Val Bourne Wildlife
Val looks at the relationship between bees and pollen
I’M one of those people who snuffles through late spring and early summer, because I suffer from a pollen allergy. I think it’s probably tree pollen, and lots of early flowering trees disperse fine dust-like pollen on the wind. Most plants aren’t wind pollinated. They produce larger, sticky pollen grains designed to stick to creatures visiting the flowers.
However, some plants hedge their bets and show ambophily, which means they are both wind and insect pollinated. European willows, including the white willow (Salix alba), are primarily insect pollinated, but pollen can also travel on the wind if the weather conditions demand it.
The name of the game is to transfer pollen from the male anthers of one flower to the female stigma of another, so that cross-pollination occurs. Every pollen grain is unique to that plant, so they need to land on the correct stigma to create magic. This is why pollinators are so important, because most plants need a go-between to carry pollen from one flower to another. This transfer of genetic material needs to happen if seeds or fruit are to be produced.
I spend a lot of time trying to see where the pollen is on my bees. It’s easy with honey bees, because they have two pollen baskets halfway up their back legs. These ‘bees’ knees’ contain a mixture of pollen and nectar. Once the pollen and nectar mixture is packed into the honey bee’s basket, it cannot aid further pollination. Pollen rarely sticks to honey bees, because they have smooth bodies, probably because they are thought to have originated in eastern tropical Africa. They only fly when the weather’s clement and they are systematic pollinators. They visit the same sort of flower until the nectar and pollen sources are exhausted.
Hairy-bodied bees, such as bumblebees, almost certainly originated in cooler climates because they have furry bodies to keep them warm. This allows them to fly in lower temperatures than honey bees, and I’ve seen queen bees out in very low temperatures. Conversely, they do not enjoy extreme heat, because of their hairy coats. They all but disappeared from my garden in the hot summer of 2018, only returning once it cooled off in autumn. Then they carried on foraging until November.
Bumblebees browse and visit many different types of flower as they forage for nectar and pollen. The females and queens carry pollen on their legs, which have a series of combs and brushes. They brush the pollen into their baskets on the underside of their back legs, but these baskets can be quite hard to see. They also store nectar in their abdomens and can carry up to 31% of their body weight in pollen and nectar. Pollen often sticks to their hairy bodies and they can transfer pollen unintentionally.
Certain bees have hairy undersides, almost like a woolly carpet, and they are the best bee pollinators. When they arrive at a flower, they transfer pollen from their undersides. The leaf-cutter bees (Megachile species), the mining bees (Andrena species), the common carder bee (Bombus pascuorum) and mason bees (Osmia species) have no need of pollen sacs or baskets. It’s carried on their undercarriage, and this makes them very effective pollinators.
There’s one group of bees that don’t collect pollen at all, as they just feast on nectar when they need to. These are cuckoo bees that are intent on laying their eggs in bumblebee nests. They leave the workers of the nest to rear their young. The cuckoo females emerge from hibernation much later than ordinary bumblebee queens, so there will already be established nests to prey on. You’ll find them all in your garden.
“The name of the game is to transfer pollen”