20 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. I3I 



There is thus no problem of explaining a shift of their attachments 

 to a segmental site, for no shift has occurred. 



Apart from the structure of the profurca, with its connotations for 

 the evolution of the furcal structures of pterygote insects in general, 

 there is little that is remarkable about the sternal apophyses and 

 their musculature in cockroaches that has not already been touched 

 on in preceding sections. The ventral furcal intersegmental muscles 

 found in the Blattariae may be classified as (a) spinafurcal muscles; 

 (b) furcal muscles from the Us; and (c) furcofurcal muscles, includ- 

 ing muscles with furcal origins and insertions in the head, neck, or 

 abdomen. If the suggestion offered above is correct, that the definitive 

 furcal apophysis is partly of intersegmental nature, a number of other 

 muscles with furcal attachments, such as those of the appendage, may 

 also be primarily intersegmental. However, further work is needed 

 on the details of such relationships, and it seems best to leave them 

 for future consideration. 



Except for muscles with spinasternal attachments (table i), the 

 ventral furcal intersegmental muscles of cockroaches are listed in 

 table 2. 



Furcal muscles from the spinae and Us have been discussed above, 

 particularly under sections i,b, 2,a, and 2,c. Like these muscles, the 

 furcofurcal muscles of blattids can be homologized in considerable 

 detail with those of comparable location in other insects. Readily dis- 

 tinguished in most cockroaches are a usually slender mesal band and 

 a more massive lateral band of both fuj-jua and fug-fug. Components 

 probably homologous with each of these bands can also be identified 

 in many blattids in the muscle fus-SuA, which often includes an addi- 

 tional more ventral group of fibers. These subdivisions, ordinarily 

 lumped together in descriptions, seem to possess a fair degree of 

 constancy in a number of insect orders, and may be of significance in 

 future more detailed comparative studies. 



The fact that the furcabdominal muscles are inserted on the second 

 (never on the first) abdominal sternum, is what would be expected 

 if the furcal attachment is really intersegmental, as has been argued 

 above. Morphologically, these muscles still run from the third 

 thoracic intersegment to the first abdominal intersegment, and have 

 neither lost nor shifted their original attachment sites. However, just 

 as the muscle 2sps-SjiA has become 2sps-SiuA in some species (sec- 

 tion i,e), so is a portion of jus-sha found, at times, as fus- 

 siiiA, as a result of an analogous development (figs, i, 5, 8, 11, 12, 



