Love is in the air: how butterflies date

To meet 'the one' among a swathe of unsuitable or unwilling partners, butterflies must adopt clever tactics.

Lepidoptera curator Dr Alberto Zilli explains exactly what it takes for a lonely insect to land that all-important meeting. 

Wear your best clothes

One of the easiest ways for butterflies to find a mate is by being as colourful as possible - a technique these insects don't need to think about.

Species that fly in the day can afford to rely heavily on colours, and their displays range from delicate pastels to iridescent blues.

Zilli says, 'Coloured wings are a signal to other butterflies. They allow insects to recognise their own species in a complicated habitat. Colours also distinguish between males and females - vital when you are looking for a partner.'

Pastel colours in butterfly wings are caused by chemicals called pigments. They absorb certain wavelengths of light and reflect others, causing the eye to see a particular colour.

Bright, iridescent colours are produced by the structure of the wing itself. Some species, such as the blue morpho, have wings that are made up of millions of tiny scales.

The scales reflect light waves repeatedly, creating a very intense colour which can appear to move with the butterfly.

Use perfume

Colours are useless in the dark, so butterflies and moths that fly at night use acoustic and chemical signalling to reach out to others.

Both males and females give off scent to communicate with each other, releasing specific pheromones to attract the right type of mate.

Zilli says, 'During the first stages of finding a partner, males optimistically chase after almost any small, moving object. This includes leaves, bees, and butterflies of any species - of either sex.

'When they get closer, they can start working out if they’ve found the right match, by judging colours, pheromones and behaviour.'

Some female hormones are so powerful that a male butterfly can sense them 10 miles away.

Fend off the competition

Male butterflies and moths can create acoustic signals or pulses to let females know they are searching for a perfect match.

These pulses have the added benefit of sounding threatening to other male moths, as they mimic the noises bats make when they hunt.

Zilli says, 'Evolution always tries to save energy, so lots of these signals work in two ways - both attracting a mate and sending away the competition.'

Males of the lesser wax moth (Achroia grisella) species are well known for singing (sending out ultrasonic sound) to advertise their availability.

The singing is either done individually, or groups of males can band together and form a choir. This competitive display behaviour is called lekking. Individuals compete with each other, allowing females to take their pick from the group.

Shut up and dance

Once a pair of potential lovers has found each other, the courtship can start.

Initially butterflies find each other using colour and sound. But at this stage a decision is made about whether to mate based on the pheromones that both sexes give out.

Zilli says, 'In many species, the female requires the male to perform a dance before she will allow him near. He delicately flies around her, whirring his wings in the hope that more pheromones waft in her direction.'

If she is impressed enough to accept, she will change her posture, letting the abdomen protrude from between her wings.

Be persistent

Males are frequently rejected by picky partners, and being determined in the face of refusal is vital. Only the luckiest butterflies are successful on the first attempt.

In some species, females prefer to wait several days after mating before looking for another partner.

Zilli says, 'It could seem that the odds are stacked against butterflies, as successful courtship relies on finding the right balance between sight, sound, smell, luck and mood. Thankfully, for most males, little else matters over their short lifetimes.'