THE CANADIAN ENTOMOLOGIST. 1^17 



margins of the mediana and of the sinus. There are sometimes between 

 mediana and costa in the apical part of the wing four or more not well 

 defined transversals, and between the mediana and submediana four or 

 less well defined transversals ; as far as I am able to see, all these trans- 

 versals are only connected with the sinus and not with the mediana itself. 

 The submediana (fourth vein, or forked fourth vein, Westw., McLachl.) 

 enters the wing from below as a strong vein, and sends from beyond the base, 

 before the end of the basal fourth of the wing, a much stronger vein, the 

 post-costa, obliquely to the hind margin. The submediana runs parallel 

 to the mediana as far off as these veins from the costa. The submediana 

 runs straight to the tip of the wing ; the part of this vein which is called 

 by McLachlan the upper branch of the sector, is in fact the submediana 

 itself. This is proved by 0. Wesiwoodi, where the part considered as 

 fourth sector is obliterated, and the part considered as upper branch is 

 well developed. The abnormal specimen of O. i-iificapilla shows the 

 same arrangement. After all, as far as I know, when veins are partly or 

 totally aborted, the branches are first to disappear, and are followed by the 

 main stem. Therefore we have to call the vein which is again furcated after 

 the middle of the wing the lower branch of the submediana. The space 

 between the mediana and the submediana, closed by a curve before the 

 apex of the wing, is properly called the elongated cell or discoidal cell, and' 

 is only wanting in O. Weshvoodi. There are some, but always few (3 to 

 5) transversals in the cell. The lower branch may be bifurcated again 

 (Embia, Olyntha), and in abnormal cases the branch also bifurcated, 

 at least in one wing. In the spaces between these branches and 

 below them are a few scattered transversals without much regularity. 

 Near the base the submediana is connected with the mediana by a very 

 short transversal (between 4^ and c in fig. 2, Wood-Mason, 1. c.) in the 

 hind wings about opposite the origin of the post-costa, in the front wings 

 a little later. This short transversal vein, examined with the microscope? 

 is found to be combined of two branches, one originating from the 

 mediana, and another from the submediana. The first one crosses the 

 last one, and a series of hairs following it shows an undeveloped vein 

 (the rudimentary first branch, fig. 3, c, Wood-Mason, 1. c.) This connec- 

 tion is homologous to the arculus of the Odonata, or the cross on the base 

 of the front wings of Palpares, etc. Such a connection is often found 

 present, when the wing is to be stiffened for a more powerful flight, or 

 to give to a delicate wing more stability. This connection is not always 



