is attached to the upper margin of the claw. Besides these muscles, which are common to the joints of the tarsus, there are two others belonging to the claw, situated in the last joint. The first of these, the _extensor_ (_m_), is short, and occupies the superior portion of the last phalanx of the tarsus, and the other, the _flexor_ (_n_), is a much longer penniform muscle, which occupies nearly the whole of the upper and under surface of the posterior part of the phalanx, and is attached, like the long flexor of the tarsus, to the inferior part of the claw.” [Illustration: FIG. 233.—Muscles of the fore leg of _Melolontha vulgaris_: _a_, _b_, _c_, three divisions of the extensor of the trochanter; _d_, flexor,—_e_, abductor, of the trochanter; _f_, extensor of the femur; _g_, flexor of the femur; _h_, extensor of the tibia; _i_, flexor of the tibia; _l_, tendon attached to the lower edge of the claw (_g_); _m_, extensor,—_n_, flexor, of the claw.—After Straus-Durckheim, from Newport. ] These are the muscles of the prothorax, and its organs of locomotion. The reader is referred for a further account of the muscles of the hinder thoracic and of the abdominal segments to Straus-Durckheim’s original work. =Minute structure of the muscles.=—The muscular fibres of insects are striated (Figs. 235–238), even those of the alimentary canal; the only notable exception being the alary muscles of the pericardial septum, while Lowne states that certain of the thoracic muscles of the blow-fly are not striated (Miall and Denny). [Illustration: FIG. 234.-Section through the prothorax of _Diapheromera femoratum_: _prov_, proventriculus; _tr_, trachea; _n. c_, nervous cord; _s. gl_, salivary gland; _hyp_, hypodermis; _ur. t_, urinary tube; _ht_, heart; _m_, _m″_, _m‴_, muscles for lowering and raising the tergum; _m′_, another muscle, its use unknown. ] [Illustration: FIG. 235.—Striated muscular fibre of Hydrophilus: _A_ and _B_, two fibrillæ in a state of extension; _a_, thick disk; _b_, thin disk; _c_, intermediate space. _C_, _D_, portion of the same fibrillæ seen by moving the objective farther away and using a small diaphragm; _n_, thick; _c_, thin disk. × 2000 diam.—After Ranvier, from Perrier. _E_ after Gehuchten, from Lang. ]