1922] Forbes: Wing-Venation of, Coleoptera 333 



M4 because they are the, extreme members of the complex group shown 

 by Hydrous. They might be considered M1+2 and M3+4 if the extra veins 

 of Hydrous be considered secondary. 



In almost all forms (except a few Adephaga and Cupes) the base 

 of media fades out, leaving the main part of it attached at the apex 

 only. This sector of the vein is known as the medial recurrent (Mr). 



Cubitus. — There is never but one vein supplied by the cubital 

 trachea (leaving out of account the vein here treated- as 1st A). Many 

 Neuroptera also. have .only, a single corresponding cubital, or a. -single 

 main vein supplemented by some secondaries. To judge by the arrange- 

 ment of these terminal branches the missing cubital branch has either 

 fused completely with the surviving one, or has atrophied on the 

 posterior side of it. At this point some LamelHcorns have a trachea not 

 represented by any very distinct vein in the imago, which may possibly 

 be the missing Cu2, but is more hkely a last trace of 1st A. 



In the Hydrophilidse and Haliplidse (Figs. 19 to 23), Cu runs toward 

 the margin as an independent vein. Comparison with these two fam- 

 ilies shows that in the remaining Adephaga the apex of Cu has disap- 

 peared by atrophy, while the double trachea suggests that in the 

 Polyphaga it has fused with M4. 



First anal.— This is simple. With the atrophy of its base the cross- 

 vein cu-a remains to connect it with the stem of cubitus (Hylecoetus, 

 Fig. 40). In some forms, as in the Lampyridae (Fig. 32) it is not clear 

 whether it is the base of the main vein or the cross- vein, which has 

 disappeared. 



Second anal— The second anal trachea divides, at the maximum, 

 into three branches. The first corresponding vein has been universally 

 considered a branch of the vein here designated 1st A, but if that is the 

 case the extraordinary course of its trachea, which actually has to 

 turn basad in some Buprestidce, to enter its cavity, and which may run 

 for some distance in a common vein-cavity with the first anal trachea 

 without fusing with it, remains entirely unexplained. This first branch 

 is doubtless the one that has disappeared in the Tenebrionidse^ and 

 Adephaga (where there is no corresponding trachea) ; but in the higher 

 Phytophaga it seems rather to be 1st A that has vanished, as there is 

 no trace of a first anal trachea arising from Cu. The second branch of 

 2d A has nothing extraordinary, and receives the unbranched second 

 anal trachea in the Tenebrionid^e (in some specimens only of which 

 the third branch also receives a tracheal twig). The third branch has 

 apparently evolved in two distinct ways. In a few forms it is entirely 

 independent (as in Attagenus, Fig. 35, and many Buprestidse, Fig. 34). 

 The next, and perhaps most primitive condition, is for it to be con- 

 nected by a cross-vein to the upper fork of 3d A, as plainly shown in 

 Cehrio (Fig. 30). It is my belief that the same condition holds in the 

 other Elateridce (s. 1.) and Lampyridae, where there are three anal 

 twigs below the second anal furrow, and the vein bounding the wedge- 

 cell is transverse and tends to disappear by atrophy (Alaus, Pyrophorus, 

 Calopteron). In most forms, however, the apex of this branch has 



