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ENTEMAN. 



[Vol. II. 



?«., points of attachment for mus- 

 cles ; s., support of nerve cord. 



The accompanying schematic figure after Graber will serve 

 to give an idea of their usual form and function, x represents 

 the apodeme in cross-section between 

 two successive thoracic segments ; in, 

 points for the attachment of muscles ; 

 Sy support for the nerve chain. 



These structures reach their highest 

 development and are most conspicuous 

 where the power of flight is strongest, 

 or locomotion is confined to only a few 



appendages. But we find a distinct Fig.i. -Transverse section through 



. . the thorax of an insect. (Sche- 



beginning for them m the myriapods, matic after Graber.) .r., apodeme; 



where each body segment is provided 



with a pair of appendages. In Scolo- 



pejidra (Fig. 3), for example, the intersegmental fold deepens 



toward the median line of the 

 ventral body wall, and here we 

 find attached two pairs of mus- 

 cles. This intersegmental deep- 

 ening is relatively uniform, with 

 the exception of the first five 

 segments of the body, where it 

 is shallower to correspond with 

 the slighter development of the 

 legs. 



The accompanying figure of 

 an ant, Myrmica rubi'a, shows 

 the extent to which the devel- 

 opment of the apodemes may 

 be carried in a highly specialized 

 insect. It represents a sagittal 

 section through segments three 

 to seven with the apodemes, to 

 which the ventral longitudinal 

 {m.v.vi.) and the ventral lateral 

 anterior muscles {m.v.vi) are 

 attached. The dotted line rep- 

 resents the nerve cord. 



Fig. 2. — Sagittal section through Myrmica 

 rubra. (After Janet.) «/., apodemes ; ^.-3-5, 

 ganglia ; m.c.x.^'^, muscles of coxae ; m.v.a., 

 anterior ventro-lateral muscles; m.v.ju., 

 longitudinal ventral muscle ; ;«.</.;//., dorsal 

 longitudinal muscle ; m.d.a., anterior dorso- 

 lateral muscle; ni.d.p., posterior dorso- 

 lateral muscle. 



