On sunny days you may have noticed a few bumblebees foraging
on the early spring flowers. They are
most likely to be the fairly large buff-tailed bumblebee, or the tree bumblebee
that are well known for emerging early from hibernation. Most other bumblebee species emerge a bit
later. However, this column is not about
bumblebees, but about their lesser known cousins, the solitary bees.
There are about 250 species of bee native to the UK – The
honey bee, 24 bumblebee species, and 225 solitary bee species. Probably the reason that many people don’t
know about solitary bees is that many of them are very small – only a few
millimetres long and look more like wasps.
The larger ones may also be overlooked, but for a different reason; they
are furry and look like small bumblebees.
So this raises a couple of questions – how do you tell the difference
between solitary bees, wasps, and bumblebees.
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| Yellow-legged Mining Bee - Andrena flavipes |
The really telling difference between solitary bees and
wasps is their diet. Wasps get their
protein from other insect species, whereas solitary bees are vegetarian and
only eat pollen. Sadly, however, both
are partial to a quick slurp of nectar, so if you see one visiting a flower,
you can’t be sure whether it is taking nectar, pollen, or both. Fortunately, the female solitary bees tend to
keep the pollen conspicuously around their bodies, some species on their legs
and some species under their abdomen, and provided the pollen is yellow enough,
it should be easy to spot.
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| Tawny Mining Bee (female) |
Telling solitary bees from bumblebees is a bit trickier, and
the only positive way of doing it is to be familiar with a few species and
their habits so that you can learn which is which. If you have a flowering currant in your
garden, it will almost certainly be visited by the Hairy-footed Flower Bee (Anthophora plumipes). This looks like a small black bumblebee with
yellow hairs on its hind legs where it collects its pollen. Another one to look out for is the Tawny
Mining Bee (Andrena fulva). The females emerge in early spring and you
will often see them cruising an inch or two above your neatly clipped lawn
(yes, me neither!). They are an
unmistakable rich tawny gingery colour and they are looking for somewhere to
nest. The nest will be a neat straight
hole between tufts of grass and it will be surrounded by a small volcano of
excavated earth.
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| (Hairy-footed) Flower Bee - Anthophora plumipes |
It is the habits of the solitary bees that set them apart
from other bees. Honey bees and
bumblebees are social bees. They found a
colony of worker bees that will help to gather nectar and pollen to feed the
growing brood. Honey bees put aside
nectar in the form of honey to see them through to spring because most of the
colony survives the winter in the hive.
It’s a habit that beekeepers and the rest of us are grateful for. Bumblebee colonies don’t live through the
winter and once the workers have helped the queen to raise the male and female
bees that will found the next generation, the colony dies off. Only the newly mated queens survive the
winter. Solitary bees have no workers to
help them. When the female is fertilized
in spring, she digs a hole – in wood, soft mortar, or earth, depending on the
species – and then lays an egg at the bottom.
Alongside the egg she deposits a pile of pollen, and then closes off the
cell before laying another egg, piling in more pollen, and sealing off the
cell. She will carry on doing this until
the hole is full. That year’s males and
females then die off. The following
spring, the egg nearest the end starts to get warm, the egg hatches into a
larva which eats the pollen, turns into a chrysalis, then the adult male or
female emerges from the chrysalis, bites through the seal, and goes off in
search of a mate. Then the next egg
hatches, and so on. The material used to
seal off the cells varies from species to species. Many use mud, but if you see small
semicircles cut out of your lily leaves then it is probably a leafcutter bee
that uses the lily leaves to seal off each cell.
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| Red Mason Bee - Osmia bicornis |
One way to attract solitary bees to your garden is to put up
a bee hotel. You are probably familiar
with these which have bunches of short lengths of bamboo built into a wooden
box. These are ideal for solitary bees
and if you put them less than six feet from the ground on a south or west
facing wall, you are almost guaranteed to see the cells filling up. This time of year is an ideal time to put
them up as well.
The reason that you may want to put one up is that solitary
bees are great pollinators. If you look
at your fruit trees or bushes when they are in flower you will see that they
are being pollinated almost exclusively by solitary bees. So put up a bee
hotel, enjoy watching the bees visiting it, and enjoy a bumper crop of
apples. Isn’t nature brilliant?!
For links to fact sheets about the species pictured visit -
http://hymettus.org.uk/information_sheets.htm
