The BBKA’s Module 3 syllabus says ‘The Candidate shall be able to give: …an outline account of the life cycle of Braula coeca, its effect on the colony and a description of the differences between adult Braula and Varroa”.
This funny little creature, Braula coeca (Pronounced Browler Seeker), is commonly – but mistakenly – known as the ‘bee louse’. In fact it is a type of fly, although one which can’t, being wingless.
Below is an infographic on Braula coeca which I had a go at making using Prezi. Even though it’s not particularly complex, this took me ages! Respect to infographics creators.
If you have trouble reading the infographic, click on this Printer-friendly pdf version to see a larger version.
Braula is similar in size and colouring to a varroa mite. However, an adult Braula coeca has much more prominent legs than varroa (six legs compared to varroa’s eight) and more of a classic beetle shape with its head at its narrowest point, whereas a varroa mite is crab shaped, its legs protuding out slightly at its widest point.
Since beekeepers started treating against varroa with miticides, Braula coeca numbers have plummeted, but they used to be regularly observed riding the back of adult bees like little jockeys. When hungry, Braula will walk over the head of its host, lean forward and steal pollen and nectar from the bee’s mouth parts. It does this as the bee is feeding or exchanging food with another bee, or it can also deviously stroke the bee’s labrum (its “upper lip”), causing the bee to regurgitate a drop of fluid from its honey stomach, which the fly then eats.
Braula are particularly fond of queens, with dozens often found congregating on a queen’s back compared to typically only one or two Braula on an individual worker or drone bee. More than 180 adults have been found on a single queen (Source: University of Florida entomology department). This is likely to be because queens are fed regularly and consume greater quantities of food than worker bees.
To reproduce, the female lays her eggs – 0.8mm in length – throughout the hive, though only those laid in the cappings of honey comb actually hatch, two to seven days later. The maggot-like larvae then burrow just under the surface of the capping, feeding on honey and pollen, creating little tunnels about 1mm wide. After a short series of moults, they emerge from the cappings as adult flies, ready to climb onto an unwitting bee. Like varroa mites, they overwinter by clinging to the back of an adult bee.
As they only steal a small amount of their food, rather than feeding on their haemolymph or developing larvae, Braula are not particularly harmful to honey bees. However, large numbers of them riding on a queens’ back must be a nuisance, and the developing larvae tunnelling through the wax cappings of honey cells is a pain for beekeepers wanting to produce cut comb.
Extracted honey with the cappings removed will be fine, but biting into cut comb will reveal the characteristic white tracks of the tiny Braula larvae within the cappings. If you live in an area where Braula still survive, the way to avoid this is freezing honey comb overnight as soon as you remove it from the hive, which destroys the eggs and larvae.
- University of Florida entomology department ‘Bee louse’ page (very helpful and great microscopic photos)
- ‘What are bee lice and why don’t we see them in our hives these days?’, BBKA News, June 2016, p.219-220
The Module 3 exam is on Saturday, and I’m really not feeling confident about it. Between starting a new job and trying to find a wedding venue, I haven’t had as much time to revise as usual. I’d love to pass, but if I don’t I’ll go back to revising and retake in November.