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Silver-studded Blue
Insects diurnal

Silver-studded Blue

Plebejus argus

A shimmering jewel of the heathland, the Silver-studded Blue is a tiny marvel with a secret. Beyond its iridescent wings lies a fascinating alliance with ants that helps this delicate species thrive in rugged landscapes.

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Quick Identification

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Size

Wingspan of 25–31 mm (approx. 1.0–1.2 inches)

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Colors

Males are iridescent violet-blue with thick black borders; females are primarily chocolate-brown with orange crescents; both have silver-studded spots on the underwing.

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Key Features

  • Metallic silver-blue 'studs' on the underside of the hindwings
  • Males have vibrant blue upper wings with a broad black border
  • White fringe along the wing edges
  • Low, fluttering flight pattern usually close to the ground

When You’ll See Them

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Activity pattern diurnal
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Peak hours 10:00 AM - 4:00 PM
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Season Late June to mid-August
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Diet Adults feed on nectar from heather, bird's-foot trefoil, and wild thyme. Larvae eat the young shoots and flowers of gorse, broom, and various heathers.
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Habitat Lowland heathlands, sand dunes, and occasionally limestone grasslands with short vegetation.

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Behavior

The Silver-studded Blue is famous for its mutualistic relationship with ants, specifically species like Lasius niger. The ants protect the butterfly's larvae and pupae from predators; in return, the caterpillars provide the ants with a sugary secretion. This bond is so strong that females often use the presence of ant nests as a primary indicator of where to lay their eggs.

These butterflies are highly colonial and sedentary, often spending their entire lives within a 20-meter radius of where they hatched. They are most active during the warmest parts of the day, frequently seen basking on low-lying vegetation with their wings spread to capture solar heat. At night or during cloudy weather, they can be found roosting upside down on grass stems or heather.

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Camera Tips

To successfully capture the Silver-studded Blue on a backyard or trail camera, focus on 'micro-habitat' placement. These butterflies are rarely found more than a few inches off the ground, so your camera should be mounted very low—ideally 6 to 10 inches high—aimed at a cluster of Bell Heather or Bird's-foot Trefoil. Using a macro lens attachment or ensuring your camera has a close-focusing distance of at least 15-20cm is critical for capturing the fine details of the 'silver studs' on their wings.

Since these butterflies are highly sensitive to temperature, position your camera in a south-facing, sheltered 'sun trap.' Look for sandy patches of soil or short-grazed turf where you see ant activity, as the butterflies will likely congregate there to bask or lay eggs. If your camera has a time-lapse mode, set it to trigger every 30 seconds during peak sunny hours (11 AM to 2 PM) to catch them as they rotate their wings to track the sun.

Lighting is the most important factor for making the blue scales 'pop.' Try to angle the camera so the sun is behind you or slightly to the side; this prevents the reflective scales from washing out while still illuminating the iridescent violet-blue of the males. If your camera allows for manual shutter speed settings, keep it fast (1/500 or higher) to freeze the motion of their rapid wing-flicks, which they use to signal to other butterflies or deter small predators.

Similar Species

Species that look similar or are commonly confused with Silver-studded Blue.

Common Blue

Lacks the metallic silver studs on the underwing and has a thinner black border on the male's upper wings.

Adonis Blue

Displays a much brighter, 'electric' blue and has black lines crossing the white wing fringes.

Frequently Asked Questions

They are strictly diurnal and most active during full sun between 10:00 AM and 4:00 PM. On overcast days, they remain inactive, often resting head-down on grass stems.
The best way to attract them is by planting their preferred nectar sources like Bird's-foot Trefoil, Bell Heather, and Wild Thyme. Providing a sunny, sheltered spot with some bare sandy soil can also encourage them to visit.
Adults drink nectar from low-growing wildflowers. The caterpillars have a broader diet, munching on the leaves and flowers of gorse, broom, and various types of heather.
No, they are quite rare in standard suburban gardens as they require specific heathland or limestone grassland habitats. However, if your home borders a nature reserve or heath, they may drift into your yard.
The key is the underside of the wing. Silver-studded Blues have distinct metallic, light-reflecting 'studs' inside the black spots on their hindwings, which the Common Blue lacks. Additionally, the male Silver-studded Blue has a much thicker black border on the upper wing.

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