74 SMITHSONIAN MISCELLANEOUS COLLECTIONS [VOL. 50 



bristles. In the Tenthredinidae these are very poorly developed and 

 sometimes wholly wanting; in the Ichneumonidse and Chrysididse 

 they are well developed, and they are strongest and stoutest in the 

 Vespidse and Anthophilidae (especially in Bombus). They usually 

 stand in three dense, comb-like groups or rows, the first near the base 

 of the wing (pi. vm, fig. 16), the second before (pi. vn, figs, i, 6 B 2, 

 9; pi. vm, figs. 11, 12, 13), and the third beyond the distal hooks (pi. 

 vii, figs. 1, 6 B 3, 9; pi. vm, figs. 11, 12). These three groups are 

 not always distinctly developed ; the group before the distal hooks is 

 the one most frequently observed and the most highly developed. The 

 marginal bristles are not, like the hooks, restricted to the costal vein, 

 but also attached to the parts of the wing membrane adjacent to the 

 costal vein (pi. ix, fig. 26, B 2). Their direction is similar to that 

 of the subbasal hooks; they inclose an angle of 90 to 180 degrees 

 with the wing surface. These bristles are straight or slightly curved 

 and twisted. In size they considerably exceed the subbasal hooks, 

 attaining a length of 233 microns, while the subbasal hooks are at 

 the most 57 microns long. They are inserted in low ringed ridges 

 on the upper lamella of the wing and possess a narrow axial lumen 

 distally closed. The chitinous spines which, in the Ichneumonidse, 

 Vespidae, and Anthophilidae, often accompany the series of hooks in 

 the frenal region (pi. ix, figs. 20, 22, 23, Z 1), are also to be consid- 

 ered as marginal bristles of this kind. 



EORE WING 



The posterior margin of the fore wing is recurved and folded in, 

 so as to form a groove. Into this groove the hooks of the hind wing 

 are inserted (pi. ix, figs. 19-26, R i). In the Anthophilidae, Fos- 

 sores, and Vespidae a convex bulging of the upper side of the wing 

 is connected with this more or less highly developed plicature of its 

 posterior margin (pi. ix, figs. 22-26). The plicature and the groove 

 produced by it extend over the proximal half of the hind margin 

 of the wing, and terminated distally at the place where the 

 anal vein reaches the margin of the wing. Here the groove ends 

 abruptly in a knob. Towards the wing basis this plicature flattens 

 out. In forms possessing subbasal hooks closely approximated to 

 the base of the wing the plicature (groove) is deeper at the place 

 opposite these hooks, but there never is, as stated by Staveley (i860, 

 p. 135), a second groove near the base of the wing separated from 

 the distal one by a tract of unfolded wing margin. The plicated 

 chitin forming the groove is much darker than that of other parts 

 of the wing, and the parts of both the lamellae composing the wing 



