Insects diurnal

Tansy Beetle

Chrysolina graminis

Known as the 'Jewel of York,' this rare and radiant beetle is a masterpiece of natural iridescence. Discover how to spot this metallic green wonder in its riverside home.

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Quick Identification

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Size

7.7–10.5 mm (0.3–0.4 inches) in length

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Colors

Brilliant iridescent emerald green with a coppery or golden metallic sheen; both sexes appear similar

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Key Features

Bright metallic green coloration with a coppery tinge
Distinctive 'pitted' texture on the elytra (wing cases)
Rounded, oval body shape
Strongly associated with the Tansy plant

When You’ll See Them

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Activity pattern diurnal

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Peak hours 10 AM – 4 PM

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Season April–September

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Diet Specialized herbivore primarily eating the leaves of the Tansy plant (Tanacetum vulgare), though they occasionally feed on Water Mint or Gypsywort.

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Habitat Wetland margins, riverbanks, and damp floodplains where host plants are abundant.

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Behavior

The Tansy Beetle is often referred to as the 'Jewel of York' due to its stunning iridescent appearance and its primary stronghold along the River Ouse. These beetles are relatively sedentary and are poor fliers, often spending their entire lives within a few hundred meters of where they hatched. They emerge from the soil in early spring to feed and mate, with their lifecycle intimately tied to the seasonal growth of their host plants.

During the day, they can be found basking on the upper leaves of plants to soak up the sun's warmth, which aids their digestion and activity levels. Despite their bright colors, which might seem conspicuous, the iridescent sheen can actually act as a form of camouflage among the shimmering, dew-covered leaves of wetland vegetation. They are generally solitary but may congregate in large numbers on a single healthy clump of Tansy if the habitat is favorable.

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Camera Tips

Capturing the Tansy Beetle requires a specialized approach because of their small size and specific habitat. To get high-quality footage, you will need an AI-powered camera with a dedicated macro lens or a very short focal distance (ideally 5–10cm). Standard trail cameras will likely produce blurry results. Position your camera on a tripod or a ground-stake directly facing a healthy clump of Tansy foliage, focusing on the upper third of the plant where the beetles prefer to bask.

Lighting is the most critical factor for this species. Their metallic green color is created by the structural properties of their shell, meaning they look most vibrant in direct, bright sunlight. Aim your camera so the sun is behind the lens, illuminating the beetle's back to capture that signature golden-copper glow. If your camera has adjustable settings, a high shutter speed is beneficial to capture the crisp detail of the pitting on their wing cases even if they are crawling.

Timing is everything when looking for the 'Jewel.' The best months are May and June when the first generation of adults is most active, and again in August when the new generation emerges. Because they are flightless, you don't need to worry about them flying away quickly, but they are sensitive to vibrations. Set your camera to a 'Time-Lapse' or 'Motion Trigger' mode with high sensitivity. Since they move slowly, a short video clip (10-15 seconds) is often more rewarding than a still photo, as it captures the shifting colors of their iridescent shell as they move through the light.

Similar Species

Species that look similar or are commonly confused with Tansy Beetle.

Mint Beetle

Smaller and lacks the copper highlights of the Tansy Beetle; almost exclusively found on garden mint plants.

Rosemary Beetle

Identified by its distinctive metallic purple and green longitudinal stripes, typically found on rosemary or lavender.

Green Dock Beetle

Much smaller (4-6mm) and lacks the deep pitting on the elytra found on the Tansy Beetle.

Frequently Asked Questions

Tansy Beetles are diurnal and are most active during the warmest part of the day, typically between 10 AM and 4 PM, when the sun is brightest.

If you live near a known population (such as the River Ouse in the UK), planting Tansy (Tanacetum vulgare) in a damp, sunny spot may attract them, but they are highly localized and do not travel far.

Both the adults and larvae feed almost exclusively on the leaves of the Tansy plant, though they are known to occasionally use Water Mint and Gypsywort in wetland areas.

No, they are considered 'Nationally Rare' in many regions and are usually restricted to specific riverbank and fenland habitats rather than typical suburban gardens.

Tansy Beetles are slightly larger and have a more golden/copper sheen compared to the bright, pure green of the Mint Beetle; additionally, Tansy Beetles are primarily found on Tansy plants rather than garden mint.

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