By Colm O'Leary, Teagasc
When most people think of bees, they picture large fluffy bumblebees buzzing from flower to flower, or honeybees vigorously working around bee hives to produce honey. But did you know that nearly 80% of Ireland’s bee species don’t live in hives at all? In fact, most bee species are classified as 'solitary bees’, and many people have never heard of them.
As the name suggests, solitary bees don’t live in hives, don’t have a queen and they don’t make honey. But they’re just as important – if not more important – when it comes to pollinating crops and wildflowers. Solitary bees are the unsung pollinators that are essential to the health of our ecosystems and our food production. And right now, many of them are in trouble.
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From RTÉ Lyric FM's Naturefile, over 77 of Ireland's 100 bee species are solitary rather than social bees
Tell me more about these bees
Solitary bees are a diverse group of wild bees that nest alone rather than in hives or colonies like honeybees or bumblebees. Each female builds her own nest, collects her own pollen and nectar and lays her own eggs. There are no workers to help her, and no honey, just one female bee doing all the work.
In Ireland, we have approximately 100 species of bees, and about 80 of these are solitary. Some of the most common of these include mining bees (which dig nests into areas of bare soil) and cavity nesting bees (which use mud or leaves to seal up nests in hollow stems and holes in wood). Despite their name, solitary bees are not anti-social – many nest in loose groups – but each female is entirely independent.
Why do they matter?
Solitary bees are incredibly effective pollinators. Unlike honeybees and bumblebees that carry pollen by sticking it to their hind legs, solitary bees coat their bodies with dry pollen. Unfortunately for the bee, dry pollen falls off more easily as the bee visits flowers. Fortunately for the flower, this results in more pollen being transferred to the reproductive parts of the flower, leading to seed and fruit production. The work of solitary bees is especially important in agricultural areas, for example in apple orchards where they play a crucial role in blossom pollination and crop production.
From DW News, are we saving the wrong kind of bees?
How vulnerable are these bees?
Approximately 30% of Irish bee species are in decline. Solitary bees face many of the same threats as other pollinators: habitat loss, pesticides, and climate change, but their unique biology can make them particularly vulnerable. To start with, they have short flight ranges – many solitary bee species only travel a few hundred metres from their nest – which means there needs to be food and nesting sites close together.
In addition, many solitary bees have highly specialised diets and will only visit a narrow range of flowering plants. If those plants aren’t present, then the bees that depend on them will vanish too.
Solitary males can live for only a few days, whereas females may live for a few weeks. This means timing is everything; males only have a few days to find a mate, and females only have a few weeks to construct a nest, gather enough pollen, and lay eggs. And because the female does all the work, if she has to spend more time travelling further to find flowers, then there is less time to lay eggs.
What can we do to help them?
Solitary bees may not make honey, but their underappreciated work plays a key role in our landscapes and helps support the production of important agricultural crops. All of us can play a part, and whether you skip the occasional mowing, stop using pesticides, create a nest site or manage a meadow, it will all help in some way. Simple actions at home, on farms and in community spaces such as the following can make a real difference.
Create bee scrapes for mining bees. Ongoing research shows that mining bees like to nest in areas of bare soil on south-facing slopes. This habitat can be created by scraping the top centimetre of soil and vegetation using a shovel, then during the winter, a small bit of weeding will help reduce the plant growth in preparation for spring. A sunny bank on a field margin can be perfect.
Make a bee hotel. Cavity nesting bees can nest in hollow stems or holes drilled into wooden logs. Make sure the holes are as deep as possible (preferably 15cm deep), and having a range of diameters, from 2mm to 10mm, will also cater for a wider range of species since bees will select a hole that matches their body size. My research has shown that placing bee hotels in sunny locations about one metre off the ground is preferable. Placing a bee hotel by a fence post or the wall of a garden shed are great locations.
How to make a bee hotel
Protect existing areas of native flowers and plants for pollinators. Allow flowers to bloom by reducing how frequently you cut your grass by taking part in initiatives like No Mow May. Better yet, start managing part of your garden as a meadow by allowing the grass and wildflowers to grow and flower until late summer.
Keep flowers and nest sites close together. Placing nest sites in areas with lots of flowers will help a female bee lay more eggs since she can spend less time travelling from her nest to the flowers, and back again.
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Colm O'Leary is a PhD researcher in the UCD School of Agriculture and Food Science and a Teagasc Walsh Scholar.
The views expressed here are those of the author and do not represent or reflect the views of RTÉ
