NO. 2 HONEY BEE — SNODGRASS 33 



represent a cervical sclerite fused with the pleuron. On the lower 

 posterior angle of the pleural plate is articulated the coxa of the first 

 leg (C, Cx). From the coxal articulation there extends upward close 

 to the posterior pleural margin a groove (pis), which is the pleural 

 sulcus, since it runs into the base of the large internal pleural 

 apophysis {PI A). The groove sets off a very narrow posterior 

 epimeral strip (Epm) of the pleuron from a large anterior episternal 

 region (Eps). 



Internally the episternum presents close to its upper margin a wide, 

 shelf like horizontal apodeme (fig. ii E, c) inflected from a sub- 

 marginal groove on its outer surface (C, b). The horizontal apodeme 

 expands anteriorly into a large mesal lobe (C, E, d), termed by 

 Duncan (1939) in the wasp the "posterior ramus of the occipital 

 process," but which, since it gives attachment to several muscles that 

 are in most insects inserted on a distinct neck sclerite, may ap- 

 propriately be named the cervical apodeme. The cervical apodeme and 

 the pleural apophysis form prominent points of muscle attachments 

 at opposite ends of the pleuron. 



The prosternum lies ventrally between the pleural plates and the 

 bases of the coxae (fig. 11 G). It is differentiated by a narrow 

 constriction into a wide, triangular, anterior basisternal region (Bs) 

 flanked by the episterna, and a narrow, elongate, posterior fiircasternal 

 region {Fs) lying between the coxae. The furcasternum bends up- 

 ward at a steep angle from the horizontal basisternum (I), and carries 

 an elaborate endoskeletal structure, the prothoracic cndosternum. 

 Externally the furcasternum is featured by a median groove (K, /), 

 and by a pair of posterior pits {g) that mark the roots of the sternal 

 apophyses. 



The prothoracic endosternum. — The large endoskeletal structure 

 supported on the sternum of the prothorax occupies much of the in- 

 terior of the segment (fig. ii B, E, Endst) and gives attachment to 

 various muscles (fig. 12 B, C). Structurally the endosternum includes 

 a supporting base on the furcasternum, a pair of laterally divergent 

 dorsal wings, and a horizontal bridge between the wings. The sternal 

 support consists of a vertical median plate (fig. ill, h) inflected 

 from the median groove of the furcasternum, which posteriorly is 

 reinforced by a pair of lateral thickenings (i) arising from the 

 posterior furcasternal pits, and anteriorly tapers into a low ridge that 

 runs out on the basisternum (;'). The endosternal wings are a pair of 

 plates with thickened anterior margins diverging from the basal ridge 

 (J, k, k) in a forward direction because of the upward slant of the 

 furcasternum in the natural position (I). The bridge is a wide. 



