By Athayde Tonhasca
In 2005, the buff-tailed bumble bee (Bombus terrestris) came out first in a poll to elect UK’s favourite insect. This wasn’t surprising: the buff-tailed is one of the most common bumble bees in the country. It is relatively large, easily recognisable and one the first bees to be seen in spring. So you could say this species is an ambassador for all those lovable and cherished bees: “surely, everyone knows the great furry bumble bee, that gentle giant of the blossoms, that somehow awkward, slow, bumbling bear of a bee” (Brian L. Griffin). Beatrix Potter probably had the buff-tailed bumble bee in mind when creating Babbity Bumble.
Beatrix Potter’s Babbity Bumble in The Tale of Mrs Tittlemouse, 1910. Image in the public domain.
This bee is an excellent pollinator of a variety of crops and wildflowers, especially because of its ability to extract pollen that is firmly packed into the flowers of plants such as tomatoes, blueberries and aubergines. The buff-tailed is resourceful and adaptable: it forages over long distances, is not too sensitive to bad weather or picky about habitats. These characteristics help explain why their numbers remain strong and their populations seem to be expanding, while some bumble bee species have suffered declines.
Bombus terrestris. © U.S. Geological Survey Bee Inventory and Monitoring Lab.
In the 1980s, Belgian and Dutch companies developed techniques to rear bumble bee colonies on large scales, and an industry worth millions of pounds was born. Mass-produced buff-tailed and other bumble bee species replaced labour-intensive mechanical methods of pollination, and today every European tomato is pollinated by a captive-bred bumble bee. Commercial bumble bees made their way to farmers in the Americas, Japan, Australia and other countries to pollinate greenhouse crops such as tomatoes and peppers. And then trouble began.
The qualities that make the buff-tailed so well suited to its native habitat are the same that make it an invasive species elsewhere. When imported buff-tailed bees escape from greenhouses – and insects always escape – they become established and outperform native pollinators in the search for nest sites and food. They also carry novel diseases that are transmitted to the local fauna.
The impact of these man-made invasions has been demonstrated nowhere better than in South America. The buff-tailed was introduced to Chile in 1998, and thanks to a dispersal rate of up to 200 km per year, it rapidly invaded Argentina and spread out through most of the country. It is expected soon to cross into Uruguay and Brazil.
Brazilian Extension Service ‘wanted bee’ poster encouraging the public to notify sightings of buff-tailed bumble bees. Image in the public domain.
Wherever the buff-tail arrived, the native Patagonian bumble bee (Bombus dahlbomii) declined sharply or disappeared altogether, whether because of competition or infection by a parasitic protozoan brought in by the buff-tailed. Nobody knows for sure. As a result, the Patagonian bumble bee, the world’s largest, in now on the list of globally threatened species. The ecological damage caused by the buff-tailed goes further: this interloper pollinates and possibly helps the spread of invasive plant species, and reduces the volume of nectar available to hummingbirds.
A Patagonian bumble bee. © U.S. Geological Survey Bee Inventory and Monitoring Lab.
Similar scenarios have played out in the USA and Japan, so today many countries prohibit the importation of buff-tailed and other exotic bumble bees. Mass-produced bumble bees have an undeniable economical value, but they also have been identified as one of the emerging factors affecting global diversity.
The buff-tailed bumble bee is another Dr Jekyll and Mr Hyde tale of unintended consequences of species introductions. There may be compelling reasons to do it, but the possibility of harm should never be ignored.
Scottish pollinators 