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Bombus transversalis by Mongabay

Bumblebees of the World Blog Series… #2 Bombus transversalis

A South American Bumblebee, Bombus transversalis

by Darryl Cox, Senior Science & Policy Officer

This month our bumblebee world tour stays in South America, although we are heading north from Patagonia into the Amazon basin, where our species in the spotlight is the Amazonian bumblebee, Bombus transversalis.

Fact File

Latin name: Bombus transversalis

Common names: None

Colour pattern: Queens and workers are black with two bright golden-yellow bands on the thorax, one yellow band towards the rear of the abdomen and a black tail. Males have similar banding, although the yellow is paler and the bands are more extensive on the thorax.

Favoured flowers: Unknown

Global region: Western Neotropical, Eastern Neotropical

Geographic distribution: South America – Brazil, Bolivia, Colombia, Ecuador, Peru

Conservation status: Least concern

Bombus transversalis is an impressive Amazonian specialist which exists in the tropical rainforests and wet lowlands of the Amazon basin. One of the most fascinating things about this species is its ability to survive and thrive in the most challenging of environments. Most bumblebees living in the tropics are known to operate at cooler, higher altitudes, and with good reason, the Amazon basin is well known for tropical temperatures, near maximum humidity and receiving copious amounts of the wet stuff (they don’t call it a rainforest for no reason)! Given that bumblebees evolved in temperate regions, it’s not hard to see then, that nesting on the rainforest floor is possibly one of toughest tasks for any bumblebee species on earth. Even if they can successfully avoid being flooded and washed away, they then have to raise their young in extreme temperatures and high humidity, compete for food in one of the most biodiverse places on the planet, and evade predation from numerous potential foes, including army ants!

To deal with these challenges Bombus transversalis must build a unique nest. The first step is for the nest-searching queen to find the perfect spot – she needs somewhere on dry land that is unlikely to flood and has some existing structures of roots and shoots. These structures are vital foundations for the queen and her new colony to build their home around – a construction which must be able to withstand daily deluges and an annual precipitation rate of up to 3000 mm. To make the site waterproof Bombus transversalis workers engage in a unique behaviour of foraging for leaves, often by sweeping short trails or areas in pairs. Using their mandibles, they then cut the leaves into manageable pieces and weave them into a roof canopy around the existing supports. The end result is a large dome of interwoven leaves which is nicely camouflaged among the leaf litter of the rainforest floor. This thick thatched roof prevents water from getting in, and also means that potential predators like army ants must come through the sole opening, where they will be faced with several guards.

Professor Sydney Cameron who has spent time studying these fascinating bumblebees described the above nest in detail: ” The size of this particular nest canopy is 86cm left-right, 69cm front-back, 35cm high and 5cm thick. It is constructed of leaves, small twigs and rootlets, interwoven to fashion a conical protective canopy, which covers the brood beneath. It is entirely waterproof and constructed by a behavioral caste of workers, who also maintain the nest canopy, keeping it clear of debris that may fall from above. Note its striking resemblance to some formicine (wood ant) nests.”

Inside the nest there are more leaf layers to the canopy and an ingenious air space before the last layer which allows the bees to control the humidity, leaving the internal chamber completely dry and perfect for incubating brood. Colonies which get this bit wrong have damp nests which are prone to fungal growth. Constant temperature management is key and there will often be bees positioned at the edge of the nest using their wings to fan cool air inside to prevent the nest from overheating.

Successful colonies grow to full strength during the wet season and switch to rearing new queens and males once the dry season begins. Although their life-cycle is seasonal with colonies dying out during the dry season, their nest sites are often so well-built that they remain in place for several years. As such it is not uncommon to find a new queen starting a new colony in a pre-existing nest – something which is fairly unusual for most other bumblebees, but likely gives Bombus transversalis queens a great advantage in the Amazon.

Bombus transversalis is a true pioneer bumblebee species. Through its unusual nest construction, it has managed to survive in one of the toughest places to live on earth.

Links to further information:

IUCN Redlist page

Natural History Museum species account

Natural History Museum Bombus – Bumblebees of the world homepage

Taylor and Cameron (2002), Nest construction and architecture of the Amazonian bumble bee (Hymenoptera: Apidae) in Apidologie Vol 34: 321-331

Cameron, S.A. & J.B. Whitfield. 1996. Use of walking trails by bees. Nature 379: 125.

Cameron, S.A., J.B. Whitfield, M. Cohen and N. Thorp. 1999. Novel use of walking trails by the Amazonian bumble bee, Bombus transversalis (Hymenoptera: Apidae). In Byers, G.W., R.H. Hagen and R.W. Brooks(eds.), Entomological Contributions in Memory of Byron A. Alexander. University of Kansas Natural History Museum Special Publication 24: 187-193. 

Acknowledgements

Many thanks to Paul Williams of the Natural History Museum, London, and Sydney Cameron of the University of Illinois, Illinois, US, for their help and advice.

Shrill carder bumblebee (Bombus sylvarum) by Daisy Headley

Shrill carder bee project blog

A queen shrill carder bumblebee on a purple flower

18 February 2019

by Rosie Earwaker from Buglife, Back from the Brink’s Shrill Carder Bee Project Officer

Hints of spring are in the air. Bulbs are peeking up through the soil, with plenty of snowdrops, daffodils and crocus already in flower. Sightings of Buff-tailed bumblebees in gardens are more and more frequent as the days grow longer. It won’t be long now until different bumblebee species join them, although we will have to wait a couple more months until the high pitched buzz of our Shrill carder bee returns. It certainly won’t be a silent spring this year, but where will we be in 100 years’ time?

You may have seen the headlines recently about a study predicting that we could lose 41% of the world’s insect species in the next few decades. If the rate of loss continues, this could mean that within a century there will be a very small proportion of insects left on the planet. This is staggering and would be catastrophic to life on earth.

To those of us who study insects, this so called “insectageddon” is sadly nothing new; study upon study has been documenting these declines for years, decades even. However, this recent review paper has gone one step further, bringing all of this research together to really put a spotlight on the challenges we are currently facing. Habitat loss, pesticides and climate change are some of the main factors driving these extinctions. So what can be done?

We need to start taking biodiversity loss more seriously. This isn’t just for the politicians at Westminster and across the globe to action; you can also make a difference. From planting pollinator friendly plants and ditching the slug pellets, to shopping for more local, seasonal produce. Small actions can make a big difference.

Headlines like this highlight the importance of initiatives like Back from the Brink and the work of wildlife conservation organisations such as Buglife helping the “small things that run the planet”. There are plenty of ways to get involved with Back from the Brink, including volunteering opportunities. We are always keen to have more people on the look out for Shrill carder bee and helping to monitor bumblebees through the BeeWalk Scheme, which is vital to our understanding of how these creatures are faring.

Keep an eye out for forthcoming bumblebee identification training courses and lots of exciting surveys over the spring and summer. I start this year with a reinvigorated passion for saving our precious insects and I hope you do too.

Bombus affinis by USFWS

Bumblebees of the World Blog Series… #3 Bombus affinis

The Rusty patched bumblebee, Bombus affinis

By Elizabeth Franklin, Bumblebee Researcher, Guelph, Canada

This month’s Bumblebees of the World blog is written by Bumblebee Researcher, Elizabeth Franklin, from the University of Guelph, who focuses on the plight of a critically endangered bumblebee in North America.

Fact File

Latin name: Bombus affinis

Common names: Rusty patched bumblebee

Colour pattern: Workers, queens and males have a yellow collar, black band or circle followed by another yellow band on the thorax. Workers and queens have two, mostly yellow bands at the top of the abdomen whereas males have a rusty patch on the top of their abdomen giving the species its name.

Favoured flowers: Generalist but reported on hyssops, prairie clovers, sunflowers, blueberries, the apple family and goldenrods.

Global region: East Nearctic region (North American temperate region)

Geographic distribution: Canada (Ontario), United States (Wisconsin, Virginia, Tennessee, Ohio, Iowa, Indiana, Illinois, Connecticut, Maryland, Massachusetts, Minnesota)

Conservation status: Critically Endangered

Bombus affinis or the Rusty patch bumblebee is a large, short tongued, bumblebee that was, until relatively recently, abundant throughout its range in North America and Canada. Like many other bumblebees, it nests in underground cavities but its queens emerge earlier than those of many other North American bumblebee species. Bombus affinis used to be so abundant that there are reports of them within Toronto. However, Bombus affinis has now been recognised as Critically Endangered by the ICUN after an >80% decrease in its former range. Its endangered status has been recognised in Canada since 2014 and the United States since 2017. Bombus affinis is the first bumblebee to be recognised as endangered in the United States and this status was only awarded after extensive public petitioning through the Xerces Society.

The reasons for the decline of Bombus affinis are not completely clear but pathogen spill over from managed bumblebees for greenhouse pollination is hypothesized as the major cause. The decline of this bumblebee and its close relatives correlate closely with the timing of increased infection rates of a bee pathogen Nosema bombi, thought to originate from imported commercial bumblebee colonies. In addition, urbanisation, intensification of agriculture, pesticides and climate change are thought to have also contributed to this bumblebee’s decline.

The last recorded sighting of the Rusty patch bumblebee in Canada was in 2009. Since then increased survey efforts have detected Bombus affinis in the Northern United States but have yet to find evidence of this species in its former Canadian range. This increased surveying is largely due to the extensive contributions of citizen scientists sending their photos to Bumblebee Watch for expert validation. Records are collected for all North American bumblebee species but the map below just shows the validated records for Bombus affinis.

The contributions of citizen scientists have allowed experts to find the strong holds of Bombus affinis and protect those populations. These areas and their Bombus affinis populations are now being studied to gain insights into how this species can be conserved and why they are declining elsewhere. In addition to this, scientists and conservation organisations have greatly invested in public engagement, encouraging citizens to grow pollinator gardens and contribute to the Bumblebee Watch programme. The story of Bombus affinis illustrates what we, as the public, can do to raise awareness, protect and hopefully restore our endangered bumblebee species.

Links to further information:

IUCN red list

NHM Bumble bees of the world

Xerces Society Bombus affinis

A ghost in the making: Searching for the Rusty patched Bumblebee

Group of buff-tailed (Bombus terrestris) males by Gaynor Griffiths

Smelly male bumblebees!

A group of Buff-tailed bumblebee males huddled together asleep on a flower.

By Cathy Horsley, Conservation Officer West Country Buzz

This summer, I learnt that different species of male bumblebees have different scents. I use a marking cage to examine bumblebees on my surveys to get a good close up look to identify them, and the male bees sooner or later released a puff of perfume.

Red-tailed bumblebees and Early bumblebees have a pleasant citrus smell, whereas the Buff-tailed bumblebees are more like smelly feet!

The odour comes from the release of pheromones, which are chemicals used to attract queens. By having their own distinctive aroma, males can be sure of attracting females from the same species.

Ever since Darwin’s day, and even earlier, male bumblebees have been observed following a set flight path. They tend to follow a linear circuit and pause at various places along the route to deposit a drop of pheromone. It has been noticed that males will temporarily leave their flight path, often in the early afternoon, to refuel on flowers. Different species will fly at different heights, or at different times of day, which also helps males to find the right species of female. By attracting queens to a particular place, males also avoid trying to mate with workers. Patrolling males on the lookout for queens is a fascinating subject, not least because although this is often observed, mating is rarely seen.