. Smithsonian miscellaneous collections. or muscle of the leg base (fig. 11, /) retains its connection withthe subcoxa in the more generalized pterygote insects, being insertedon the trochantinal sclerite of the subcoxa (Tn) except when thetrochantin is lost, the muscle then having its insertion on the anteriorangle of the coxal base. The remotor muscle (J), which may be repre-sented by several fiber bundles, is always inserted on the coxa or oncoxal apodemes. The anterior and posterior sternal muscles (K, L)arise on the sterna or the sternal apophysis, or on the spinasternum. i6 SMITHSONIAN M
. Smithsonian miscellaneous collections. or muscle of the leg base (fig. 11, /) retains its connection withthe subcoxa in the more generalized pterygote insects, being insertedon the trochantinal sclerite of the subcoxa (Tn) except when thetrochantin is lost, the muscle then having its insertion on the anteriorangle of the coxal base. The remotor muscle (J), which may be repre-sented by several fiber bundles, is always inserted on the coxa or oncoxal apodemes. The anterior and posterior sternal muscles (K, L)arise on the sterna or the sternal apophysis, or on the spinasternum. i6 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 82 The median coxal muscles are represented in insects by both dorsal(M) and ventral (N) fibers. In the wing-bearing segments of ptery-gote insects the first comprise three distinct groups of abductor fibers(M, M, M) arising dorsally on the pleuron, and inserted ventrallyon the coxa both anterior and posterior to the dorsal articulation ofthe latter {c). The second and third muscles of this group {M, M) Sex. Ptar Fig. —Thoracic pleural sclerites of Apterygota. A, lateral view of left side of mesothorax of Acercntomon doderoi (fromBerlese, 1910). B, thorax, base of head, and base of abdomen of Isotoma sp.(from Ewing, 1928). C, left mesothoracic leg turned forward, and lateral re-gion of mesothorax of Acerentulus barberi (from Ewing, 1928). c, dorsal articulation of coxa; , coxa; d, ventral articulation of coxa; Fm,femur; H, head; IT, I IT, first and second abdominal terga; Ptar, pretarsus;S, sternum; Sex, subcoxa; Ti, T2, Ts, thoracic terga; Tar, tarsus; Tb, tibia;Tr, trochanter. become wing muscles in the adult by the partial or complete detach-ment of the epipleural areas on which they arise to form the basalarand subalar plates of the wing base. The ventral median muscle of thecoxa (A^) is present in insects that lack a ventral coxal articulation;it arises on the sternal apophysis and functions as a coxal adductor. In the Apterygota the
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