56 



THE ANATOMY OP THE HONEY BEE. 



the general surface and mostly concealed between the naesothorax 

 and the metathorax. In higher families such as the Pompilidse the 

 postnotum of the mesotergum is entirely concealed by invagination, 

 but it still carries a very large, phragma. When, now, we come to 

 the highest members of the order we find that the median part of the 

 postnotum in the mesothorax is gone entirely and that it is repre- 

 sented only by the lateral arms (figs. 22, PN ; 23 A, PNo) carrying 

 the large, purely internal postphragma (Pph). 



The mesopleurum is large and consists principally of the episternum 

 (fig. 21, EpSo), which, however, is continuously fused with the meso- 

 sternum (figs. 20 and 21, 82)- The pleural suture (fig. 21, PS^) is 

 short and sinuous and does not reach more than half way from the 

 wing process to the base of the middle leg. The epimerum is reduced 

 to a small double plate lying above the episternum and posterior to 

 the wing process (figs. 21, Epm., and 24 A, Epm and Epm). The 



pleural ridge (fig. 24 B, PR) 

 is weak, but the wing process 

 (WP) is well braced by a num- 

 ber of accessory internal ridges. 

 One preparapterum {2P) and 

 one postparapterum {3P) are 

 present. Lying behind the 

 postparapterum is another 

 larger sclerite (fig. 24 A and 

 B, pn), whose anterior end is 

 articulated to the edge of the 

 epimerum and whose posterior 

 tapering end is loosely asso- 

 ciated with the terminal arms 

 of the postnotum (fig. 22, PN and pn). This sclerite might be 

 regarded as the fourth parapterum, but it is much more probably 

 the representative of a small terminal bar of the postnotum present in 

 other Hymenoptera, such as Pepsis, which connects this tergal plate 

 with the epimerum, though in this genus it is not detached from the 

 main postnotal sclerite. 



Both the mesostermim (fig. 20, S.^) and the metasternum (S^) con- 

 tribute to the formation of a large entosternum (T^Wj+g), which forms 

 a protecting bridge over the combined mesothoracic and metathoracic 

 ganglia (fig. 52) and affords attachment for the»ventral longitudinal 

 muscles of the thorax (fig. 27, Imcl). 



The metathorax consists of a very narrow series of plates (fig. 21, 

 7*3, PZg, and pl^) compressed between the mesothorax and the first 

 abdominal tergum {IT) . Its back plate is a single, narrow, transverse 

 sclerite (figs. 21 and 23 A, T^) widening on the sides, where it carries 

 the wings by the two wing processes' (fig. 23 A, ANP and PNP) . The 



Fig. 22. — Lateral view of mesotergum of 

 worker, removed from the rest of thorax to 

 show large internal postscutellum (post- 

 notum, PX) and its phragma {Pph) not 

 visible normally in the bee from exterior. 



