A bumblebee has to open a snapdragon flower (Antirrhinum majus) to get inside. Antirrhinum flowers have five petals arranged into an upper and lower lip that develops a convex shape, called a palate, which effectively blocks the mouth of the flower tube. This type of flower is called ‘personate’, and because the lower lip is tucked in the upper one, it creates an effective barrier – i.e. between the nectar at the base of the flower tube – for any unwanted floral visitors (Vargas et al., 2017). In other words, the flower has evolved a relationship with the pollinator, only letting in those it wants!
The bee lands on the bottom lip of the flower, and its weight causes the flower to open so that the bee can crawl in.
The traditional scientific opinion, is that ‘strong bees’, albeit of different sizes, are the principal pollinators of such occluded, personate flowers and most other insects are not heavy or strong enough to open the corolla mouth (Guzman et al., 2015; Vargas et al., 2017). So, honey bees for example, are reportedly not able to open up the mouth of the flower; they are too small, or too weak! I did not see any honey bees trying to get into these snapdragons. They can get in however, if a bumble bee has cut a hole (a nectar robber) in the side of the snapdragon! But this did not happen in these snapdragons.
After the bee has entered the flower, it snaps shut again!
When the bee is finished extracting the nectar, it backs out!
Most of the bees I watched did not take very long to get the nectar and re-emerge backwards. They then flew on to another flower. Could they detect if the flower had recently been visited by another bee? I don’t know.
Some bees however, went inside a flower and stayed there! At first I thought that I had missed them coming out again, but when I opened a flower in which a bee had disappeared into, I found that the bee was still inside! What was it doing? Was it resting? Sleeping? Or just taking a nap! I will now look at snapdragon flowers differently; knowing that there might be a bee, asleep inside one!
In snapdragon flowers, the upper and lower lobes are apparently where the floral scents are emitted from. So to reach the nectar, the bees must move into the flower tube (or corolla).
When the bee brushes against the lobes of the flower, it picks up the flower’s scent, as well as the pollen it collects when it brushed against the stamens inside the flower (above). Some of the bees had pollen on their wings (below).
It’s probably worth pointing out that all of this activity was going on pretty quickly. I had to use a shutter speed of one 4,000ths of a sec to ‘freeze’ the bees sufficiently well. In some cases, even this was not fast enough. Shot with a 150mm macro lens.
Guzmán, B., Gómez, J. M., & Vargas, P. (2015). Bees and evolution of occluded corollas in snapdragons and relatives (Antirrhineae). Perspectives in Plant Ecology, Evolution and Systematics, 17(6), 467-475.
Vargas, P., Liberal, I., Ornosa, C., & Gómez, J. M. (2017). Flower specialisation: the occluded corolla of snapdragons (Antirrhinum) exhibits two pollinator niches of large long‐tongued bees. Plant Biology, 19(5), 787-797.