How to use Heidenhains azan staining in insects

A newly modified, histochemical Azan staining procedure which was originally designed by Heidenhain was adapted for insects. This led to new insights in the structure of the central nervous system of flies. The somata are weakly stained with a red colored nucleus. Neuroglial regions are stained intensively red. Some undefined portions of the neuronal tracts seem to be uncolored but the unstained profiles are still visible. The other portions contain blue colored cells. These differences may be due to the cells' different monoamine content. Using this method new morphological substructures could be identified in both the mushroom bodies and the central complex of the central nervous system that do not seem to be described earlier.