Why Do Bumblebees Dig In The Ground?

Earlier this year I was asked during one of my talks “Why do bumblebees dig in the ground?”

The lady was quite sure it was a bumblebee she had observed, rather than a mining bee, which may be seen burrowing into soft soil to create a nest. 

In asking the question, she wanted to know why the bumblebee was digging – whether it was to create a new nest, or whether the bumblebee was digging a hole for the purpose of hibernating.

In studying bumblebees, scientists have uncovered several reasons why bumblebees may dig in the ground. 

Why Do Bumblebees Dig In The Ground?

Some species of bumblebee may be observed to dig holes in the ground.  Generally, it will be either because the bumblebee is parasitized, or indeed, the bumblebee was creating a small area in which to hibernate.  But how do we know which?

Bumblebees Parasitized By Conopid Flies Or Nematodes

Some species of conopid flies affect the behaviour of some species of bumblebee, and generally workers rather than queen bumblebees.  Female conopid flies rest on flowers and attack bumblebees in the air, or foraging on flowers.  Eggs are deposited into the body of the bee where they grow and develop.

Before dying, the host bumblebee may dig into the soil about 5-10 cms, where the conopid flies are now able to hibernate to remerge the following year.


Nematodes (Sphaerularia bombi)

These parasites live and mate in the soil, and it is the females which attack queen bumblebees usually during their winter hibernation, but more rarely they are also believed to attack early emerging queens.  The female nematode is fertilized, and releases its eggs into the body of the bumblebee queen. 

The bumblebee is sterilised as a result of the infestation, and her behaviour alters.  It is suggested by some that instead of searching for nesting sites, the queen searches for hibernation sites, although scientists do not necessarily agree on this point.  Some suggest the queens search for both hibernation and nest sites, yet dig shallow holes in situations unsuitable for either.  However, the juvenile nematodes are  released into the soil via the bumblebee queen’s faeces. 

It is suggested that in some cases, infestation may spread from one queen to another, when an uninfected queen inspects a hole dug by an infected one, whilst searching for a nest site.


Bumblebee Queens May Dig In The Ground To Hibernate

Toward the end of a bumblebee colony life, new queens will emerge.  They will mate and feed to prepare themselves for winter hibernation.


Ted Benton writes in his book ‘Bumblebees’:

“Fertilised queens continue to feed and to return to the parental nest, building up their fat store – large, whitish clumps of cells, which eventually fill much of the abdominal cavity.  They also fill their honey-stomachs prior to settling into their chosen place for hibernation.  Little is known about where or when the different species hibernate.  Favoured places are said to be north-facing banks, where they dig into deep leaf litter, or into loose soil, forming a small chamber.  In some species at least, the fertilised young queens enter their winter quarters as early as July or August, but individuals of other species (such as B. pascuorum and B. terrestris) may be seen on the wing well into October.”

In the scenario described by the lady, I suspected the bumblebee was actually parasitized, for the simple reason that I believed it was too early for hibernation to be occurring.

Do bees sleep?
Apparently they do, but how do we know?


Bees eat pollen and nectar

- everyone knows that!

But what else do they eat?


Go from Why Do Bumblebees Dig? to


Why do bees buzz?

Bees And Pollination

Pollination – A Love Story That Feeds The Earth

How Can I Help The Bees?

Gardening For Bees

Bumblebee Nests

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