NO. 6 GRASSHOPPER ABDOMEN SNODGRASS 3I 



2^2. Transverse muscle (fig. 14). — An unpaired, straplike trans- 

 verse muscle, present only in the female, lying dorsal to the base of 

 the ovipositor and attached laterally on the ends of the tenth tergum. 

 (Only the ends of this muscle shown in the figure.) 



MUSCLES OF THE ELEVENTH SEGMENT 



The musculature of the eleventh segment includes muscles from the 

 epiproct to the cerci and paraprocts. and muscles from the epiproct and 

 paraprocts to the circumanal membrane. 



2p^. Adductor of the cercus (figs. 7 D, 14). — A slender muscle 

 arising anteromedially on the epiproct, inserted on the inner extremity 

 of the basal lobe of the cercus. 



2Cf4. Adductor of the paraproct (fig. 14). — A large muscle arising 

 medially on the epiproct just behind 2pj in the female, extending 

 laterally and posteriorly to its insertion on the upper part of the para- 

 proct behind the base of the cercus. In the male this muscle arises 

 mesad of 2g^ and underlaps the base of the latter. 



2g5. Dorsal dilator of the anus. — A median unpaired muscle arising 

 centrally on the epiproct (fig. 14), its fibers spreading distally to their 

 insertions on the dorsal part of the circumanal membrane (fig. 16 A). 



2q6. Lateral dilator of the anus. — Origin on the paraproct near the 

 base of the outer wall of the latter (fig. 14) ; extends dorsally, mesally, 

 and posteriorly to its insertion ventrolaterally on the rectum just 

 within the anus (fig. 16 A). 



THE TRANSVERSE MUSCLES 



The transverse muscles of the abdomen comprise dorsal transverse 

 muscles (fig. 10 B, td) and ventral transverse muscles (tv). The 

 former are always the muscles of the dorsal diaphragm ; the ventral 

 muscles may consist of segmentally individual bundles of transverse 

 fibers, but in the Acrididae they form a continuous muscular sheet, or 

 ventral diaphragm. The muscle uniting the opposite ends of the tenth 

 tergum in the female of Dissosteira (fig. 14, 292) is literally a dorsal 

 transverse muscle, but it evidently does not belong to the series of 

 diaphragm muscles. 



III. THE DIAPHRAGMS AND THE DORSAL BLOOD VESSEL 



The so-called diaphragms of insects are transverse dorsal and ven- 

 tral partitions of the body cavity that separate from the axial pervis- 

 ceral sinus (fig. 10 B, PvS) a dorsal sinus, or pericardial cavity (DS), 



