Bumblebees as pollinators
Click links for specific crops)
Bumblebees are the superstars of pollination, bee for bee they are generally far better pollinators than honeybees. Pollination is the transfer of viable pollen (the male gamete) from the male parts of a flower to the female parts of a flower, which can then fertilise the ovary (the female gamete) and produce a seed. Bumblebees are incredibly efficient pollinators of many commercially grown plants, as their large size and hairy body allows for the extremely effective collection and deposition of large quantities of pollen. The more pollen transferred the better, and effective pollination increases the fruit quality (number of seeds developed, improving fruit size, weight and shape), as well as the quantity (percentage of fruit set, overall number of fruit), and can be the difference between a bountiful or meagre crop.
Bumblebees visit flowers to collect pollen as food for their young, and in doing so, provide pollination services to the plants (a mutualistic relationship). When a bumblebee flies it creates an electrostatic charge across its body. During a flower visit the pollen from the anther (part of a plant’s male organ) is electrostatically attracted to the hairs on the bumblebees body, which it picks up through contact with the anthers. When it moves from flower to flower, some of the pollen is rubbed off of the bumblebee and onto the stigma (part of the plant’s female organ). This normally happens through direct contact, but the now statically charged pollen may also jump short distances to the stigma, which is well grounded.
Bumblebees perform buzz pollination
, also known as sonication, an efficient means to extract pollen.
Bumblebees are not constrained by the same sort of weather conditions that honeybees are. Bumblebees will fly at temperatures above or around 5˚C, which is 10 degrees lower than honeybees, who generally require temperatures to be above 15˚C. Bumblebees will also forage on windy, low-light and overcast days, or during light drizzle, when honeybees stay at home. The larger size of the bumblebee enables them to manipulate flowers more efficiently, which means that they generally spend less time on the flower (while providing more effective pollination), and can service more flowers per hour. So, a bumblebee will start foraging earlier and stay out for longer than a honeybee, forage on days when the weather is less than ideal, and is more efficient while doing it! This means that fewer bumblebees are required to pollinate a crop than honeybees, which is a good thing when you consider that a large bumblebee hive might be 200 individuals, whereas a honeybee hive is more like 30,000!
Icons sourced from the Noun Project, click here to see acknowledgements.