INSECT SPINASTERNAL MUSCULATURE — CIIADWICK II9 



musculature, although helpful information on this and other thysanu- 

 rans is given in the reports of Maki (1938), Argilas (1941), Barlet 

 (1946, 1948, 1949, 1950), Carpentier (1946), Chaudonneret (1950), 

 and Carpentier and Barlet (1951), among others; and for Collem- 

 hola by Denis (1928), Maki (1938), and Carpentier (1947, 1949). 

 Maki (1938) also describes a dipluran, Lepidocampa, but leaves one 

 in doubt as to essential skeletal details ; and there seems likewise to 

 have been no suitable study of a proturan. Data useful for our pres- 

 ent purpose are also lacking for the following Pterygota : Diploglos- 

 sata, Zoraptera, Anopleura, Strepsiptera, Raphidiodea, and Siphonap- 

 tera ; and knowledge of some of the other winged orders is at present 

 restricted to the adult form of a single species. From the point of 

 view of the present study, there has been no adequately extended 

 investigation of the embryogeny of any insect, though it is apparent 

 that certain questions as to structural homologies will be answerable 

 only in the light of such information. 



Our analysis will therefore be confined largely to the Thysanura 

 and the 24 pterygote orders for which reasonably complete and ac- 

 curate observations are available, with only occasional allusions to 

 reports on other insects. When these missing groups, particularly 

 among the Apterygota, can be included, the number of known spina- 

 sternal muscles will certainly be increased to some extent. However, 

 the general pattern of these muscles emerges quite clearly from the 

 data already at hand. 



Since it is not proposed to describe the complete spinasternal muscu- 

 lature order by order, the following summary of the sources selected 

 for this study may be helpful. Unless otherwise noted, the works 

 cited concern adult insects. 



Thysanura. Maki, 1938 {Lepisma, Pedetontus) ; Barlet, 1951, 1953, 1954 



(Lepisma) . 

 CoLLEMBOLA. Maki, 1938 (Ncanura, Folsomia). 

 Blattariae. Carbonell, 1947 (Periplaneta) ; Chadwick, 1957 (19 spp., nymphs 



and adults, ventral intersegmental muscles only). 

 CoLEOPTERA. Bauer, 1910 (Dytiscus) ; Speyer, 1922 (Dytisctis larva) ; Murray 



and Tiegs, 1935 (Calandra, larva and adult) ; Maki, 1938 (7 spp.) ; Josting, 



1942 (Tenebrio larva) ; Chadwick, unpublished (Cybister larva). 

 Dermaptera. Maki, 1938 {Anisolabis, Labia) ; Chadwick, unpublished {For- 



ficiila). 

 DiPTERA. Samtleben, 1929 (culicid larvae) ; Mihaiyi, 193S {Miisca) ; Maki, 



1938 (S spp.) ; Williams and Williams, 1943 (Drosophila repleta) ; Zalokar, 



1947 (D. melanogaster) ; Bonhag, 1949 {Tabaniis) ; Miller, 1950 {D. melano- 



gaster). 

 Embiodea. Verhoeff, 1904 (Embia) ; Maki, 1938 (Oligoloma). 



