As mentioned in this post, during late summer and fall in this area there is a relative dearth of nectar available for our honeybees, as they depend heavily on native forage.
One of the best native nectar sources this time of year for honey bees is Coyote Brush (Baccharis pilularis), but our plants seemed to bloom much earlier than normal this season, perhaps due to our drought, and are now simply a mass of seeds.
That has left the honey bees with few foraging options while they prepare their colonies for winter, and we’ve been squarely in the midst of a nectar dearth since June!
As would be expected at this time of year, the majority of our native wildflowers are dormant. We have a few Encelia californica in bloom, which aren’t a bad pollen source, although relatively low on nectar, and the bees don’t seem to spend much time near these flowers.
The most nectar-rich flowers in abundance on the farm at the moment are the California Fuchsias (Epilobium canum).
We maintain a few different cultivars of Epilobium on the farm, in part because they provide some welcome drifts of color on the slopes against the brown desiccated weeds and grasses at this time of year.
Typically, when people ask me about Epilobium, I mention that although the hummingbirds will happily forage among these flowers for nectar, they’re a poor nectar resource for our honey bees. The flowers are long, and tubular, and narrow toward the base, which makes it almost impossible for honey bees to exploit their nectar reserves.
Although the pollen is more readily accessible, as the pollen-bearing anthers of Epilobium are held beyond the petals, the honey bees don’t seem particularly interested in foraging for Epilobium pollen.
Even though Epilobiums produce nectar, honey bees are too large, and their tongues too short, to reach the nectary at the base of the flower. A problem for the bees, who have few nectar choices at the moment, but consider it from the flower’s perspective.
The Give and Take of Pollination
Nectar in flowers attracts insects, and provides a reward for those that forage on them. To reach the nectary, insects visiting these flowers typically have to brush past the pollen to reach the nectary, and the pollen grains are then transferred to other flowers as the insects move about. Pollinators, like bees, don’t pollinate flowers because they want to. Pollination is more incidental, than intentional, as bees and other insects travel from flower to flower in search of nectar as food.
Until yesterday, I haven’t really noticed honey bees giving our Epilobiums so much as a second thought. However, while photographing some native Goldenrod (Solidago californica) flowers this week, I noticed an absurd number of honey bees hovering around the Epilobiums, which seemed rather odd.
As I wasn’t expecting to see much honey bee activity in the vicinity of the Epilobiums, I watched more closely for a few minutes. I saw quite a few bees diving head first into the flowers, backing out, and flying on to the next one.
They were dragging pollen around, and pollinating the flowers, but it was questionable whether or not they were really succeeding in obtaining a nectar reward at all. Note that these bees clearly weren’t gathering pollen, as their pollen baskets were empty.
I could only assume that these bees knew the nectar was there, but had no idea how to reach it.
Engaging in Bad Bee-havior
Some of the bees clearly had figured out how to reach the nectar though. Following the bees between the flowers, a number of them were observed targeting the base of the flower, externally. Through a macro lens it became obvious that these bees were exploiting the nectar reserves through small cuts and slits at the base of the flower, which exposed the nectar.
Is Robbing Necessarily A Crime?
Pollination of flowers by bees is generally considered to be mutualistic. To successfully reproduce, flowers need to transfer pollen to another flower of its kind. For wind-pollinated, self-compatible flowers, this isn’t as much of an issue, but flowers that depend on insects for pollination encourage pollination by offering the insects a nectar reward. In this scenario, both the flower, and the pollinator, gain something from the exchange. The flower can successfully transfer its pollen to reproduce, and the pollinator receives food in exchange. It’s a mutually beneficial arrangement.
However, the shape of the flower may restrict the types of pollinators that can access the nectary to receive the reward. The nectaries in narrow, tubular-shaped flowers, like Epilobiums, are most easily accessed by small insects, or long-tongued bees (and long-tongued hummingbirds of course). Honey bees are quite large, and have short tongues, and are not well suited to pollinating these narrow, tubular, flowers.
These nectaries contained in the Epilobium flowers are essentially in a locked safe, and without the right combination (narrow body, and/or a long tongue), the nectar remains secured within that safe. However, some bees, like bumble bees, are masters at safe-cracking, and able to cut a hole in the side of these secure vaults just large enough to liberate the nectar within.
Although these honey bees were raiding these exposed nectaries, it’s not likely that they were the original vault robbers. When it comes to robbing nectaries, there are typically primary robbers, like bumble bees, that can chew holes into the petals to reach the nectar, and then secondary, opportunistic robbers, like the honey bees, that are simply looting the now opened vault, to exploit the treasure within.
As a result of this behavior the contract between flower, and pollinator, has been broken, as these bees are now stealing the ‘reward’, without providing pollination services in exchange.
However, at least half of the photographs I took of these honey bees among the Epilobiums show pollen-coated bees diving head first into the flowers. Pollen is still being transferred, albeit accidentally, from flower to flower.
Recent studies in bumble bees have shown that this type of robbing behavior may actually be learned, rather than innate. 
I’m not sure if the same is true of honey bees or not, however, watching these honey bees one could assume that those bees entering the flowers from the front might be new field workers from the colony, and that in an effort to reach the nectar, albeit unsuccessfully, perhaps they have not yet ‘learned’ how to reach the nectar at the opposite end of the flower.
Those that are successful in robbing the nectaries seemed to travel directly from one nectary to the next, they weren’t even bothering with the front of the flowers.
Others were clearly entering the flowers, and responsible for at least some degree of pollination occurring. Pollination efficiency is clearly not optimal, in that not all bees are entering the flowers from the front, but pollination is likely occurring nonetheless.
So although the robbing bees are cheating the system, some of them are moving pollen between the flowers without the benefit of a reward, perhaps reducing the level of the crime committed by these nectar-thieving honey bees to the level of a misdemeanor, instead of a felony. Besides, as the bumble bees were likely there first, these honey bees are merely an accessory to the original crime.
That said, there’s an element of risk to a honey bee that chooses a life of crime, especially at this time of year. While they’re busy robbing the Epilobiums of their nectar, squarely in the center of one large plant, I found a large female Banded Garden Spider (Argiope trifasciata), and one nectar robber that clearly didn’t make it back to the hive alive!
 Leadbeater, E., and Chittka, E. Social transmission of nectar-robbing behaviour in bumble-bees. Proc Biol Sci. 2008 July 22; 275(1643): 1669–1674.