. Smithsonian miscellaneous collections. prescutal sutures is differentiated topographically into alarge anterior scutal region (fig. 22 A, Set), a median, posterior, tri-angular scutellar region {Sel), two small, lateral, posterior scutal re-gions {set, set), and a posteriormost, deflected marginal region {Rd).The structure here presented is quite different in appearance fromthat of a typical wing-bearing tergum (fig. 5 A) in which the surface 40 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 82 is divided into scutal and scutellar areas (Set, Scl) by the suture (vs)of an internal V-shaped ridge
. Smithsonian miscellaneous collections. prescutal sutures is differentiated topographically into alarge anterior scutal region (fig. 22 A, Set), a median, posterior, tri-angular scutellar region {Sel), two small, lateral, posterior scutal re-gions {set, set), and a posteriormost, deflected marginal region {Rd).The structure here presented is quite different in appearance fromthat of a typical wing-bearing tergum (fig. 5 A) in which the surface 40 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 82 is divided into scutal and scutellar areas (Set, Scl) by the suture (vs)of an internal V-shaped ridge (B, VR), the arms of which are con-vergent forward from the posterior lateral angles of the tergum. In the Acrididae the V-shaped endotergal ridge (fig. 22 B, VR)is almost obliterated, and the tergum is braced by two secondary ridges,one on each side (s), that converge posteriorly from the posteriorlateral margins of the scutal area and intercept the arms of the rudi-mentary V-ridge (VR). The altered structure of the acridid tergum Psc. Rd Fig. 23.—Diagram of the structure of a wing-bearing tergum of Acrididae. The prescutal suture (ps) is either continuous, or suppressed medially; theusual V-ridge and its suture (vs) are partially suppressed and subordinated to asecondary ridge of similar shape but having its arms (s, s) convergent posteriorly. may be expressed diagrammatically as in figure 23, where the sup-pressed suture (vs) of the obsolete V-ridge is crossed by the dominantsuture (s) of a secondary ridge of similar shape but having its armsconvergent posteriorly. Thus the scutum consists of a principal an-terior scutal area (Set) and of two small postero-lateral scutal areas(set, set) ; and the scutellum is divided into a median scutellar area(Sel) and two lateral scutellar areas (sel, sel), including the posteriorfold of the tergum (Rd). The evolution of this condition can be tracedin other Orthoptera from the primary structure which occurs in theBlattidae. A similar mo
Size: 1637px × 1527px
Photo credit: © The Reading Room / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookauthorsm, bookcentury1800, bookdecade1860, booksubjectscience
