Knotgrass leaf beetle (Chrysolina polita)

Knotgrass Leaf Beetle (Chrysolina polita)

The Knotgrass leaf beetle, Chrysolina polita, is a small, attractive beetle from the leaf beetle family (Chrysomelidae), known for its smooth, shiny appearance and association with plants like knotgrass and members of the mint family. Like many in the Chrysolina genus, it plays an important role in plant-herbivore interactions within its habitat.

🪲 Identification

Size: ~5–7 mm in length
Shape: Oval, convex, with smooth, domed elytra (wing cases)
Coloration:
- Typically bronze, metallic copper, or reddish-bronze
- May appear greenish-gold in some lighting
Surface: Smooth and shiny with a polished, metallic look
Antennae: Thin and black

🌿 Habitat

Found in:
- Grasslands
- Roadside verges
- Scrublands
- Gardens and disturbed habitats
Favors areas where knotgrass (Polygonum aviculare) or mints are abundant

🌱 Diet

Both adults and larvae feed on:
- Knotgrass
- Various Lamiaceae (mint family) plants
Leaf-feeding beetle, often leaving small, irregular holes in host plant foliage

🔁 Life Cycle

Adults emerge in spring and summer
Eggs are laid on host plants
Larvae develop on the same plant, feeding until pupation
Typically one generation per year

🌍 Distribution

Widely distributed across:
- Europe, including the UK
- Often locally common in suitable habitats

🧬 Interesting Facts

The name polita means “polished” in Latin, referencing its smooth, lustrous shell
Unlike some other Chrysolina species, C. polita does not display intense iridescence but rather a more subtle, burnished shine
Its feeding helps maintain ecological balance in herb-rich habitats

The Knotgrass Leaf Beetle is a small but gleaming representative of its genus, often found quietly feeding among wild plants. Its understated beauty and role in native plant communities make it a fascinating insect for naturalists and gardeners alike.