Flight of the bumblebee
Other bees may enjoy a sweeter reputation, but there are many reasons why the humble bumblebee is the true rock star of the insect pollinator world.
The super-pollinator in your garden
if ever there was a misnomer, it is the poorly understood bumblebee. This super-efficient pollinator has somehow become synonymous with anything inept, clumsy and ineffective. Yet, the bumblebee is anything but. With 50 times the pollinating power of honeybees, the humble Bombus is, in fact, a crucial link in the pollen chain and is fast becoming essential to some of our most lucrative horticultural producers.
The story of bumblebees in New Zealand started some 130 years ago, when they were introduced from England specifically to pollinate red clover ( Trifolium pratense), a popular pasture choice for new farms. Four species were imported: Bombus
terrestris, now the most common species in the country; Bombus ruderatus, living in most regions except Stewart Island; Bombus hortorum, found everywhere except north of Hamilton and Westland; and Bombus subterraneus, our rarest bumblebee, found only in inland Canterbury and central Otago.
Each species has distinct variations of black, yellow and orange markings.
Bombus terrestris, commonly called the large earth bumblebee, boasts a black waist with a broad yellow-orange band across its abdomen. Bombus ruderatus can range from almost completely black, to black with broad yellow waist colouring. Bombus hortorum has a yellow waist. Bombus subterraneus, also known as the short-haired bumblebee, has black hairs on the front yellow band.
Two features they all have in common are a long tongue (proboscis) to plunge into the throats of vertical flowers such as foxgloves or delphiniums, and the ability to buzz so vigorously they dislodge up to 50 times the amount of pollen that a honeybee can manage.
They’ve long been underestimated by the public, says New Zealand Bumblebee Conservation Trust’s (NZBCT) Geoff Brunsden, “because when observed they seem to just be going about their business quietly. But that business is very powerful, because one bumblebee will do the work of 50 honeybees.”
Not only that, bumblebees can work in conditions honeybees can’t. Bumblebees can work at temperatures just above freezing, in the rain and fog, from first light until dark. They can fly in covered areas such as glasshouses or within shrouded crops and they can pollinate up to 450 flowers per hour in such a space. “Their mission is to just get out there and work as many flowers as possible in the daylight hours,” says Geoff.
In fact, the hardworking insects are only ever 40 minutes from starvation due to the speed at which they travel (up to 54 kilometres an hour), and the strength required to carry their own weight plus up to 90 per cent of their body weight in food.
Along with their long tongues, the insects use “buzz pollination” or sonication, meaning they vibrate their bodies to cause pollen to be released, sometimes in a visible cloud. In this way, they gather more pollen than many other insects and create extremely effective cross-pollination as they move on to the next target while literally covered in pollen.
And if all else fails, these little power puffs have yet another clever tactic. For particularly deep-throated flowers such as broadbeans, they simply use their long proboscis to nip a hole in the base and go straight to the source of otherwise inaccessible nectar.
Yet for all the skills of the bumblebee, it is honeybees – with their hive numbers in the tens of thousands compared to the bumblebee’s more modest population of 400 per nest at the most – that are the rock stars of the pollinating insect world. This is probably because “honeybees contribute in an understood way to the economic wellbeing of people, whereas the bumblebee is just out there doing its job, and is not visibly bringing us a resource,” says Geoff.
Ironically, bumblebees work hard on many resources that we would notice the absence of, including the farmland plants they were first brought to the country to work on. “Bumblebees are essential to pollinate the introduced pasture plants that we rely on. Our animals graze on them, they nitrify the soils for grass to grow in, and so forth,” explains entomologist Dr Barry Donovan, who has studied them for over 40 years.
Hardworking bumblebees are only ever 40 minutes from starvation, due to the speed and strength required of them.
In terms of the fruit and vegetables, bumblebees are vital to the New Zealand tomato industry which has a farm gate value of $100 million a year, and the Bombus terrestris is bred commercially by several companies to be used in the indoor production of tomatoes.
Likewise, producers of indoor crops such as capsicum, eggplant, blueberry and courgette also frequently look to bumblebees to enhance their yield.
An emerging market is that of kiwifruit growers, who are increasingly looking to the bumblebee as an alternative to honeybees, which dislike working in the shrouded orchards and are steadily becoming more expensive. It’s also believed that bumblebees work the flower of the kiwifruit much more efficiently – nearly double the contact on the flowers’ stigma than the honeybee.
Waiuku-based bumblebee producer Zonda Beneficials has seen “huge growth” in outdoor covered crops such as kiwifruit and passionfruit which have traditionally relied on honeybees, according to sales and administration spokesperson Tracy Calder. “The varroa mite has caused issues [with honeybee usage], and the cost attributed to getting honeybee hives is getting quite high because a lot are being used predominantly for manuka honey production.”
Tracy says over the past four and a half years at Zonda, demand for bumblebee hives has outstripped supply. “Before, it was more the indoor tomato growers, but over the last few years it’s also been kiwifruit, avocados and strawberries.”
Bumblebees require very little in order to flourish. The queen can form her nest in an old rodent hole or other dry space underground which can be replicated with a relatively simple box construction containing nesting materials such as insulation padding or underfelt.
Despite the demand and growing awareness of the insect, though, one species of bumblebee is possibly on the verge of extinction. The last of its kind in the world, its plight is serious. Exact numbers of Bombus
subterraneus are unknown, but
One species of bumblebee is possibly on the verge of extinction. The last of its kind in the world, its plight is serious.
entomologist Barry – who studies the dwindling species – says the situation “is sounding rather ominous”. The species was abundant in the 1960s, with one person catching 80 queens in one day, but searches in the last two years have found just two insects. “The meagre evidence we have very strongly suggests that numbers have been decreasing rapidly,” adds Barry, who is trying to catch the bumblebees and establish man-made colonies in Christchurch in order to study and conserve their numbers.
Their disappearance here echoes their story in England over the 1970s and 1980s, leaving the New Zealand population as the only one left in the world. “Extinction here is possible. They went extinct in England after living there since the last Ice Age. They went extinct there in just a couple of decades, so there is no reason why the same couldn’t happen here. Then that raises the gigantic question of why.”
English researchers believe the loss of natural habitats and a reduced range of wildflowers – a key food source – due to intensive agriculture were the main factors. Barry says he is also concerned that in New Zealand, a devastating disease may have been introduced to the population, but no one knows for sure.
On a bigger scale, Barry says the loss of the Bombus subterraneus signals the continued “degradation of the biota of the entire world”.
“We live in a gigantic ecological web, with everything interacting, supporting and competing at the same time, but the more the fabric of that web breaks down, the more instability there is of the entire web. So the extinction of anything undermines our own security.”
The NZBCT was co-founded by Geoff Brunsden and Helen Johnson last year to raise awareness of the bumblebee’s role in that web, and in doing so, ensure that bumblebees and other pollinator insects remain plentiful in New Zealand. A passionate environmentalist, Helen says the trust is about using “the power of the bumblebee” to educate people about the importance of pollination. “Many people don’t grow their own fruit and vegetables now, and so they don’t realise how important insects such as bumblebees are.”
The trust founders, along with Barry, hope home gardeners around New Zealand will look after bumblebees, especially those in the South Island who may be able to help conserve the at-risk short-haired bumblebee. Barry recommends planting wildflowers including red clover, viper’s bugloss and Russell lupin (which is considered weedy in areas with braided river systems), as well as the Weigela florida shrub, Silene
dioica and Robinia pseudoacacia. For the other species of bumblebee, which are not currently under threat, wildflowers are also favoured, along with lavender, borage, cat mint, foxglove, geraniums, and herbs.
Gardeners can also purchase nest boxes or fully functioning colonies of bumblebees if they wish to increase the number of these super pollinators in their own gardens to aid cross pollination, or simply to help support numbers in the wild.
Bumblebees can also be counted as part of NZ Gardener’s Great Kiwi Bee Count this month to help monitor the health of the population in regions around the country.
Finally, if a stranded or sleepy bumblebee is found in the garden, a small container or lid of equal parts sugar and warm water, along with a helping hand to some nearby flowers, may just help it form a thriving colony. Such a small gesture for these giants of the pollination world seems only right in appreciation of the hardworking flight of the humble bumblebee.
Bombus ruderatus. Bombus subterraneus.