404 THE INSECTA. "§. 326. 



furthermore, from the others, in their transverse striae being less distinct, and 

 their fibrillae being more easily observed; indeed, with most species, these 

 last show a tendency to separate even from the least pressure, while those 

 of the other voluntary muscles are very compactly united together. ^-^ 



The muscles are attached directly upon the cutaneous skeleton, as with 

 the Crustacea. In the extremities, only, do there appear tobe tendons; 

 but these are merely very long, flattened processes of the skeleton, situated 

 in the axis of the articles of the extremities. They serve as points of 

 attachment to short muscular fasciculi which are there obliquely inserted^ 

 after having ariseu from the inner surface of the articles. With adult 

 insects, the segments of the body are only slightly movable, and have but 

 few muscles. But with the larvae, whose extremities are rudimentary, or 

 even wholly wanting, there is a very prominent nmscular system situated 

 directly beneath the skin, and composed often of several layers of flattened 

 fasciculi. ^'^^ 



§ 326. 



The Locomotive organs, properly speaking, of the Insecta, are the legs 

 and the wings. The true legs never exceed three pairs, and are inserted 

 upon the first three segments back of the head — Prothorax, MesothoraXy 

 Metathorax. Each leg is divided into a Coxa, a Trochanter, a Femury 

 a Tibia, and a Tarstis. The tarsus is divided into several articles, the 

 number of which reaches even five. The form of these legs varies infinitely 

 according to the mode of life of each species. The most common are those 

 io which are usually given the names : Pedes cur surd, arnhulatorii, gressoriiy 



2 This is so with tlie Diptera, Hemiptera, and Straus, Consid. &c. p. 140, PI. III. IV. {Melolon- . 

 Hymenoptera, with the muscles of whose wings the tha xxtlgaris). 



elements may be very easily separated.* Reference may be also made to the works of 



3 Lyonet (Traite, &c., p. 114, PI. VI.-VIII.) has Meckel (System, &c., III. p. 22), Cuvier (LeQons, 

 given a very detailed account of the muscles of the &c. II. p. 64), hurmeister (Handb. &c. I. p. 267), 

 larva of Cossus. See also Newport, Philos. Lacordaire (Introduct. ä I'Entomol. II. p. 249), 

 Transact. 1836, p. 537, PI. XXVII. (the cutaneous and of Newport (Cyclopaed. &c. loc. cit. p. 934). 

 muscles of the larva of Sphinx ligustri), and 



* [ § 325, note 2.] The delicate and beautiful ially) with the highest and best microscopic powers, 



structure of the thoracic muscles of some of the In- The discs composing the primitive fibrillae, easily 



secta, has been carefully studied of late, and has separate and may be studied by themselves. But, 



aided not a little in the elucidation of the histology with the best powers, I have been unable to observe- 



of the muscular tissue. See Lebert, Kecherches in them anything but that each disc is a solid, 



sur la formation des muscles, &c., in the Ann. d So. homogeneous light-refracting body. The fibrilla 



Nat. XIII. 1850, p. 182-195, PI. VII. fig. 18-27 ; appears to be formed by the aggregation of these 



but especially Aubert, Ueber die eigeuthiimliche discs in a linear series and with regular inter- 



structur der Thora.xmuskeln der Insekten, in Sie- spaces ; no sheath, by which these discs would be 



bold and Külliker\i Zeitsch. IV. 1853, p. 388. retained in a row, was observed. Contraction of 



This last-mentioned naturalist states that he has the fibrilla takes place by an approximation of the 

 observed a new form of muscle-element in the discs to each other, and the consequent greater or 

 thorax of the LibelluUdae, consisting of primitive less disappearance of the interspaces. These phe- 

 muscular bands by means of which, with a beaker- nomena can be easily observed, and, it may b& 

 shaped apparatus, the wings are moved. These added, there are often seen isolated fibrillae con- 

 fibres consist of flattened riband-like bands, striated trading and relaxing, thus showing that the real 

 on their borders as well as on their flat surface. jjlienomenon of muscular contraction, does not de- 



I have recently studied the elements of the pend upon the nervous system, however much the 



thoracic muscles of many Diptera ( C«/c a;, espec- action of this last n;ay serve as a stinmlant. Ed. 



