Buzzy Bee Garden Behaviors
by Jaime Pawelek
Nectar Robbing. Have you ever seen holes in the base of your flowers, especially the long tubular ones? They are the result of what is called “nectar robbing”, which is done by many different pollinators like bees, birds, ants, and moths in various parts of the world. In the case of bees, they go straight to the nectar reward, bypassing the sexually reproductive parts, and cut holes in the base of the corolla to suck out deliciously sweet nectar. In California, we often see bees with short tongues, like carpenter bees and bumble bees, doing the initial nectar robbing. Bees that make the first hole are called primary nectar robbers. There are also secondary robbers, like honey bees, other bumble bees, and moths, which visit the flowers and use the pre-made holes to secure the nectar (reward).
Bees make holes by poking the flower with their proboscis or by biting it with their mandibles. Another method of nectar robbing occurs when the “robber” inserts its tongue (proboscis) between the sepal and petal of the flower to gain access to the nectar. They usually nectar rob when their tongues are too short for the long flowers and have no other way of getting the nectar.
When bees nectar rob from a flower, pollination doesn’t always occur. Some robbing bees will inadvertently touch the pollen and carry it on them to the next flower, but this is not always the case. Lack of pollination from nectar robbing can lead to fewer seeds and fruits being produced. Alternatively, the legitimate pollinators may seek out more flowers to fill their nectar needs because of the diminished nectar reward left by the robbers. This increased flower visitation may actually increase seed set and genetic diversity. Some of the California flowers that experience nectar robbing include Autumn Sage (Salvia greggii), ‘Hot Lips’ Sage (Salvia ‘Hot Lips’), columbines (Aquilegia spp.), and California fuchsia (Epilobium canum).
One plant in particular that is regularly robbed in California is bog sage (Salvia uliginosa). Carpenter bees make their holes in the base of the flowers, which are then used commonly by bumble bees and honey bees. None of these bees actually pollinates the flowers; instead, they are pollinated by much smaller sweat bees (Halictus spp.). These tiny bees gather pollen from the end of the flower’s reproductive parts and make their way from flower to flower. It’s interesting to see this interaction take place because one tends to focus initially on the larger bee, but with closer observation it becomes clear that the large bees are robbing and the tiny bees are actually pollinating the flowers.
Bee Sleepover. Have you ever wondered where bees go to sleep at night? If you take a look in your garden early in the morning you will see some species sleeping right on the flowers! Male bees don’t have a nest to go home to, so some find a cozy flower to rest on. In our California garden we commonly see aggregations of long-horned bees (Melissodes spp.) having a sleepover in the flowers. In the case of Cosmos bipinnatus and sneezeweed (Helenium puberulum), we see up to 15 of them sleeping on one flower head! We have also seen the lone bumble bee latched onto flowers like bog sage (Salvia uliginosa) and sea daisy (Erigeron glaucus).
Bees hold on with either their legs or their mandibles and tuck in for the night. Some of the flowers we see them on are sneezeweed (Helenium puberulum), Mexican aster (Cosmos bipinnatus), and bush sunflower (Encelia californica). They also sleep in flowers that close up for the night, like CA poppy (Eschscholzia californica), which probably keeps them safe from predators. As soon as the day starts to warm up the bees will begin stirring and again begin their search for females to mate with.
Male squash bees look like they’re sleeping in the open squash blossoms (and in the mid mornings when the flowers close they are), but they are actually waiting for the female bee to visit the flower so they can mate. If you want to know if you have squash bees in your garden, and don’t want to get up before dawn to see them, try pinching some of the closed squash flowers after mid morning. If you get a buzz from the flower that means a male squash bee is resting in the blossom, and then you’ll know that females are in your garden doing their job pollinating your squash.
The chase is on! Many male bees are territorial and patrol an area around a patch of flowers in search of un-mated females. For them to be successful in mating they often chase off rogue males that enter into their territory. If you observe a patch of attractive flowers, like Cosmos bipinnatus, you can easily see these interactions first hand. You’ll see some bees flying really fast, not landing very often or at all. These are males chasing each other around in hopes to be the first one to mate with a female. The females actively visit flowers in search of nectar and pollen. The males only stop briefly to re-energize with a sip of sugar-rich nectar.
One of the most territorial and aggressive bees is a wool carder bee (Anthidium spp.), which we have nicknamed the head-bonker bee! This male bee chases off all other bees from its’ territory in order to attract a female. We have seen them attack honey bees, bumble bees, and even the large carpenter bees! Most times the bee just “bonks” into another bee knocking it off the flower, sometimes discouraging it from foraging there any longer. These carder bees do have spikes at the tip of their abdomen that they use when fighting other bees and have even been known to kill honey bees. The head-bonker may also attempt to chase people away from their territory, hence the name “head-bonker”. Not to worry though, male bees can’t sting; he’s just using his aggressive behavior to scare you away.
These chasing males are fun to watch, and it’s interesting to note that these are the same ones sleeping in the flowers together! After a long day of chasing each other around, they settle down and sleep curled up next to each other on a flower head. What strange bedfellows!