128 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 1 37 



we know of a few instances where muscle attachments have been 

 shifted between parts that could never have been contiguous, this 

 seems to have occurred very rarely. It is probable, therefore, that 

 only a developmental investigation offers hope of solving the problem 

 at issue here. However, it is worth noting that a phasmid, Megacrania, 

 actually has two transverse muscles of the third intersegment (Maki, 

 1935) : No. 140, which is my fuz-fu^, and hence interpreted here as 

 the equal of ^sps-ftis ; and No. 2^4, which is ^ils-pls, interpreted by 

 me as derived from ^sps-^ils. 



b. Oblique spinal muscles of the furca and intersegmental latero- 

 sternites: 



3. A muscle from each spina to the preceding furca was character- 

 istic of the early hexapods, to judge by the wide representation of such 

 muscles among existing orders (table i). However, a tendency toward 

 modification and loss of these muscles is also apparent. Though all 

 three muscles are lacking only in higher Diptera and adult Coleoptera, 

 one or another of them has disappeared without trace in all but seven 

 orders, and their occurrence elsewhere may vary with the species. 



In many instances, loss of the spinasternal attachment has evi- 

 dently converted the formerly paired muscles, isps-fiti, etc., into a 

 single band, fux-fih, etc. (see, for example, Badonnel, 1934, on Sten- 

 opsocus). Moreover, since the f ureal arms of the same segment are 

 often nearly immovable relative to each other, one finds that the muscu- 

 lar bands, fih-fui, etc., are frequently replaced by ligamentous straps, 

 or even (in Odonata, some Hymenoptera) by sclerotized braces. For 

 the details in most orders, reference will have to be made to the list of 

 original sources above ; but we would reemphasize here our conviction 

 that the so-called interfurcal muscles fui-fiii, etc., are morphologically 

 distinct from the true transverse intersegmental muscles, such as isps- 

 lils or isps-epso, and that the interfurcal muscles are most probably 

 derived from the type isps-fui, etc. 



As explained in section 2 above, we have chosen tentatively to inter- 

 pret the muscle /// trm 2 of some Mallophaga (Mayer, 1954), which 

 has the form ^sps-fns as really representing ^sps-^ils; if this view is 



