6o SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 82 



extensor of the wing (fig. 49, M'), having its dorsal insertion on the 

 basalar plates of the adult ; the second is the depressor-extensor (M") 

 with its insertions on the subalar plate. Associated with the first is a 

 large muscle (£) arising ventrally on the sternum. These three 

 epipleural muscles (£, M', M") together with the wing flexor {D) 

 constitute the so-called direct zving muscles, though only the flexor is 

 a true wing muscle. 



The ventral muscles of the pterothorax are small ; those of the meso- 

 thorax (figs. 34, 35, 60, 8/, 88) serve to move the prothorax ; those of 

 the metathorax {116, iiy) can have but little motor function, since 

 the mesothorax and metathorax are immovable on each other, and 

 they are reduced mostly to tendinous strands. The muscles of the mid- 

 dle and hind legs are essentially the same as those of the prothoracic 

 leg, but the muscles of the hind tibia are particularly large and not 

 of the same relative size as those of the fore and middle legs. 



A first dissection of the pterothoracic musculature should be made 

 from the median plane of the body in a specimen cut into lateral halves 

 (fig. 34) from which the alimentary canal and other visceral tissues 

 have been removed. 



THE MESOTHORACIC MUSCLES 



81. Lonffitudinal dorsal muscles (fig. 34). — A large mass of fibers 

 in each side of upper median part of mesothorax, attached anteriorly 

 on lobes of first phragma (iPh) and posteriorly on middle phragma. 



82. Oblique dorsal muscles (not shown in figures). — A small mus- 

 cle laterad of longitudinal dorsals ; arising on lateral part of scutum, 

 extending posteriorly and ventrally to insertion on outer part of mid- 

 dle phragma. 



8 J. First tergo-sternal muscle (fig. 34). — Attached dorsally on pos- 

 terior part of lateral prescutal lobe ; attached ventrally on anterior part 

 of mesosternum. 



84. Second tergo-sternal muscle (fig. 34) . — A very large muscle im- 

 mediately posterior to 8j ; attached dorsally by inner branch on middle 

 of lateral scutal area, and by outer branch on marginal lobe of scutum 

 behind posterior articulation of first axillary ; attached ventrally on 

 mesosternum before inner margin of coxal cavity. 



8j. Plcuro-alar muscle: flexor of the wing (fig. 37 A). — This mus- 

 cle lies laterad of the series of dorsoventral muscles in the side of the 

 segment and may be noted after the latter are removed. It arises by 

 a broad base on upper part of pleural ridge (PIR), and goes dorsally 

 and posteriorly between p8 and pp into wing base where it is inserted 

 on the third axillary (fig. 49, jAx). 



