406 ENTOMOLOGICAL news. [Nov., '08 



cell is sessile. Fig. 6 is from another specimen of the same 

 genus showing this cell broadly sessile. 



Figs. 7, 8 and g show the variations that occur in the length 

 of the petiole of this cell and also variations in the size and 

 shape of the discal cell in Tipula aequalis Doane. 



The position of the posterior cross-vein is a specific character 

 that is often used and is quite constant in some species. In 

 other closely related species it may be of no value on account 

 of the variations that occur. Fig. io shows the wing of 

 Dicranomyia badia O. S. with the posterior cross-vein in its 

 normal, that is, most usual, position, but it is often found much 

 anterior to this as shown in Fig. u. Figs. 12 and 13 show the 

 variations that may occur in the position of this vein in the 

 right and left wings of the same individual. (Limnobia trio- 

 cellata O. S.) 



In certain groups we often find extra or "supernumerary" 

 cross-veins that may or may not occur in all the individuals of 

 the species or they may be present in only one or in both of the 

 wings. Whenever they do occur their position is quite constant 

 for the species and sometimes for the genera. Fig. 14 shows, 

 such a vein occurring in the sub-marginal cell of both wings of 

 a specimen of Limnobia trio c elicit a O. S. 



A short stump of a vein often occurs near the origin of the 

 praefurca in some species. In Fig. 11 (Dicranomyia badia O. 

 S.) and Fig. 15 (D. Stigmata Doane) two such veins are 

 shown. 



Fig. 15 also shows a remarkable case of a distinct piece of 

 a vein occurring in a part of the wing where a vein never oc- 

 curs normally 



All or a part of a vein may sometimes be wanting in species 

 where it normally occurs. Fig. 10 shows two such veins in 

 the region of the discal cell. Only rarely do we see interpolated 

 cells as shown in Fig. 16 (Limnobia sciophila O. S.) and Fig. 

 17 (Tipula simplex Doane). Both of these aberrations occur 

 in the right wing only of these two specimens. 



These few examples selected from many that might have 

 been used show two things : first, the ever present tendency to 



