Studies on the neurosecretory system of three aquatic beetles: Hydrus indicus, Cybister limbatus and Sandrocottus dejeani (Coleoptera).

Neurosecretory cells have been observed in the brain, suboesophageal ganglion and all the ganglia of the ventral nerve cord of three aquatic beetles - Hydrus indicus, Cybister limbatus and Sandrocottus dejeani. In the pars intercerebralis, neurosecretory cells are fewer and smaller in comparison to those in other locations in the brain. In other ganglia the number of neurosecretory cells is always larger than in the brain. Neurosecretory cells in the terminal abdominal ganglion of Sandrocottus are especially large. These may be concerned with some special function. On the basis of their tinctorial properties neurosecretory cells could not be differentiated into types.