Why Bumblebees Need Our Help

WHY ARE BUMBLEBEES SO IMPORTANT TO US!

In New Zealand we have four species of bumblebees. These were introduced from England as early as 1885 specifically to assist with the pollination of red clover. Nowadays bumblebees are also used to pollinate greenhouse and orchard crops. They are also important because they pollinate our summer gardens, our wildflowers and our crops. They are important agricultural pollinators so their decline around the world is a cause for concern. The decline has been caused by a number of factors including removal of wildflowers and flowering tress from the landscape, habitat loss, the mechanisation of agriculture and extensive use of pesticides.

The word ‘bumblebee’ is a compound of ‘bumble’ +’bee’ –‘bumble’ meaning to hum, buzz, drone or move ineptly or flounderingly. The generic name Bombus assigned by Pierre Latreille in 1802, is derived from the latin word for a buzzing or humming sound.

A single bumblebee can do 50 times the work of a honeybee and carries a bigger payload of pollen. They will also pollinate flowers honeybees can’t. For example honeybees aren’t boisterous enough to dislodge pollen from tomato flowers where as bumblebees will vigorously buzz the flower and bee rewarded with showers of pollen falling on their bodies. This technique is known as ‘buzz pollination’. In a glasshouse one bumble bee can pollinate up to 450 flowers per hour.

Bumblebees carry up to 90% of their body weight in food and the level of activity required to fly is so great they are only ever 40 minutes away from starvation. They can reach ground speeds up to 54 kms per hour.

Bumble bees are fantastic navigators and can remember landmarks to help steer them back to the hive. They will forage out to about 1-1.5 km and equally so are also happy in confined areas. They will work from daylight to dark in rainy weather and will be out and about at temperatures just above freezing. They have a unique body temperature control system which keeps them warm when it’s cold and cool in the heat.

The females (queens and workers) have a sting and only sting if disturbed or handled roughly. Generally they are not aggressive at all.  Bumblebees have smelly feet and will leave a smelly footprint to show they have been to a flower. Other bees will be able to tell if the flower has already been looted! All flowers replenish their pollen and nectar at different speeds e.g. comfrey takes around 40-60 minutes to refill where as borage takes two hours. Other flowers can take days. Once the flower is full again the smelly footprint wears off giving the green light for whoever visits next. Bumblebees only store a few days worth of food so are more vulnerable to food shortages. 

The much loved Bumblebee (bombus genus) appeals to many of us. There is something about their rambling bumbling gait and their buzzy noise that we love. They have round bodies covered in soft hair (long branched setae) called pile making them appear and feel fuzzy. They have aposematic (warning) coloration, often consisting of contrasting bands of colour. Bumblebees feed on nectar using their long hairy tongues to lap up the liquid (the proboscis is folded under the head during flight. They gather nectar to add to the stores in the nest and pollen to feed their young. Bumblebees forage using colour and spatial relationships to identify flowers to feed from.

They do not have ears however they are sensitive to the vibrations made by sound travelling through wood and other materials. When they return from a successful foraging expedition they run excitedly around in the nest for several minutes before going out to forage again.

The Bumblebees Habitat

The Bumblebee life cycle

Bumblebees are social insects and can live in nests of up to 400 bees. Each nest has a queen and will last for only one year. Bumble bees rarely nest in the same location two years running.

Spring 

In early spring the queen will emerge from a winter of hibernating to start a new nest.The first activity she has to do is to build up her energy reserves. It is very important she can find plenty of pollen and nectar rich flowers  Once she has found a suitable nest site she will rear her first batch of eggs – a group of female worker bees whose job it will be to feed the growing colony

Summer

Through out summer the queen will continue breeding bees. She may not even leave the nest during this time.
Towards the end of summer the queen produces male offspring and some new queens. 

Autumn

After mating the males die off along with the old queens and her workers.

Winter

Only the new fertilized queens survive to hibernate through the winter and establish their own nests the following year.

Identification of Bumblebees in NZ

Helping us identify bumblebees

1. Bombus terrestris. Our most common bumblebee. It occurs throughout New Zealand and can sometimes be seen flying on sunny days after frosts in milder areas. Queens, workers and males all have the same colour pattern. The tongue is short. This is the species that is mass-reared for pollination of tomatoes in glasshouses.

2. Bombus ruderatus. Occurs over most of the country but isn’t seen during winter. Colour can range from completely black to almost as much yellow as Bombus hortorum. The tongue is very long.

3. Bombus hortorum. Not present in Westland or north of about Hamilton but appears to be spreading north. An occasional bee might be seen in winter in milder areas. All castes are similarly coloured. The tongue is very long.

4. Bombus subterraneus. Our rarest bumblebee in that it occurs only in inland south and central South Island areas. It is on the wing only from about early November to late March. Queens and workers have an area of black hairs in the middle of the frontal yellowy band and males are mostly yellowy green. The tongue is long.

The photos below are from the late Dr Barry Donovan’s publication, Fauna of New Zealand No 57 Apoidea B.J. Donovan.

These images are reproduced with permission from Landcare Research

For those looking for more in depth reading and understanding, please browse these academic papers:

• The Introduction Of Bumblebees Into North Island, New Zealand
• Bumble Bee Road Toll (Hymenoptera: Apoidea)
• Development Of Hives For Field Population Increase, And Studies On The Life Cycles Of The Four Species Of Introduced Bumble Bees In New Zealand
• Distribution Of Bumble Bees in New Zealand
• Bumble Bee Species Present In The South Island of New Zealand
• Saving the shorthaired bumble bee, Bombus subterraneus

Do bumblebees like Petunia or vegetables flowers?

Here is what our Bee expert said;

Yes, two of our four species of bumble bees, Bombus terrestris and B. hortorum, have been recorded visiting Petunias. 

But whether a flower will be visited by a particular species of bee depends on a number of factors. Obviously reasonably good numbers of the desired species of bee must be present in the area, and there must also be a lack of the types of flowers most favoured by the bee – assuming the flower in question is not a favourite of the bee.

For example Bombus hortorum has been recorded visiting kowhai flowers, but around my property I have 23 kowhai trees that are flowering now, and although there are plenty of B. hortorum visiting nearby tree lucerne flowers and broad beans, I haven’t seen any on the kowhais. Also B. terrestris very readily visits kowhai, but one kowhai tree has more B. terrestris visiting its flowers than all the other 22 kowhais together. It seems that this attractive kowhai must have more nectar and/or nectar with a higher concentration of sugar, but why this should be the case is unknown to me.

Regarding your other plants, in general the flowers of brassicas (for example Rocket) are attractive to bumble bees, and also the flowers of herbs such as Basil, Celery, Dill and Fennel, and the flowers of onion-related plants, e.g. Chives and Leek. However the flowers of plants in the Solanaceae such as Capsicum, Chilli and Eggplant are not. But having said that, in a glasshouse B. terrestris very readily collects pollen from the solanaceous tomato flowers when there are no other flowers available. 

So if bees have been recorded visiting a particular flower one cannot be dogmatic as to whether that flower will attract bees, but one could say something like “can attract bees”.  

Moving a Bumble Bee Nest

Information what to do if you find a nest can be found here