52 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 82 



tier (1923) than with the description of the muscles of Gryllus domes- 

 ticus given by Voss ( 1905). The musculature of the cricket is in some 

 respects more elaborate than that of the locust ; but the extra fibers 

 constitute small and apparently secondary muscles that are not defi- 

 nitely repeated in insects generally. The account of the musculature of 

 Gryllus pennsyhanicus given by DuPorte (1920) contains inaccura- 

 cies, especially with regard to the muscles of the legs ; the leg muscles 

 of Gryllus are in no essential way diflFerent from those of Dissosteira. 



No attempt will be made in this paper to homologize the muscles of 

 Dissosteira with those of other insects, or to correlate them with the 

 muscles described by other writers, since this would add too much to 

 the size of the paper. The student, however, should consult the recent 

 descriptions of the thoracic musculature of insects contained in the 

 works of Bauer (1910, 1924, adult Dytiscus), Speyer (1922, 1924, 

 larval Dytiscus), Carpentier (1923, Acheta campestris and Tachy- 

 cinus asynanwnis), Weber (1927, Tenthrcdimdae; 1924, 1928, Lepi- 

 doptera ; 1928a, Aphis fabae; 1929, Psylla mall), and Morison (1927, 

 Apis mellifera). Berlese's (1909) review of the musculature of in- 

 sects will need some revision in the light of more extensive compara- 

 tive studies of insect muscles ; but a general myology of insects can 

 not yet be undertaken since we need more extensive information con- 

 cerning such groups as Apterygota, Plecoptera, and Neuroptera. 



The terminology of insect musculature offers some difficulty for the 

 reasons that in different species the number of muscles in a functional 

 group is variable, the attachments may shift from one point to another, 

 and the functions of muscles undoubtedly homologous are often 

 changed as a consequence of altered relations in the skeletal parts. In 

 the following description of the thoracic musculature of the grass- 

 hopper individual muscles are designated numerically for convenience 

 of reference only, and the series of numbers {46 to 139) follows the 

 enumeration of the head muscles of Dissosteira given in a former 

 paper by the writer (1928). 



Dissection of the thoracic muscles is simplified when the general 

 plan of the segmental musculature is understood. The thoracic mus- 

 cles of insects fall into a few major groups which, in a general way, are 

 as follows: (i) dorsal body muscles; (2) ventral body muscles; (3) 

 tergo-sternal muscles; (4) special wing muscles; (5) pleuro-sternal 

 muscles; (6) coxal wing muscles; (7) body leg muscles; (8) muscles 

 of the leg segments ; (9) muscles of the spiracles. In addition there 

 are the muscles of the neck plates, and often oblique, lateral interseg- 

 mental muscles. 



