ; in most 

 specimens of A. incoiistatis it is sessile or subsessile. The small 

 cross-vein is generally in one line with the inner end of the discal 

 cell (or of the third posterior cell, when the discal is open), and 

 often with the great cross-vein ; this relation is somewhat variable 

 in A. inconstans. The fifth longitudinal vein is somewhat arcuated 

 towards the end ; the sixth and seventh are straight, or almost so. 

 In A. hyperhorea the second basal cell is divided in two by a 

 supernumerary cross-vein ; the same is the case with the Euro- 



' The data about the European species are takeu from Dr. Schiner's work. 



