by Flavio Winkler Ford –
Bees can be heard buzzing around flowers, such as those of willow in early spring and heathers throughout the summer. At Aigas, we have been delighted to see the first white-tailed bumblebees of the year over the last couple of weeks (March)! They are hard at work collecting food in the form of pollen and nectar. It is always nice to see the mutualistic relationship between plant and pollinator, however, bees don’t always have friendly relationships with other species, and things can get sinister!
Adult bees can be predated by birds such as blue tits and also by invertebrates, including hornets, robber flies and camouflaged crab spiders. Conopid flies lay their eggs within adult bumblebees and their larvae develop inside the bee eating it from the inside! Then there are the bee mites, nematodes, viruses, fungal pathogens and bacteria, which all infect bees. Occasionally you may come across the dug-up remains of a bumblebee nest. Badgers and other mammals are often the likely cause, as they can’t resist such a tasty buffet. Things get really interesting when you delve into the hidden world of bee nest parasites!
Oil beetles can be found at Aigas. Here is a photo of a violet oil beetle that I found outside of the staff accommodation. These charismatic beetles have an unusual lifecycle. Female oil beetles lay up to 1,000 eggs in spring. They emerge as triungulins (larva) a couple of weeks later and climb onto a flower head in wait of unsuspecting solitary bees. Triungulins will cling onto bees and hitch a ride back to the bee’s nest where they will eat stored food and even eggs. You may not be feeling very positive about oil beetles after reading this, but you should be ecstatic to find one! They are important indicators of healthy wildflower habitats and a healthy bee population, as they rely on bees for the development of their larva. Buglife even encourage you to record oil beetles for this very reason (follow this link to find out more https://www.buglife.org.uk/scottish-oil-beetle-search/)! Sadly, oil beetle populations have declined around the whole of the UK due to the loss of traditional hay meadows and other wildflower-rich habitats.
The dark-edged bee-fly (Volucella bombylans) is a very strange looking creature. It looks a bit like a cross between a bee and a narwhale. Here is a photo of a dark-edged bee-fly. Bee-flies like to play their own version of golf! Females will flick their eggs into solitary bee nests where they will develop in much the same way as oil beetle larva. Bee-flies are important pollinators in their own right and will often be seen pollinating primroses in gardens. Amazingly, female bee-flies will continue to lay eggs even if killed by a bee.
Brachicoma devia, a species of flesh fly, waits until bumblebee larvae are well fed and start to spin cocoons. When the time is right, the fly lays live young in the bee nest. The fly larva climb onto bee cocoons and feed until the cocoon has been sucked dry. A single cocoon can only support up to four fly larvae, so an infestation can lead to the death of a bumblebee colony.
The wax moth (Aphomia sociella) is regarded as the worst enemy of bumblebees in northern Europe. That’s right, there is even a species of moth whose survival strategy involves invading bee nests. The female moth lays her eggs under the cover of darkness between June and August. The caterpillars initially feed on nest debris, but quickly switch to eating wax food cells, food stores and even bee larva. Wax moths are particularly an issue to bumblebees in urban areas where nests are more easily found. The most obvious sign of wax moths is the thick, almost impenetrable, tunnels of silken thread (cocoons) that they create. This can become a home for snails, beetles, and other invertebrates.
That all sounds pretty tough for bees, but it gets even tougher; some species of bee parasitise other species of bee. Female cuckoo bumblebees invade the nests of bumblebees and kill the queen bee. These nest parasites have evolved to look like their hosts so that they can remain undetected. They are then tended to by the enslaved worker bumblebees who help to raise their young. Cuckoo bee larvae will eat the pollen brought in by host worker bees and also kill and eat the host larvae. Similarly, nomad bees, which look like tiny wasps, parasitise the nests of solitary bees.
Bees have a lot to contend with, but they have evolved to live alongside the species which predate and parasitise them. Many of these bee predators and parasites play important roles in ecosystems and are special in their own ways. We are the biggest threat to bees, as we are destroying their natural habitats through agricultural intensification and being too tidy in our towns and cities. Climate change is also bad news for bees. 13 of the UK’s bee species are now extinct and another 35 are at threat of extinction. This is a big problem for us, as 70% of UK crops rely on or benefit from bee pollination. It would cost UK farmers an estimate of £1.8 billion a year to manually pollinate crops. Fortunately, there are several ways in which you can help bees and other pollinators. One way that you can help them is by encouraging wildflowers. You could avoid mowing flowers in your lawn by taking part in Plantlife’s ‘No Mow May’ and ‘Let it Blume June’ campaigns (follow this link to find out more https://www.plantlife.org.uk/campaigns/nomowmay/)! If you really feel like turning your lawn into a wildflower meadow, you could only cut your lawn twice a year and not within the months of April to July. Don’t worry if you don’t have a lawn, as you can still help by planting wildflowers on your window ledge or a patio (follow this link to find out more https://www.wildlifetrusts.org/actions/how-create-container-garden-wildlife). Pesticide and fertilisers are a large cause in the decline of pollinators, so buying organic produce when possible and gardening organically will also help bees. The Wildlife Trusts provide more advice on how to help insects through their Action for Insects campaign (follow this link to find out more https://www.wildlifetrusts.org/take-action-insects). By following this advice, you will also inadvertently be helping all of the unusual and fascinating species mentioned above which predate and parasitise bees and their nests. The time that you save by not gardening as neatly could be spent observing and admiring the rich diversity of invertebrates that we have in the UK, and you can feel good knowing that you are doing something to help them!
