Honey Bees Have Hairy Eyes

The bodies of honey bees are completely covered in hair – even the eyes!  So:

• why do honey bees have hairy eyes, and
• how does this interesting feature assist them?

The importance of hairs on the eyes of honey bees

Firstly, it should be noted that not all bee species have hairy eyes, but honey bees certainly do.  Another group of bees that are known to have hairy eyes are the sharp-tail bees belonging to the Megachilidae bee family.

At first glance, the hairs are barely visible.  However, thanks to some excellent photographs sent to me, courtesy of Isaias Sanchez (USA), we can get a good look at the hairy eyes of the honey bee (thank you Isaias!).

What is clearly visible on close inspection of these fabulous images, is that the eye is not only surrounded by hairs, the hairs can also be seen on the actual surface of the eye itself.

More images from Isaias below.

Why do honey bees have hairy eyes?

The legs, head and bodies of honey bees (like all flower-foraging insects) get covered in millions of grains of pollen when they are visiting flowers. 

This is a deliberate process and part of their method of collecting pollen.  The hair on the eyes of the honey bee is important because the bees’ eyes become covered with pollen too.  Having hairy eyes prevents the pollen becoming stuck directly to the eye surface. 

However, if the pollen was not removed from the eye hairs, then it would become difficult to fly and to navigate.  Therefore, honey bees must remove the pollen from their bodies - and especially their eyes, by transferring the pollen to corbiculae (pollen baskets) on their hind legs for transport back to the hive. 

How do honey bees clean the pollen away from their eyes?

Honey bees use their legs to clean themselves.

A study (“Honey bee hairs and pollenkitt are essential for pollen capture and removal”, by Amador et al, published in 2017¹) used specialised filming techniques (high speed videography) to show honey bees grooming themselves and transferring pollen from the eye hairs to the hind legs.

They also demonstrated the importance of a sticky fluid on pollen grains known as pollenkitt.  Pollenkitt has an odor that attracts pollinating insects, whilst possibly helping the pollen grains to adhere to the insect’s body.

In particular, the scientists were interested to know how many ‘swipes’ of their legs over the eyes and body were required by the bees to transfer the pollen onto their hind legs.

What did they find?
Firstly, the scientists showed that honey bees seem to have a pre-programmed method of cleaning, which doesn’t vary from bee to bee and is not dependent on how dirty the bees are, nor on how much pollen is covering them.  The bees always swipe their eyes in the same way, using their forelegs to swipe across the eyes and antennae.

Furthermore, it takes between 10 and 20 swipes to fully clean the eyes and antennae.

The scientists also showed that pollen grain size is important in cleaning: very small particles of pollen can slip down lower into the spaces between the hairs on the bees’ eyes, whereas larger pollen particles remain suspended near the tips of the eye hairs, and so can be easily removed and collected.

The hairs on the bees’ forelegs are ideal for the job of eye grooming, since the hairs on the legs are slightly longer than the eye hairs, so that they can reach into the spaces between the eye hairs to collect as much pollen as possible.

 

Reference:

(1) Guillermo J Amador, Marguerite Matherne, D'Andre Waller, Megha Mathews1, Stanislav N Gorb and David L Hu : Honey bee hairs and pollenkitt are essential for pollen capture and removal; March 2017; IOP Publishing Ltd - Bioinspir. Biomim. 12 026015.