. Smithsonian miscellaneous collections. oxal parts of the latter (fig. 30 A).In the nymph of Dissosteira and of other Acrididae, as already noted,the pleural plates of the mesothorax and metathorax (fig. 27 A, PI2,PI3) are distinctly separate from the sterna (S2, S3), and the pre-coxal part of each pleuron is extended ventrally and posteriorly as aslender arm {Ls, Ls) between the sternum and the coxal arms are clearly remnants of the infra-coxal arcs of the sub- 48 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 82 coxae (fig. 18 B). In the adult grasshopper they form the ventral rims
. Smithsonian miscellaneous collections. oxal parts of the latter (fig. 30 A).In the nymph of Dissosteira and of other Acrididae, as already noted,the pleural plates of the mesothorax and metathorax (fig. 27 A, PI2,PI3) are distinctly separate from the sterna (S2, S3), and the pre-coxal part of each pleuron is extended ventrally and posteriorly as aslender arm {Ls, Ls) between the sternum and the coxal arms are clearly remnants of the infra-coxal arcs of the sub- 48 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 82 coxae (fig. 18 B). In the adult grasshopper they form the ventral rimsof the coxal cavities, that of the mesothorax becoming a weaklysclerotized plate, that of the mesothorax a membranous fold. Thedefinitive sterna of the pterothorax in the Acrididae, therefore, do notappear to contain subcoxal laterosternal elements as integral parts oftheir areas. In the adult of Dissosteira the pleuro-sternal suture(fig. 30 A, r) is obsolete in the mesothorax anterior to the coxa, butremains distinct in the Fig. 30.—Pterothoracic sterna and the base of the abdomen of Dissosteira. A, general view of pterothoracic sterna and first two abdominal , diagram of probable structure of mesosternum. C, diagram of probable struc-ture of metasternum. D, diagram of structure of first abdominal sternum. acs, antecostal suture of first abdominal sternum; Bs, basisternum; Cx, coxa;CxC, coxal cavity; IS, IIS, first and second abdominal sterna; ;, prepectalsuture; k, furcal suture; Pc, precosta; Ppct, prepectus; r, r, pleuro-sternalsutures; sa, sa, roots of sternal apophyses; SI, sternellum; t, t, infra-coxal lobesof metasternum. The mesosternum of Dissosteira is a broad plate (fig. 30 A, Bs2, Sk)bounded laterally by the obsolete lines of the pleuro-sternal sutures(r) and the rims of the coxal cavities. Its anterior edge is slightlyconvex ; its posterior border is deeply emarginated to receive a medianrectangular extension of the mesosternum (Bss) which i
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Keywords: ., bookauthorsm, bookcentury1800, bookdecade1860, booksubjectscience
