The smell super-power of insects and the remarkable abilities this unlocks

What would life be like as an insect? Instead of sights and sounds your world would be filled with smell and tastes. Insects evolved around 600 million years ago in the swampy marshlands as life emerged from the ocean. To navigate the world, they developed entirely novel olfactory and gustatory receptors (for smell and taste) – providing rich information to help them fly, find food and communicate. Since then, insects have exploded – today there are estimated to be over 2 million species [1]of insect and their incredible sense of smell gives them remarkable abilities.

1. Smelling dinner 10 miles away

When we think of food we think of smell. Just the waft of apple pie can be enough to get our saliva glands going But what if the apple pie was 2 km away? Incredibly a bee can smell a single flower from 2km (1.2 miles) away[2]. Blowflies are even more impressive, they can smell food from 16 km away (10 miles)[3]. That’s a long way from the kitchen!

2. Love is in the air – from 30 miles away

It’s a big world out there, especially if you are insect sized! Finding friends and a mate in a short lifespan is crucial so insects have honed their smell superpower to do just that using pheromones (chemical signals) to communicate with each other. Females release sex pheromones to attract males which follow their nose (or rather antennae) to find love. Incredibly giant silkworm moths will follow these pheromone trails for up to 30 miles[4].

*Insects have been observed to follow pheromone trails for up to 30 miles*

3. Sharing directions (and detours)

Insects live highly social lives and they often share information using odours. If you have ever wondered why ants keep making for your pantry, it’s because they leave tiny odour signals, providing directions for those that follow. Ants can even re-route these, using a higher concentration to signal a detour or diversion[5].

4. Eavesdropping and insect counterintelligence

Pheromones can be an excellent way to find others of your species but they can be intercepted. Insect predators have evolved to eavesdrop on these signals for their advantage. Parasitic wasps tune into pheromones to smell target hosts and then fly over to lay their eggs in their target. But just as in human society, spying generates counterintelligence and insects are no different. Some insects have developed specialised receptors to warn of danger and steer clear – fruit flies have a dedicated receptor to smell wasps and avoid sites that smell like wasps[6].

*Insects communicate using smells - there are billions of possible VOCs but they still eavesdrop for advantage*

5. Smelling danger – smell, drop and roll

Smell tends to be tuned for danger as well as love. Insects are highly tuned to detect predators and also use alarm pheromones to signal danger to others in their community. For example aphids can smell ladybugs, a key predator and then change behaviours, even growing wings faster![7] They also trigger an alarm - when an aphid is grabbed by a predator, it releases a burst of a sesquiterpene called (E)-β-farnesene. Neighboring aphids immediately smell this alarm pheromone and react by dropping off the plant or moving away en masse[8].