When we fill our homes with fragrance, whether it be with an electronic device, a reed diffuser or simply a drop of essential oil on our pillow, we can sometimes forget that nature was there first. Yes, filling the air with attractive smells was something the natural world came up with earlier…a lot earlier.
But to take a step back for a moment – what exactly is an aroma?
Our human sense of smell comes from specialised sense cells found in the back of the nose, these are connected directly to the brain. The thing we’re smelling releases particles and these travel through the air. Only when these particles enter the nose and stimulate the nerve cells, sending messages to the brain, are we aware of the smell of a rose, tonight’s dinner cooking in the kitchen or indeed that pair of smelly socks!
Throughout nature odours are used as a means of transmitting a message – the nose possessed by animals is one kind of ‘receiver’ of this message, there are others though, which are even more sensitive, such as the antennae of some insects.
Flowers provide, what are probably the most familiar and best loved examples, of nature’s fondness for fragrance. We tend to find both the sight and smell of flowers attractive, but they’re not really for us. Of course it’s all about pollination.
Plants go to great lengths to swap genes, in the form of pollen, with others of the same species. They’ve found some willing helpers in achieving this goal – namely insects (although birds, bats and other sometimes play a role).
Plants came up with showy colourful flowers – a kind of advert directed towards their pollinators – “step this way for your free gift of delicious, sweet nectar”. The insects don’t usually bother with the “fine print” – “and by the way, you’ll also be delivering this package of pollen to my neighbours.”
So where does the fragrance come in? Well many plants underpin the visual signals with odours to help them stand out from the floral crowd. It’s a beautiful example of co-operation – a win-win for flower and pollinator. The insect gets the nectar ‘freebie’, while the flower gets to ‘borrow’ the insect’s ability to fly and so to help pollination.
These botanical perfumes are particular to a given type of plant, which is why certain flowers have their own distinct smell, and the particles are lightweight (compared to air) so as to be easily dispersible. They are often released at certain times of day – or in the case of flowers like the Evening Primrose, at night.
Moths are important pollinators, most are on the wing at night to avoid bird predators – for this reason these floral aroma diffusers release their fragrance at night when visual signals are much less effective.
Many moths are themselves examples of ‘fragrance-fans’ in the insect world. This is why the males often have distinctive and conspicuous feathery antennae – this is the moth’s ‘nose’, used in finding a female.
Female March Moths really go to town when it comes to natural aroma diffusion. Their strategy is so effective that they’ve done away with the need to fly! The wingless females climb up a tree and release their pheromones. Male March Moths are able to detect tiny quantities, even when a mile away, and so find their way to the female – enabling mating to take place.
There are many other examples of the use of fragrances as messages in the world of plants and animals. Laying a trail in ants, marking territory in some seabirds, queen bees effecting the behaviour of her workers…to name just a few.
One thing is clear – we live in a smelly world!
So next time you switch on your aroma diffuser – remember nature got there first!
Photographs by Bernard Spragg and Phil Barnett