Bees that may look and/or sound like bumblebees, but are not bumblebees
Recently I've been getting a
lot of e-mails from people wanting to know about bees that are obviously not
bumblebees, but may resemble them. Usually the writers are concerned that these
bees are causing some damage to their property, or are a danger to children and
pets, and naturally they want to know what to do.
Almost all of them are
classed as solitary bees, i.e. the female doesn't stick around after laying the
first batch of eggs and providing a food supply (pollen and nectar), so the
nest size is tiny. However some do nest communally either close together or
using a common entrance hole, making it look a little like they are social
These bees are generally less
hairy than bumblebees and usually, but not always, smaller. The colour and
pattern of their hairs varies, but is rarely the yellow and black seen in the
commoner bumblebee. They fall into four main groups, miners, carpenters,
masons and leafcutters.
These bees generally nest in the ground,
often in paths or lawns, and some of the lawn nesting species nest communally.
The entrance to their burrows are often marked by a small mound of excavated soil (see right. These bees are good pollinators of economically important plants such as fruit
trees and alfalfa. In reasonable numbers these bees won't harm your lawn.
There are about 100 species of mining bee in Britain, most resemble honey bees, but are smaller in size. Their burrows can be 60 cm deep. The clump of pollen takes the mother bee 6 - 7 journeys to gather. And each load is around half her body weight. Once the pollen clump is the right size she lays an egg on it.
The photograph on the left was taken in north-eastern France at the end of summer. It shows a number of nests made by mining bees, probably Colletes sp.
Some of the nests were still being used, some had been taken over by spiders and others appeared empty. It is quite common for Colletes sp. to nest in dense aggregations like this where the ground is suitable.
They cement the grains of sand together with an oral secretion plastered on the inside of the cell. Often this secretion will contain a fungicide.
There are 8 Colletes sp. in Britain. The burrows are usually less than 30 cm deep, and are dug in sandy soil. The cell at the end of the burrow is filled with honey.
Miners and carpenters
The photograph on the right was sent in by Allen H. in Tennessee, and is very interesting. When he first wrote about a small male hanging on to a big female I thought it was just the typical bumblebee mating, but said I would have a look at the photograph anyway. As soon as I saw it I knew there was very little that was typical about this photograph.
The little bee is a male mining bee, Andrena sp. who seems to have mistaken the large male carpenter bee for a female of his own species. The male carpenter seems oblivious to the male miner he is transporting as he has eyes only for the female carpenter who has been sucking nectar from flowers. And by the look of the female's body language she is less than keen for the male carpenters attentions.
There are around 360 species of Andrena mining bees in Europe and the near East, and over 500 species in North America. Most are solitary, but some do nest communally.
Xylocopa sp. (above right and below left) are also known as Giant carpenter bees. There are over 750 species world wide; mainly topical and sub-tropical. They nest in dead and live wood, and some even nest in bamboo stems. They may reuse the tunnels from a previous generation. Females will guard their nests against predators and also against other females who mat attempt to clear out a ready made tunnel and lay their own eggs.
These bees have powerful
mandibles (jaws) that can dig tunnels in wood. Xylocopa violacea (below), a huge
(20-23 mm long), black bee found in central and southern Europe nests in dead
wood and digs a tunnel up to 30 cm long containing 10-15 cells.
Xylocopa virginica (above right). In March and April the males set up territories near where the females will be emerging so that they can mate. By May all the females will have emerged and mated, and the males have nothing more to do so they all die while the females are drilling their nests. Often 2 or 3 females will occupy the same tunnel, although only one will lay eggs and provision the cells. Often this female will be a bee who emerged as an adult the previous year, but never mated. The helpers are likely to be her nieces and they will guard the nest, and probably hope to lay their own eggs in it the following year.
The photograph below right is of a Xylocopa violacea hole. This bee holds the record for laying the largest egg of any insect. Carpenters are found in
many parts of the world, and there is one very similar to this commonly seen in the USA. Naturally a large number of carpenter nests in the
structural support of a building will cause some damage, but this is unusual.
Alarming carpenter bee behaviour
One behaviour can be alarming though. The males compete with other males to
mate with females. This involves them chasing males away and chasing females to
mate. During these chases
they zoom about crashing into windows, people and anything else in their path.
Humans in the way of all this may think they are under attack, they are not,
they are just in the way. Males may also hang around waiting for adult females
to emerge, and again they behave in what might seem to us as an aggressive way,
by chasing other males away and investigating anything that gets near the exit
something may be your head, you will be buzzed around and checked
out to see if you are a rival that needs chasing away or a female that needs
mating. However there is no danger as males cannot sting, so like much male
mating behaviour it's all bluster and show.
These bees will nest in almost any cavity
which they can modify in shape with earth or other materials to suit their
requirements. Some species specialise in nesting inside snail shells, and there
is a tiny species that nests in the holes left by wood worm beetles. The
European species Osmia rufa, Red osmia is often found nesting in old nail holes and
in the mortar of old walls. Osmia sp. collect pollen in the dorsal hairs of their abdomen - similar to some leafcutters.
Others, like Anthophora retusa, on the left
construct cells using clay, sand, earth and chalk, and earth mixed with wood - whatever is at hand. Anthophora retusa looks like a small, dark bumblebee, but she has orange-coloured hairs on her hind legs. In the UK this bee appears in the early spring and flies until July, it is an important fruit pollinator.
In towns their nests can often be found between two bricks in walls. The nest on the right has only two cells, if space permitted there would be more.