1922] Forbes: Wing-Venation of Coleoptera 329 



In the present paper I shall try to identify the main veins 

 of the Coleopterous wing with those recognized in other orders, 

 and will suggest a tentative scheme of their branching. The 

 main identifications, though differing from the several schemes 

 which now hold the field, are supported by a convergence of 

 evidence from the tracheation and basal sclerites, as well as by 

 the character of the veins themselves. 



In interpreting the tracheation my first assumption has been 

 that each trachea which is separate in the most generalized 

 form available, represents a single main vein, and that together 

 all the veins are accounted for. In a single particular this 

 assumption has been slightly modified — the identification of 

 the first anal stem, as discussed below. 



To take up the main veins in order: 



Costa. — In all the orders of insects the costal vein lies along the 

 costal edge of the wing, or is preceded only by a membranous strip, 

 and runs far basad, forming a hook-like articulation with the body. 

 It contains a weak trachea or none. In the Coleoptera studied the 

 base of the costal edge is occupied by a vein, which in Calosoma contains 

 a weak trachea. This is certainly costa. In a few forms (Silpha, 

 Fig. 24, and Buprestid^, for instance) there is a little membrane in 

 front of it, but never another vein. 



Subcosta. — In all the known orders of insects subcosta is immediately 

 recognizable as a concave vein, that is, it lies at the foot of a trough 

 in the surface of the wing, and its cavity is mainly below the level of 

 the wing-membrane. The second vein from the costal edge in all the 

 Coleoptera is so formed, and may be safely labelled subcosta. It 

 contains a strong trachea in all the forms studied (the one labeled "C" 

 by Comstock and Needham, who overlooked costa). 



Radius. — The third vein of the wing is strongly convex, and forms 

 the principal articulation with the thorax, together, that is, with the 

 second axillary sclerite, from which it rises. Its trachea is always 

 strong, and rises from the anterior tracheal trunk (Chapman, in Com- 

 stock's "Wings of Insects") running in front of the wing-process in 

 close proximity to C and Sc. In the Coleoptera the third of the three 

 closely crowded veins at the costal margin of the wing articulates 

 in the proper manner, and contains the most posterior of the tracheae 

 arising from the anterior trunk, in every form studied, from Cicindela 

 to the Cerambycidas. It then is radius. 



Media. — With media a more serious problem arises. Media is 

 highly unstable in the various orders of insects and may associate 

 itself as a branch with either radius or cubitus. In the Coleoptera 

 whose tracheation is most complete, however, (Calosoma, Fig. 2, 

 Dytiscus, Fig. 5, for instance, and some specimens of Tenebrio, Fig. 6), 

 there is an independent trachea that can only be media. In Calosoma 



