The muscles are whitish or colorless and transparent, those in the thorax being yellowish or pale brown; and of a soft, almost gelatinous consistence. In form they are simply flat and thin, straight, band-like, or in rare cases pyramidal, barrel or feather shaped. They act variously as rotators, elevators, depressors, retractors, protractors, flexors, and extensors. [Illustration: FIG. 231.—Diagram of the muscles and nerves of the ventral surface of the segments in the larva of _Sphinx ligustri_: _A_, _A_, recti muscles; 1, 2, ventral recti muscles (1, recti majores; 2, recti minores); 3, ridge giving origin to recti muscles of one segment, and insertion to the same of the adjoining segment; 4, ridge for attachment of muscle; 5, retractor ventriculi, connecting the mid-intestine with the outer integument of the body. _B_, 6, first oblique,—7, second oblique,—9, 10, third oblique, muscles; 11, fourth oblique,—12. third rectus,—13, fifth oblique,—14, triangularis, muscle; 15, transversus medius; 16, transverse ridge; 17, transversi abdominales; 18, abdominales anteriores; 19, 20, abdominales laterales, some (20) longer than others; 21, obliquus posterior; 22, postero-laterales obliqui; 23, transversus lateralis; 24, second transversus lateralis; 25, retractor spiraculi, or constrictor of the spiracles, attached by a long tendon (26); 27, retractor valvulæ. Nerves: _a_, ganglion,—_c_, transverse nerves, of which _p_ is the first, _q_ the second, _r_ the third, and _s_ the fourth branch; _t_, the main trunk, which crosses the great longitudinal trachea, receives a filament from the transverse nerve (_n_), and divides into two branches (_t_);—some of these branches form a small plexus (_u_); the nerve _t_ divides in two divisions (_p_ and _v_). The second division ends in _w_ and _x_; the branch _q_ divides into _y_ and _z_. For other explanations, see Newport, art. _Insecta_.—After Newport. ] [Illustration: FIG. 232.—Musculature of the European cockchafer, _Melolontha vulgaris_: _a_, _a_, levatores capitis; _b_, depressores capitis; _c_, rotatores capitis; _d_, depressors externi; _e_, retractor or flexor of the jugular plate; _f_, oblique extensor of the jugular plate; _g_, the other retractor of the jugular plate; _h_, retractor prothoracis superior; _i_, inferior retractor, the proper depressor of the prothorax; _k_, elevator prothoracis; _l_, one of the rotatores prothoracis; _m_, _n_, _o_, flexors of the coxa; _x_, great depressor muscle of the wing; _y_, _y_, elevators and protractors attached to the metaphragma and base of the postfurca; _z_, second flexor of hind leg; _a_, _a_, extensors of hind leg; _c_, _c_, dorsal recti of abdomen. _Q_, ejaculatory duct; _R_, penis; _S_, its prepuce. _M_, rectum.—After Straus-Durckheim, from Newport. ]