Welcome to my NBoNA blog, today is about bumble bees (Bombus spp.)!
In the United States and Canada, we have more than 40 different species of bumble bees, all falling into the genus Bombus. They share a family (Apidae) with honey bees (Apis mellifera) and carpenter bees (Xylocopa spp.).
NB: The notation "Genus spp." is used when referring to a group, but not any one species in particular, and often when there are multiple species present. On the contrary, the "Genus sp." notation is used when there is certainly only one species present (in a photograph, for instance), however the species cannot be determined.
Our Bombus spp. come in a variety of colorations, patterns, and lifestyles. From the ubiquitous in the east B. impatiens (above), to the critically endangered B. affinis, otherwise known as the Rusty-patched bumble bee (below). From nesting underground in rodent burrows, to claiming a tree hollow. From typical eusocial nest building behavior, to parasitic, nest usurping cuckoo bumble bees.
Bombus affinis f, Photo Kim Mitchell; USFWS
Bumble bees are quite similar to the familiar honey bees, given they both choose to have a singular queen laying eggs, and workers to help provide for the nest. This is what we call "eusocial" behavior, which is also a common strategy for ants, who are fellow Hymenopterans. A nesting hierarchy such as this allows for much more efficient collection and distribution of resources, however honey bees have taken this to the extreme. Our insistence on farming these bees leads to them achieving colony sizes that can near 100,000 individuals, whereas Bombus in extreme scenarios may achieve 400-500 individuals. Keeping up such a large amount of biomass alive takes quite a lot of energy (namely: sugar). Basic biology tells us that the larger bumble bees have a smaller surface area to volume ratio, which leads to more efficient use of energy and less heat loss. This is the very reason why you might see bumble bees active far earlier and far later than many other insects are, they are a good example of quality over quantity.
So why are honey bees bad, and bumble bees good? (generally speaking)
It all comes down to one thing: pollination. Well, honey bees are quite industrious to begin with, but we have helped accentuate that with our efforts to farm them for centuries. Compare this to the bumble bees that have lived here for a few million years, and you might start to grasp why the native plants here would prefer the more experienced bumble bees to pollinate them. Compounding with this is the fact that honey bees are often so good at collecting pollen, they are bad pollinators.
The system works like this: a flower will offer a nectar reward, which will attract a bee, or any other nectar drinking animal, to feed. The flower's pollen structures will be located in a spot where the feeding animal has to make contact with them. This is the basic trade that goes down, albeit the pollinator usually is not pollinating on purpose, it just kind of happens. We call this incidental pollination and it extends into some wasp, beetles, birds, and even bats! When the pollinator then makes its way over to the next flower, some of this deposited pollen will hopefully shake off and onto the pollen structure of the new flower. As this repeats, the pollinator is building up a mix of pollen, in other words has diverse genetic material for the plants to use.
Now, this could present a problem, if there are many different species of flower visited, the genetic material deposited each time has a high likelihood of being incompatible. What bumble bees (and honey bees) do to alleviate this is display a remarkable amount of flower constancy, or showing high preference for one species of flower on a given foraging trip. This has actually been shown in honey bee hives as a way for the bees to make certain monofloral honeys, which may have different medicinal benefits depending on the flower!
If you are in the US or Canada, then at the moment you can probably go out to see many Bombus queens out searching for nesting locations, or foraging for their first brood!
Bombus bimaculatus q
It starts in the spring, when hibernating queens will be waking up to begin their search for a nesting site. They will specifically search out smells similar to lemongrass oil, which is an indicator of rodent urine being present. She does this, because rodent burrows are often the perfect size and easily concealable, making for a perfect nest. Like I said before though, there are some species that like to nest either directly on top of the ground or a few feet above ground, this is a general overview! Once she has found a suitable nesting location she will lay her first brood of eggs, often a smaller clutch than normal, because it is easier to care for a few workers. Having just a few, larger workers to start is less risky than spreading too thin, which could lead to the entire nest failing. In order to hold the young bees, she will use pollen and some of her saliva to make a bunch of cups which house the young and used as nectar storage. With eggs laid, she will go off foraging, to keep herself going and also to bring back provisions for her young brood. This will go on for the week or so it takes for these initial workers to develop. After this first brood is hatched and pupated, the queen will no longer leave the nest, retired to a season of laying eggs. From here on out, the workers will handle all foraging, nest building, and care for the new brood.
Later in the summer, some eggs laid will be unfertilized, which in the bee world means that will hatch a male (genetic stuff that we will get into later on). Drones will begin to be born, and some females will be designated daughter queens, being fed much more than the others. Once these reproductive parts of the colony emerge, they immediately leave the nest. The goal is to find a mate from a colony that is not your own, after which the males die off and daughter queens survive the fall and hibernate for the winter. Spring comes and the cycle can repeat itself once again!