Leaf beetles (Chrysomelidae) are a large, diverse group of beetles known for their vibrant colours and close association with plant life. With over 35,000 species worldwide, they display a wide range of colours, patterns, and sizes. They are typically small to medium-sized beetles, ranging from a few millimetres to about a centimetre in length. Their bodies are often domed and oval-shaped, with smooth, hard exoskeletons that can be green, metallic blue, red, yellow, or black, among other colours.
In the UK, a variety of leaf beetles from the Chrysomelidae family can be found across different habitats, including woodlands, grasslands, and gardens. Here’s a list of some notable species:
Green Dock Beetle (Gastrophysa viridula)
Commonly found on dock plants (e.g., broad-leaved dock, Rumex obtusifolius). Known for its vibrant green, metallic coloration.
Rosemary Beetle (Chrysolina americana)
Feeds on aromatic plants such as rosemary, lavender, and thyme. Originally from southern Europe, but now established in the UK. Recognized by its metallic green and purple stripes.
Tansy Beetle (Chrysolina graminis)
- Found primarily along riverbanks, especially near York. Feeds on tansy plants and is distinguished by its bright green, metallic colour. Known for feeding on cucumber and squash plants. Also vectors for bacterial wilt, a disease affecting cucurbit crops.
Mint Leaf Beetle (Chrysolina herbacea)
Primarily feeds on mint and other plants in the mint family. Green and metallic in colour, similar to the rosemary beetle..
Common Willow Leaf Beetle (Plagiodera versicolora)
Primarily found on willow trees and sometimes poplar. Small and metallic blue-green, often causes noticeable damage to leaves.
Alder Leaf Beetle (Agelastica alni)
Common on alder trees across the UK. Deep metallic blue or blue-black colour, often seen feeding in groups on alder leaves.
Brassy Willow Beetle (Phratora vitellinae)
Feeds on willow and poplar, particularly young leaves. Shiny, brassy appearance that can sometimes appear green or blue.
Blue Mint Beetle (Chrysolina coerulans)
An introduced species now established in southern parts of the UK. Has a striking blue metallic colour and prefers mint plants.
Cereal Leaf Beetle (Oulema melanopus)
Often found on cereal crops and grasses, it can be a minor pest. Blue and red coloration, slender body with distinctively long antennae.
Grape Vine Beetle (Altica lythri)
Found on a variety of plants, especially willowherbs and occasionally grapevines.
Small and metallic blue to black in color, a member of the flea beetle group.
Hazel Leaf Roller (Deporaus betulae) (closely related, sometimes included in Chrysomelidae)
Primarily found on hazel and birch trees, where it rolls leaves for its larvae.
A small, brownish beetle, it differs in behaviour as it “rolls” leaves into a tube.
Cabbage Stem Flea Beetle (Psylliodes chrysocephala)
A pest of oilseed rape and related brassica crops. Small, dark metallic blue or black, with long hind legs for jumping.
Large Leaf Beetle (Chrysolina fastuosa)
Large Leaf Beetle (Chrysolina fastuosa)
Found on nettles and often near wet habitats.
Black with metallic reflections, sometimes appearing brassy or greenish.
These species represent a range of native and introduced beetles that interact with both wild and cultivated plants. Many are associated with particular plant families, which can help identify them in specific habitats or landscapes across the UK.
Habitat and Distribution
Leaf beetles are found in various habitats, including forests, grasslands, wetlands, and gardens. They are highly adapted to terrestrial environments where plants are abundant. As herbivores, they are especially common in regions with diverse plant life, as they feed on leaves, stems, and roots.
Diet and Feeding Behaviour
True to their name, leaf beetles primarily feed on plant foliage, and some species specialize in specific plants. The larvae and adults can cause significant damage to plants, making some species pests in agriculture and horticulture. For example:
- The Colorado potato beetle (Leptinotarsa decemlineata) is notorious for feeding on potato plants and can devastate crops if not controlled.
- Flea beetles are small, jumping leaf beetles that create holes in leaves, particularly in vegetables like cabbage and kale.
Life Cycle and Reproduction
Leaf beetles undergo complete metamorphosis, passing through four stages: egg, larva, pupa, and adult. The females typically lay eggs on host plants. Larvae often feed on the same plants as the adults, sometimes targeting different parts like roots or stems.
Defence Mechanisms
Many leaf beetles have evolved bright colors as a warning signal to predators, an adaptation associated with their toxic or distasteful nature. Some produce defensive chemicals to deter threats, while others use mimicry to blend in with their surroundings or resemble other toxic species.
Ecological Role
Despite their reputation as pests, leaf beetles play essential ecological roles by contributing to plant population control and serving as a food source for various animals, including birds and other insects. Some species are even studied for biological control to manage invasive plants.