INSECT SPINASTERNAL MUSCULATURE — CHADWICK 1 25 



Table I. — (Continued) 



2sl'S-fHi Thysanura; Blattariae; Dennaptcra; Embiodea ; Grylloblattodea; 



Isoptera; Megaloptera, /, a; Odonata, n, a; Orthoptera; Plecoptera, 

 n, a; Psocoptera. 



3sps-iils Coleoptera, /; Megaloptera, /; Neuroptera, /. 



2sps-c.r$ Thysanura; Blattariae; Coleoptera, /; Grylloblattodea; Isoptera; 

 Mantodea; Megaloptera, /; Neuroptera, /; Odonata, n, a; Orthop- 

 tera; Plecoptera, n, a; Psocoptera. 



2sps-cxs Thysanura; Blattariae; Coleoptera, /; Dermaptera; Grylloblatto- 

 dea; Isoptera; Megaloptera, /; Neuroptera, /; Odonata, n, a; 

 Orthoptera; Plecoptera, n. a; Psocoptera. 



2Sps-3sps Thysanura; Blattariae; Mantodea. 



Ssps-sils Thysanura ; Coleoptera, /; Mallophaga ; Mecoptera ; Megaloptera, 

 /; Phasmatodea. 



Ssps-jtis Thysanura; Blattariae; Ephemeroptera ; Isoptera; Mallophaga; 

 Mantodea; Mecoptera; Megaloptera, /, a; Neuroptera, a; Orthop- 

 tera ; Phasmatodea ; Psocoptera. 



Ssps-Sx Thysanura; Megaloptera, /. 



Ssps-Iils Thysanura; Blattariae; Isoptera; Mantodea; Megaloptera, /, a; 

 Orthoptera ; Psocoptera. 



3sps-2ils Coleoptera /. 



3sps-cxa Thysanura; Coleoptera, /; Grylloblattodea; Isoptera; Mantodea. 



Ssps-Isps Thysanura ? ; Blattariae ? 



Glossary of abbreviations 



ax axillary sclerite 



cv cervical sclerite 



ex coxa 



cps episternum 



fn furca, furcal arm, segmental sternal apophysis 



i7.f intersegmental laterosternite 



lig intersegmental transverse ligament 



pi pleuron 



J segmental sternum 



sps spinasternite or spina 



X cruciate, used of a muscle whose origin and insertion are on oppo- 

 site sides of the midline 



DISCUSSION OF MUSCLE TYPES 



The spinasternal muscles considered here include four main types : 

 (a) the transverse muscles ; (b) oblique muscles attached on the furcal 

 arms (/w) or on the intersegmental laterosternites (Us) ; (c) spina- 

 coxal muscles; and (d) spinaspinal muscles. In some species, spina- 

 sternal muscles with attachments other than those just indicated are 

 found, but these can usually be interpreted as derived from one of the 

 types already listed. Exceptions are the spinatergal muscles of some 

 Apterygota (Maki, 1938; Barlet, 1953, 1954) and the spinal depres- 



