Green  Hairstreak

The Green Hairstreak (Callophrys rubi) is a fascinating, small butterfly known as the only truly green butterfly found in the UK. Despite its bright appearance, it is notoriously hard to spot because it hides its vivid colors by resting with its wings tightly closed.

Here are some of the most interesting facts about the Green Hairstreak:

1. The "Green" is an Illusion

The brilliant emerald green on the underside of its wings is not caused by green pigment. Instead, it is a structural color created by microscopic lattice structures on the wing scales that diffract and reflect light. This means the color can change depending on the lighting and angle. 

2. They Never Show Their True Colors

While the underside is bright green, the upperside of its wings is a dull chocolate brown. The butterfly almost always lands with its wings closed to hide its brown side, perfectly camouflaging itself as a fresh green leaf. 

3. They Make Sounds and Act as "Ant Food"

The pupae (chrysalids) of the Green Hairstreak can produce an audible sound—a squeak or "chirp"—to attract ants. The ants are thought to protect the pupa (which is often hidden on the ground in leaf litter) in exchange for sugary secretions.

4. Extremely Varied Diet 

The Green Hairstreak caterpillar feeds on one of the widest ranges of plants of any British butterfly, including gorse, broom, and bilberry. This versatility allows them to thrive in diverse habitats, including heathland, moorland, and chalk grassland.

5. Territorial "Aerial Battles"

Males are highly territorial and choose a specific perch on a shrub (like a Hawthorn or Gorse bush) to wait for females. They will chase away any other insects that pass by, often engaging in complex, spiralling, upward flights in their scramble for dominance.

6. Long Pupa Stage

These butterflies are univoltine, meaning they only have one generation per year. They spend about 10 months of the year as a chrysalis (pupa) and only live as adult butterflies for a short period in the spring. 

7. They Have "False Antennae" 

As a member of the Lycaenidae family, they often have tiny, hair-like tails on their hindwings. These tails, combined with markings, act as a "false head" to confuse predators like birds, diverting attacks away from their real head to a less vital part of the wing.

8. It's Hard to Spot 

Despite being widespread in the UK and Europe, they are seldom seen in large numbers and are often overlooked due to their small size (2.6–3.3cm wingspan) and excellent camouflage.