Another way of looking at foraging
It is still debated whether pollen-collecting insects, such as honey bees and bumblebees, maximize foraging efficiency by preferentially switching to protein-rich pollen. Choice experiments have shown that honey bees do not assess pollen protein content (Pernal and Currie, 2001, 2002). This is not surprising considering that protein is very rarely present in the pollenkitt, the oily layer coating the pollen grain, and free amino acids were not found in the pollenkitt of any of 69 plants studied (Dobson, 1988).
It appears that cues other than protein content affect bee pollen preferences. Such cues may include odors, phagostimulants and phagodeterrents (Schmidt, 1982), grain size (Pernal and Currie, 2002), and pollen concentration; honey bees dance more rigorously to a feeder containing a higher pollen-to-cellulose ratio (Waddington, 2001; Waddington et al., 1998).
Nectar is rich in sugars, but contains additional nutrients, including amino acids (AAs). We tested the preferences of free-flying foragers between 20 AAs at 0.1% w/w in sucrose solutions in an artificial meadow. We found consistent preferences amongst AAs, with essential AAs preferred over nonessential AAs.
It is unknown however, to what extent amino acid (AA) presence in nectar is valued, and further, if potential preferences are related to the nutritional state of the colony. Whereas pollen is the main source of AAs for bees, we cannot exclude the possibility that deficiencies in particular AAs in the colony may also modulate preference for nectars which contain those AAs.
Hendriksma, H. P., Oxman, K. L., & Shafir, S. (2014). Amino acid and carbohydrate tradeoffs by honey bee nectar foragers and their implications for plant–pollinator interactions. Journal of insect physiology, 69, 56-64.
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