18.104.22.168. Displaying the alimentary canal (Plate 9)
1. Take a needle in each hand.
2. Pass them under the rectum and ventriculus
3. Lift up the alimentary canal, gently tearing away the network of investing tracheae in which it hangs.
4. Lay it over to the left side, as shown in Plate 9.
5. Carefully tease out the tracheae and Malpighian tubules to permit the canal to lie loosely, showing all its parts.
6. Identify and examine the parts. Notice:
6.1. the six rectal pads, which appear as whitish bars on the wall of the rectum;
6.2. the small intestine, as a narrow coiled tube with six longitudinal pleats;
6.3. at its junction with the ventriculus, about one hundred Malpighian tubules are inserted. This is the pyloric region of the canal;
6.4. the ventriculus, in which food masses in the course of digestion can usually be seen, showing as dark areas where the corrugations of the ventriculus are smoothed out. If the ventriculus is torn with a needle, this food mass will exude as a brownish gelatinous substance.
6.5. the proventriculus, which will be visible through the walls of the crop if it is full of nectar. In any case, tear open the wall of the crop, using needles, and turn up the proventriculus so that its four triangular lips may be clearly seen. If they are closed, the lips meet to form a cross. If they are partly open, an aperture like a four pointed star is seen;
6.6. the forward end of the crop, which narrows into
6.7. the oesophagus, which enters the thorax through the petiole.