Quoting Bee Safe
Bee Health Consulting for Agriculture in veterinary Medicine
SALT PREFERENCES IN SUMMER AND AUTUMN
The researchers offered different minerals in a feeding experiment and compared if foragers preferred their solutions to deionised water. They studied this for several minerals (sodium, calcium, potassium, magnesium, phosphorus and nitrogen). For the effect of the season, they did the experiments in summer (July/August) and autumn (September/October). Interestingly, the water volume the bees collected did not depend on the season. Honey bees use water also for thermoregulation; therefore, requiring more water in the warmest months would have seemed reasonable. However, the preferrences for certain minerals did depend on the season.
Honey bee foragers preferred sodium (offered as NaCl, table salt) over deionised water independent of the season. The authors of the study explain this by the fact that above-ground parts of plants (i. e. also pollen) have very low contents. Therefore, the workers have to collect this micronutrients from other sources. This was the first confirmation for adaptive foraging, but it became even more interesting.
Preuss already in 1900 stated the preference for water enriched with table salt (i. e. sodium) compared to pure water. I do not have this last publication, but Kiechle cited him. Therefore, be careful in stating you are the first or second to examine something. You may just not know the publications because they are old or in another language.
References cited but not linked:
Goatley, J.L., Lewis, R.W. (1966) Composition of guttation fluid from rye, wheat and barley seedlings, Plant Physiology 41: 373-375
Kiechle, H. (1961) Die soziale Regulation der Wassersammelt?tigkeit im Bienenstaat und deren physiologische Grundlage. Zeitschrift f?r vergleichende Physiologie 45: 154-192