220.127.116.11. The underlying organs (Plate 10)
1. Grasp the alimentary canal with forceps.
2. Stretch it.
3. Cut through the oesophagus with scissors.
4. Treat the rectum in the same way, cutting through it as far back as possible.
5. Carefully cut away the remaining small triangle of the roof which was left at the tip of the abdomen.
6. Lower the side walls with scissors, giving a better view of the floor.
7. Flush out the cavity with the pipette.
8. Compare with Plate 10.
9. Identify and examine the parts. Notice:
9.1. the ventral diaphragm, which may not be noticed at first, but closer inspection will reveal it as a transparent film which very slightly obscures the view of the chain of ganglia and other underlying features. In a later dissection, the diaphragm may be studied more carefully; it is attached to the apodemes of the sternites; its anterior end extends into the thorax and is attached to the furca of T2 and T3, while its posterior end is anchored to the spiracle plate of A8.
10. Tear out the diaphragm with the fine forceps, taking care not to damage other structures in the process.
11. Observe the now more clearly visible organs lying on the floor of the abdomen:
11.1. the chain of five ganglia is the most conspicuous, it is connected by twin longitudinal commissures. The last, the 7th ganglion, is attached to the sting apparatus, and comes away with the latter when it is torn out of the worker's body after stinging;
11.2. the main lateral nerves which spring from the ganglia can be seen running out to right and left; those of the 7th may be seen passing to the muscles of the sting;
11.3. the fat body spreads widely over the floor of the abdomen, being particularly well developed over the wax glands of the sternites of A4 to A7. Smaller clusters of fat cells occur along the sides of the abdomen. The fat body is highly developed in young bees and winter bees, where the cells are large and plump, but in old foragers they are shrunken;
11.4. the abdominal muscles show clearly, some of the larger sets being very conspicuous as broad V-shaped pairs of bands stretching between the thickened forward margins of adjacent sternites;
11.5. the ovaries are difficult to see, and since they encircle the alimentary canal they are torn away when it is lifted out. To prevent this, after removing the roof of the abdomen,
11.5.1. lift the alimentary canal slightly from the right-hand side,
11.5.2. look sideways under it, the right ovary with its oviduct will be seen as an almost transparent, narrow, flat tube running to the root of the sting,
11.5.3. gently disengage the ovary from the tracheae which tie it down and attach it to the other viscera,
11.5.4. repeat this operation from the other side, thus freeing the left ovary,
11.5.5. go on with the dissection, removing the canal.
The ovaries will then be seen lying or floating in the abdominal cavity, their oviducts disappearing behind the sting, their distal ends separated. In the undisturbed abdomen, the tips of the ovaries are joined and attached to the heart (Plate 17).
11.6. the sting, if not wholly visible, can be examined in situ by removing more of the wall of the abdomen at the tip (Plate 10). Identify the parts flagged in Plate 11, dorsal aspect. The whole apparatus can be removed intact very easily by passing needles below it and lifting it out, the small muscles which hold it giving way without offering noticeable resistance. The extracted apparatus can now be turned over, as it lies in clear fluid, and its ventral aspect (Plate 11) can be examined. Very rarely, the sting apparatus is laterally reversed, the only evidence of this being that the positions of the venom gland and the alkaline gland are reversed. The powerful muscles of the sting apparatus conceal the plates which constitute the system of levers actuating the lancets. The plates can be exposed by removing the muscles by maceration. Note that the sting apparatus is arched; it can be flattened by tearing away the proctiger, which is firmly attached to the oblong plates, and it is then easier to examine and also to mount as a microscopical preparation.