With the explosion of interest in bees, it's no surprise that more questions are being raised, and long held assumptions are being challenged. One of those questions is: "Are bees vegetarian?".
Fortunately, the ever increasing volume of questions is quite possibly being matched by scientific output aimed at answering them, and expanding our knowledge of probably the world's most studied living creature after humankind.
So here's what we know so far about bees and their diets.
For as long as I can remember, it was an assumption held by most people that bees are vegetarians. However, exceptions to the rule have been long identified. It may even be argued that bees are, in fact, omnivores.
It is known that when rebel workers in honey bee colonies lay eggs, those eggs are eaten by fellow workers1 to help ensure only eggs laid by the queen will survive.
Cannibalism in honey bees has also been recorded: adult workers may consume their own larvae during times of pollen shortage2 and to control brood rearing ratios in a colony, for example, by eating more drones than workers3.
It could therefore be argued that honey bees are not strictly vegetarian, even though their main diet is nectar and pollen.
In 1990, another paper was published4 which documented bumble bees feeding from the rotting carcass of a wild goat (as well as bird and coyote droppings) in Spain.
Again, whilst bumble bees are known to live primarily on a nectar and pollen diet, it was proposed that certain environments gave rise to this particular foraging behaviour, in order for those bumble bees to fulfill their nutritional requirements that were otherwise unavailable.
There are bee species such as the Vulture bees of the genus Trigona, found in tropical locations that are known to be meat eaters, and not vegetarian.
Trigona were the subject of a scientific paper published in 19825. The behavior of vulture bees (observed, for example, to feed on dead lizard and chicken) left no doubt that these bees are indeed meat-eaters, and not vegetarians.
UCR entomology student, Jessica Maccaro, observes vulture bees feeding on chicken.
The plot thickens!
If it seems from the above examples that most bees are purely vegetarian, but resort to cannibalism as a survival strategy, there is yet again scientific evidence to challenge such a view.
Scientists at the Department of Entomology, University of Wisconsin–Madison, argue that pollen contains many microbial communities, all feeding on the pollen which in turn is enhanced by the microbes, and consumed by bee larvae. The authors of the study (Steffan et al6) argue that the pollen-eating microbes are functionally herbivores.
Therefore, when bees in turn consume the microbe-rich pollen, they are, in effect not only eating plant protein, they are also eating protein-rich herbivores along with the pollen! Thus Steffan et al argue that the eating of pollen by bees means that bees are in fact, omnivores.
1. Rojek, W., Kuszewska, K., Ostap-Chęć, M. et al. Do rebel workers in the honeybee Apis mellifera avoid worker policing?. Apidologie 50, 821–832 (2019). https://doi.org/10.1007/s13592-019-00689-6.
2. Schmickl, .T., Crailsheim, .K. Cannibalism and early capping: strategy of honeybee colonies in times of experimental pollen shortages. J Comp Physiol A 187, 541–547 (2001). https://doi.org/10.1007/s003590100226
3. Woyke, J. Cannibalism and brood-rearing efficiency in the honeybee. J. Apic. Res. 16, 84–94 (1977).
4. Carlos M Herrera (1990) Bumble Bees Feeding on Non-Plant Food Sources, Bee World, 71:2, 67-69, DOI: 10.1080/0005772X.1990.11099039.
5. Roubik DW. Obligate necrophagy in a social bee. Science. 1982 Sep 10;217(4564):1059-60. doi: 10.1126/science.217.4564.1059. PMID: 17839343.
6. Omnivory in Bees: Elevated Trophic Positions among All Major Bee Families. Shawn A. Steffan, Prarthana S. Dharampal, Bryan N. Danforth, Hannah R. Gaines-Day, Yuko Takizawa, and Yoshito Chikaraishi. The American Naturalist 2019 194:3, 414-421