The Bumblebee Tongue and Mouthparts

Bumblebee tongue and mouthparts

The tongue and mouthparts
The bumblebee has a long, reddish-coloured tongue that is hairy at the end so is good for soaking up nectar (see right). When the bumblebee is flying the tongue is folded under its head and body inside a horny sheath formed by the palps and maxillae. In the drawing below the tongue itself is the long thing in the middle, the two outer parts on each side form the sheath, they are called the palp and the maxilla. The tongue and mouthparts are covered in tiny hairs and these hairs have pores in them. Molecules pass through these pores and stick to receptor sites on sensory cells. This is how the bee tastes and smells. The main concentration of these hairs are on the antenna and mouthparts.
On the left, the photograph shows the antennae, which are black, then in the middle the tongue, palps and maxillae.

Below left a Bombus terrestris or lucorum worker has her tongue in the nectary of a flower and is drinking the nectar. Below right shows a Bombus pascuorum queen with her tongue sheath extended out in front. Normally the sheath is folded under the body and only moved forwards to drink nectar.

In the UK Bombus hortorum has the longest tongue which can reach just over 2 cm when fully stretched. When the bumblebee drinks nectar the sheath is moved so it is facing the entrance of the flower. The bumblebee then moves towards the nectar and the tongue itself shoots in and out soaking up the nectar.

above the tip of a bumblebee tongue showing the hairy/feathery end

Bumblebee tongue and sheath.

worker of terrestris/lucorm with tongue extended into flower

If you look up at a flower against the sunlight while a bumblebee is drinking you can just see this. If you want to get a better look you can try feeding them with a solution of honey or sugar and water in a plastic pipette. Using a plastic pipette like this is also a good way to measure the length of the tongue.

In the table of tongue lengths on the right, the measurements were taken from live workers foraging. The bumblebee tongue is an elastic organ, when dissected and measured the length will be longer than those in the table. A pipette marked in millimetres and filled with a water/honey solution was offered to workers. The meniscus was moved up to see how far they would extend their tongue to reach the mixture. This work was done more than ten years ago. Now I would advise a water/sugar mixture to avoid spreading disease.

I get many e mails from people telling me bumblebees are drilling holes in the wood of their house/shed etc. the insects doing this are usually carpenter bees, not bumblebees. The mouthparts of a bumblebee are not strong enough to drill holes in wood, nor can they bite with any strength.

Average tongue lengths measured from foraging bumblebee workers.

Species	Tongue length mm
Bombus hortorum	12.0
Bombus lapidarius	6.0
Bombus pascuorum	7.6
Bombus pratorum	6.4
Bombus terrestris/lucorum	5.8

Bombus pascuorum queen with tongue sheath extended forwards.

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