. Smithsonian miscellaneous collections. orax and the metathorax is distinctly sepa-rated from the sternum ; in the nymph of Gryllus (B) a precoxal plate() is separated from the pleuron and intervenes between theepisternum and the sternum. The episternum of the mesothorax ofDissosteira (fig. 26, EpSo) is marked anteriorly by a submarginal NO. 2 THORACIC MECHANISM OF A GRASSHOPPER SNODGRASS 45 suture (/) which is continuous through the anterior part of the meso-sternum (So) and sets off from the sternum and the two episterna anarrow anterior marginal piece, or prepcctus (Ppct), which is ana
. Smithsonian miscellaneous collections. orax and the metathorax is distinctly sepa-rated from the sternum ; in the nymph of Gryllus (B) a precoxal plate() is separated from the pleuron and intervenes between theepisternum and the sternum. The episternum of the mesothorax ofDissosteira (fig. 26, EpSo) is marked anteriorly by a submarginal NO. 2 THORACIC MECHANISM OF A GRASSHOPPER SNODGRASS 45 suture (/) which is continuous through the anterior part of the meso-sternum (So) and sets off from the sternum and the two episterna anarrow anterior marginal piece, or prepcctus (Ppct), which is analo-gous to the similar sclerite of the Ichneumonidae and some otherHymenoptera. To the jxjsterior margin of the epimeron of the meta-thorax {Epm^) is attached the large lateral extension of the meta-thoracic postnotum {PN3). The two pairs of spiracles of the thorax are presumably the meso-thoracic spiracles and the metathoracic spiracles, each pair being dis-placed anteriorly. The first spiracle on each side (fig. 26, Sp2^ is PIS .D PIR. Fig. 27.—Pterothoracic pleura of orthopteran nymphs. A, pterothoracic pleura of an acridid nymph, showing laterosternal arms ofpleura (Ls) separated from sterna (52, Ss) by the pleuro-sternal sutures (r, r). B, mesopleurou and coxa of young nymph of Gryllus assimilis, showing a dis-tinct precoxal sclerite (Acx) between episternum (Eps) and sternum (S).C, inner view of B, showing the basalar and subalar muscles of the nymph(M, M) attached dorsally on edges of episternum and epimeron, respectively. situated laterally in the intersegmental membrane between the pro-thorax and the mesothorax, where it is covered by the posterior foldof the protergum. The second spiracle (fig. 26, Spz) appears in theadult to lie in the lower posterior angle of the mesepimeron {Epm^.)just above the base of the middle leg, and anterior to the fold betweenthe mesothorax and the metathorax (fig. 28), but in the nymph(fig. 27 A) it occurs in the intersegmental fold. The
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Keywords: ., bookauthorsm, bookcentury1800, bookdecade1860, booksubjectscience
