H. C. EFFLATOUN. 



R5 celJ (R5) or first posterior cell : between the same veins, 

 from the radio-median cross-vein to the outer margin of the wing; 

 this cell may be widened at the end or mav hâve parallel sides but 

 very rarely narrowed at the end. 



Media cell (M), or second basai cell : between Ml and M3 + Cul. 

 from the bifurcation of thèse veins to M3 cross-vein; more or less 

 broad or widened at the end and sometimes very much dilated. 



Ist Media 2 cell (Ist M2), discoidal or discal cell : between the 

 same veins, from M3 to the médian cross-veins; more or less long 

 and more or less widened at the end, but very rarely narrowed at 

 the end. 



2nd Media 2 cell (2nd M2), or second posterior cell : in con- 

 tinuation of the preceding cell, between the same veins, from the 

 médian cross-vein to the outer margin of the wing: more or less 

 widened. 



Cubitus cell (Cu), anal or third basai cell : below M cell, 

 between M3 + Cul and Cu2-f-A2 from their bifurcation to Cul -t- 

 Cu2 cross-vein ; this cell is very important with regard to the shape 

 of its inferior angle which is rarely obtuse, usually being drawn out 

 into a point which is narrow or broad ; it mav be shorter than M cell 

 or of eqiial length or longer and is sometimes much prolonged, 

 reaching almost to the hind margin of the wing. 



Cubitus 1 cell (Cul) or second posterior cell : in continuation 

 of the preceding, between M3 + Cul and Cia2-t-A2 from Cul + Cu2 

 cross-vein to the lower margin of the wing; less important. 



2nd Anal + Srd Anal cells (2ndA hSrdA) or third posterior + 

 Axillary cells : between Cu2 + A2 and the lower margin. at the 

 base; thèse two cells are partlv fused with the axillary lobe aiid the 

 preceding cell. 



The pattern of the wings is very variable and is of great imi^nr- 

 tance in the distinction of the species and even of the gênera; how- 

 ever in this last case caution is necessary. In the palaearctic species 

 the patterns may be classified in two distinct aiid principal types, 

 the banded type and the reticulate type; the two types however 

 may rarely be found in the same w^ing in exotic species, such as in 

 Acrotaenia (Bezzi). The colouring of the wing is due to a tint in 

 the wing-membrane itself, but if tlic wing of Schistopterum be 

 examined microscopically it will be found due to peculiarly shaped 

 and coloured hairs on the surface. 



The ground colour of the wings may be considered as hyaliiic 

 in the banded tvpe, which is well developed in the so-called "rivu- 

 lets" of many Trypaneids; the species which possess black wings 

 with hyaline indentations and spots {Spheniscomyia etc.) are in 

 reality an exaggeration of this type. There are other species which 

 hâve almost entirely black wings but with the hyaline spots less 



