110 



THE ANATOMY OF THE HONEY BEE. 



coniniuiiicate willi (lie ooneral cavity of the abdomen only through 

 the ventral sinus. 



The dorsal diaphraoni (fig;, 1, DDph) ends by a free transverse 

 edge near the front of the third abdominal segment. A part of it is 

 shown by figure 47 extending aci'oss our segment and the adjoining 

 parts of two others. The fan-shaped bunches of muscle fibers 

 (Dp/uVcJ) are seen radiating from the anterior edges of the terga 

 toward the midline, where they are mostly continuous with those 

 from the opposite side, only a few^ of the anterior and posterior ones 

 ending free in the membrane of the diai)hragm. The latter is imper- 

 forate, but its edges are deeply scalloped between the points where 

 the muscles are attached, allowing free entrance to the blood from 

 the intervisceral channels of the abdomen. The dorsal surface of 

 the diaphragm is covered by a network of cells (figs. 47 and 48,. 

 DphCls) arranged in flat branching and fusing bands. These cells 



PphMcI 



Fig. 48. — Small part of dorsal diaphragm of drone, showing bands of flat diaphragm cells 

 (DphCls), the diaphragm membrane itself {Dphnib), and the muscle fibers (DphMcl). 



may be called the dlaphrarjm cells to distinguish them from the 

 pericardial celjs to be described later. 



The abdominal circulation is very easy to observe in a living 

 bee. The best way to demonstrate it is to pin an asphyxiated bee 

 to a block of cork or paraffin and remove the top of the abdomen 

 by making an incision with a small pair of scissors clear around it. 

 Gently pull the alimentar}^ canal to one side so as to expose the 

 ventral diaphragm, which Avill be observed pulsating strongly back- 

 ward. Xext cut a small hole in the top of the thorax and insert 

 into it a drop of some stain in a water solution (the Avriter used 

 carmalum). Almost immediately this will appear in the ventral 

 sinus of the abdomen, in Avhich it is pump(Ml backward by the dia- 

 phragm, and from which it goes ui)ward through invisil)le channels 

 between the air sacs aiid the alimentary canal and especially up 



