1922] Forbes: Wing-Venation of Coleoptera 331 



In the Coleoptera, save in the Phytophaga and some LamelHcoms, 

 there is a trachea which sphts off from Cu near its base, then frequently 

 runs obliquely through the membrane, and enters a vein in the outer 

 part of the wing, running with it to the margin (Figs. 3, 5, 6). The 

 concave anal furrow lies close below this trachea. In Cupes (Figs. 4, 12) 

 the whole is represented by a vein, and meets all the qualifications 

 of 1st A (that is, Cus). In higher phytophaga at least, this trachea 

 is completely absent, as shown by a Comparison of Comstock's figures 

 308 to 310, with mine of Tenebrio (Figs. 6, 43); and the corresponding 

 vein of the imago is also absent. 



Second and following anals. — There remain two branched tracheae, 

 and a third which is also bifurcated in the Adephaga, but more com- 

 monly simple. These may be numbered in order: 2d A, 3d A and 4th A. 

 They doubtless represent the anal fan of lower orders, and also the 

 second and third anals, and supporting vein of the jugum in, the 

 Lepidoptera. The first of these is 3-branched at least, as shown plainly 

 in the Buprestidas (Figs. 6a, 34); but the anterior branch, both trachea 

 and vein, is lost in many families, including all the Adephaga, Palpi- 

 cornia and Heteromera; and the posterior branch, save in the Elaters, 

 Lampyrids, and some Buprestidce and Dermestidae, fuses at the apex 

 with the anterior branch of 3d A. 



In this discussion the anals are treated as four in number on account 

 of the tracheal arrangement, and seem to be homologous with the three 

 recognized anals and the jugal brace of the Lepidoptera; but the con- 

 dition in the base of the wing is complex, and comparison with Chauliodes 

 (Fig. 71: a form which shows the same number of terminal anal 

 branches) suggests strongly that the second may be a fusion of an 

 original second and third anal; and that the vein here considered a 

 cross-vein between 2d A end 3d A may really be a fourth branch of 

 2d A ; in several forms it has a trachea. 



The permanent cross-veins. — Certain cross-veins are so constant in 

 higher insects as to become a part of the hypothetical plan. These are 

 the humeral, the arculus, and a series near the middle of the wing 

 (known as discocellulars in the Lepidoptera). The humeral cross vein 

 shows plainly in several Coleoptera as a short fusion of C and Sc, which 

 are everywhere closely parallel. Arculus is plain enough, especially in the 

 Serricorns and Heteromera, (Figs. 65 and 66 for instance) , and has already 

 been discussed as a sector of media. The discocellulars, if present as 

 such at all, are disguised by the folding, and must be discussed among 

 the more problematical veins. 



Stigma. — The stigma or pterostigma is a thickening of the marginal 

 portion of the wing in the neighborhood of the apical part of Sc (802) 

 and Ri. It shows plainly in a great many beetles belonging to the 

 Adephaga, Palpicornia and Staphylinoidea, and will be used below as a 

 means of identifying the distal sector of Ri. 



