NO. II THORACIC MUSCLES OF COCKROACHES — CHADWICK 



Table i. — S pinastcrnal muscles of cockroaches 



In this composite list, muscles that appear on the same horizontal line are 

 considered serially homologous. Question marks indicate uncertain homologies. 

 Symbols such as M./o, C103 refer to the numbers given the corresponding mus- 

 cles in P. australasiae by Maki (1938) and in P. americana by Carbonell (1947). 

 Each of the 19 species investigated here has all muscles shown in the table, 

 except as stated in the notes below or in the text. For muscles without spinaster- 

 nal attachments, see table 2. 



Footnote 

 number First spina Second spina "Third spina" 



i,a isps-iils 2sps-3ils 



I ,b isps-epst 2sps-cpSs — 



M40; C103 M74; C149 



2 isps-fui — "3sps"-jus 



M8; C99 M41 M.105 (partiin) 



3 — 2SpS-jUt — 



Cioi 



4 isps-fut 2sps-jus "i "3sps"-sjiA 



C104 M73; C151 M104; C191 ? 



5 — 2SpS-SiiA — 



CI89 



6 isps-cxi 2sps-cxt ? fua-cxs post. rot. (partim) 



M24, 25; C98 M56; C134 M88, 89; C171 



7 ISpS-CXt 2SpS-CX3 — 



CI05 CI73 



8 isps-2sps 2sps-3sps ? "3sps"-ventr. diaphr. 



M39; C106 M72; C152 M105 (partim) 



''■ Cryptocercus has both i,a and i,b; other species i,Ij only. The abdominal transverse 

 muscle, Sji^-Sjjji (Mm, is a serial homolog. 



2 Muscle zsps-fut is lacking; Maki's record (M^/) is probably an error of transcription. 

 (See text.) 



' No comment. 



* Carbonell (1947, p. 20) describes muscle /p/ in P. americana as follows: "Oblique ven- 

 tral muscle. . . . From the base o£ the sternal arm to the anterior edge of the first [sic!] 

 abdominal sternum." 



' Abdominal insertion wholly or partly on Sjjj^ in Eurycotis, Macropanesthia, Neostylopyga, 

 and Periplaneta brunnca. (See text.) 



* Several species have two definitive muscles, isps-cxi, one of which is probably equivalent 

 to the eps,-fUjX of other species. (See figures and text.) In listing two f ureal posterior 

 rotators of the third coxa, Maki (1938) suggests that one of them may be serially homologous 

 with the spinal posterior rotators of the other legs. (See text for discussion.) 



"< Blabcrus, Diploptera, Cryptocercus, Lcucophaca, Macropanesthia, Nauphoeta, and Pyc- 

 noscelus lack isps-cx^; the last five genera also lack 2sps-cXy 



* The fibers from "ssps" to the ventral diaphragm were not found in several species, but 

 were possibly destroyed during dissection in some of these. 



