ANATOMY AND PHYSIOLOGY 



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small ingrowths, occurring sometimes in all three thoracic segments, 

 though usually absent in the prothorax. The furcae occur in each 

 thoracic segment as a pair of conspicuous processes, which either 

 remain separate or else unite more or less; leaving, however, a passage 

 for the ventral nerve cord. 



FIG. 60. Ventral aspect of a carabid beetle, Galerita janus. I, prosternum; 2, proepi- 

 sternum; 3, proepimeron; 4, coxal cavity; 5, inflexed side of pronotum; 6, mesosternum ; 7, 

 mesoepisternum; 8, mesoepimeron ; 9, metasternum; 10, antecoxal piece; 11, metaepi- 

 sternum; 12, metaepimeron; 13, inflexed side of elytron; a, sternum of an abdominal seg- 

 ment; an, antenna; c, coxa; /, femur; Ip, labial palpus; md, mandible; mp, maxillary pal- 

 pus; t, trochanter; lb, tibia; ts, tarsus. 



These endoskeletal processes serve chiefly for the origin of muscles 

 concerned with the wings or legs, and are absent in such wingless forms 

 as Thysanura, Pediculidae and Mallophaga. 



Some ambiguity attends the use of these terms. Thus some writers 



