Veins in an insect’s wing

Long main veins run lengthways from the body to the wing.

Main veins sometimes fork off into branches.

The main vein at the leading edge of the wing has no branches. It has to be very strong against the wind.

The main veins are connected by short cross-veins.

The main veins and cross veins prevent the wing from bending across the wing.

The cross veins act like tiny walls to prevent any cracks in the membrane travelling right down the wing.

Different insects have different patterns of veins.

The study of insect wings is called

Cross-section of an insect’s vein

The wing has two thin membranes supported by veins, which follow channels in between.

The tube of the vein (the cuticle) is made of a very strong material called chitin. It is shaped like a bucket to carry blood and some important body parts.

Inside the main veins is a trachea, which brings oxygen to the wing.

The main vein also carries a nerve, which responds to flight.

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People who study insects usually examine them against a white background because they are interested in the patterns of the veins.

If you use a black background beautiful colours are revealed. This is called iridescence.

Each species of insect has a different pattern of colours which helps them identify each other.

Different shapes and spaces in and between the two wing membranes behave like prisms, separating white sunlight into its rainbow of colours.

A wasp and a fly on different coloured backgrounds

Iridescence: How it works.

Light travels in invisible wave through the air.

When sunlight passes from the air into another material such as glass, it slows down.

If the light, which is travelling in a straight line, hits the glass at an angle instead of dead-on, it bends (refracts).

Glass prisms have slanted sides, which bend the light.

Within white light there are seven hidden colours and each colour has a different wavelength.

The lower the wavelength, the bigger the angle it bends.

Violet light has a lower wavelength than red light.

Red gets bent the least, violet the most, with all the other colours in between. This causes the colours to fan out into a rainbow.

Diamonds in the SunlightIridescence in Insect Wings

Iridescence in wings from a variety of species of flies (left) and small wasps (right).

The two membranes of the insect’s wing are full of different microscopic shapes and structures, which behave a bit like tiny prisms.

Light hitting the top membrane is bent by a shape in the membrane, travels to the bottom membrane where it is bent again. All the bending makes the beautiful colours.

The trick to seeing them is the background. This is why flies which fold their wings along their dark abdomens show very bright colours in the sunlight.

There is never any red. Insect eyes can’t see red so they don’t need red patterns to identify themselves.

Under the microscope…

Shapes and structuresDragonfly wing membrane

Different shapes result in different colours.

Iris, Greek Goddess of the Rainbow

The word iridescence is linked to Iris the Greek Goddess of the sea and sky.

Iris is often shown filling the clouds with water ready to rain down upon the world below.

Her name has a double meaning:

Iris the Rainbow

Eiris the Messenger