INSliCTA. 



94 1 



before the retractor. The other retractor (g) 

 arises from tin: anterior superior boundary of 

 the pronotum, and passinn downward* is in- 

 serted into the jugular plate between the larger 

 levator and the tlcxoi- capitis. 



The muscles proper to the prothorax consist 

 of four pairs, by which il is united to tlie suc- 

 ceeding segments. The first of these, the 

 superior retractor, retractor prutliurufis s/ri<r 

 (A), ansi-s by a broad tle-hy head from the 

 anterior external margin of the pronotum, and 

 passing directly backwards is inserted by a 

 tendon into the prophragma a little on one side 

 of the median line. The next muscle of im- 

 portance, the iitferiorretrattor(i), arises from the 

 anterior border of the medi-furca, and is united 

 to the posterior of the ante-furca, thus forming 

 with that muscle part of the great recti of the 

 larva. This muscle must be considered a* tin- 

 proper depressor of the prothorax. The eleva- 

 tor prothnracis (k) is narrow, pyramidal, and 

 arises fleshy from the lateral surface of the 

 prophragma. It passes downwards and i.s 

 attached by a narrow tendon to the superior 

 portion of the anle-furca. The rotatnres pro- 

 tliorncis are the largest of all the muscles of 

 this segment. They arise, one on each side (/), 

 by a narrow head from the posterior part of 

 the pronotum, and passing beneath the pro- 

 phragma are considerably enlarged and attached 

 to the tegument between the two segments, 

 and also to the anterior portion of the mesc- 

 thorax. The remaining muscle proper to the 

 prothorax is the closer of the spiracle, an ex- 

 ceedingly small muscle not shewn in the draw- 

 ing. The other muscles of this segment are 

 those of the legs, which are of considerable 

 size. There are three distinct flexors of the 

 coxa (m, n, o). The first of these arises from 

 the superior lateral border of the pronotum, 

 the second from the superior posterior border, 

 the third from the sides of the prothorax, and the 

 fourth a little nearer posteriorly, and the whole 

 of them are attached by narrow tendons to the 

 sides of the coxa. Hut there is only one 

 extensor muscle to this part. In like manner 

 the extensor of the trochanter is formed of 

 three portions, (jig. 403, a, b, c,) but there is 

 only one flexor (d) and one abductor (e). 

 In the femur there is one extensor (./), a long 

 penniform muscle that occupies the superior 

 part of the thigh, and is attached by a tendon 

 to the anterior posterior margin of the joint, 

 formed by the end of the tibia. There is also 

 but one flexor (g) in the femur, which, like the 

 preceding muscle, is penmfodB, and occupies 

 the inferior portion of the femur, and its 

 tendon is attached to the inferior border of the 

 tibia. In the tilua itself there is also one 

 flexor and one extensor. The flexor (i) occupies 

 the superior portion of the limb, and ends in 

 a long tendon (/) that passes directly through 

 the joints of the tarsus on their inferior surface, 

 and is attached to the inferior margin of the 

 claw (). The crlfusor (It) occupies the infe- 

 rior portion of the tibia and is shorter than the 

 preceding muscle, like which it ends in a long 

 tendon that is attached to the upper margin of 

 the claw, besides these muscles, which are 



Fig. 403. 



Sfiucla of the anterior leg of Melohnlha nlyarit. 

 ( Strum.) 



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 uttruor 

 (m), is short and occupies the superior portion 

 of the last phalanx of the tarsus, and the other, 

 the Jiexor (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. These are the muscles of the pro- 

 thorax and its organs of locomotion, as shewn 

 by Straus, and exemplify the extent unto which 

 the muscular system is developed in perfect 

 insects. The muscles of the other segments of 

 the thorax differ considerably from these in 

 their form and arrangement,, but the length 

 unto which this article has already been carried 

 prevents us from entering particularly into their 

 consideration . The great depressor muscle of the 

 wings, tiiusculta metanoti (fig. 402, x), occupies 

 with its fellow the chief portion of the dorsal 

 surface of the meso- and meta-thorax, and the 

 elevators and pretractors, musculi laterale* me- 

 tanoti (y, v), the lateral superior parts of the 

 same segment, and descending obliquely back- 

 wards are attached to the metaphragma and 

 base of the post-furca. The other muscles 

 which belong to the legs and those that connect 

 the thorax to the abdomen are of considerable 

 size. One of those of the posterior legs, the 

 second flexor (z), is seen immediately behind 

 the muscles of the wings, and the cxteniori 

 (a, n) at the posterior part of the segment. In 

 the abdomen the chief muscles are the dorsal 



