2 June 2013

Nasanov Gland and pheromones

I took this picture the other day, just after I'd done a Taranov split. The bees pointing their abdomens in the air are sending a scent message to any bee from the colony that might be slightly lost, and are guiding them home.

Worker bees fanning Nasanov pheromone.
Almost at the end of the abdomen, on the segment before the sting, is a scent gland that produces attractant pheromones. It's called the Nasanov Gland.

To make sure the scent is widely distributed the bee will point its' abdomen upwards and fan its' wings - this moves the pheromone into the surrounding air, it's picked up by other bees' scent receptors on their antennae and mouthparts.

When a lot of bees are fanning this pheromone the scent can be strong enough for us to smell it too. It's lemony, not unlike Lemongrass*, Lemon Balm or Lemon Verbena. We capitalise on this by using a lemony scent in bait hives, hoping we will attract a swarm by persuading scout bees that others have already marked it as good place to live.

Bees are very sensitive to scents, for example tiny amounts of scented secretions tell nurse bees when to feed larvae or when drones are hungry.

'Lemon' isn't the only scent they use that we humans can recognise. Alarm pheromones, which are made by the mandibular gland near the mouth, can smell a bit like pear drops, nail varnish or ripe bananas. If you can smell this during an inspection it might be a good idea to close up as quickly as possible, and then try to work out why the bees are 'alarmed' or angry.

There are many reasons for a colony to be 'alarmed':
  • The colony could queenless, and lacking the 'queen substance' scent produced only by a queen. 
  • You could be taking too long. 
  • The colony could be distressed and defensive because wasps, mice or other bees are attacking it. 
  • The bees might not like the smell of something you've eaten, a scent you're wearing, or the detergent you've washed your clothes in.
Sometimes people who are diabetic will notice that bees attack them for no apparent reason, this is because of the smell of pear drops (or bananas) on their breath. Bees don't like the smell of fish either, so it's probably not a good idea to paint your nails then eat fish and chips followed by a nice ripe banana just before opening up a hive.

When bees sting there is a scent pheromone left behind by the sting gland. It stays on your skin or clothes, and can't be scraped or rubbed off. This scent tells other bees what, and where, to attack, and lingers for several days. This is why, if you've been stung, it's a good idea to first of all 'smoke' the sting site to temporarily mask the sting pheromone, and then to make sure your bee suit, hat or gloves are washed before you go near any colony again - or you could end up with a lot of bees 'pinging' and trying to sting you, which can make an inspection less than pleasant.

* Not to be confused with Citronella, which is an insect repellent.


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