Karner blue butterflies depend on a single food source for their survival: wild lupine (Lupinus perennis). This wildflower grows in sandy soils, sandy pine barrens, beach dunes and oak savannahs.
The Karner blue butterfly (Plebejus samuelis) occurs in areas with wild lupine, the plant their caterpillars depend on. They rarely wander far from where they hatched, typically staying within 300 to 600 feet of their home area. They are roughly the size of a Canadian quarter, with a wingspan of about 2.2 cm. They are distinguished by what you see on the undersides of their wings: distinctive orange crescents that frame rows of black spots against a light silver-gray background.
Both males and females are the same size and have the diagnostic orange crescents on the wing undersides. What separates them is males have a deep sky blue color across the upper surfaces of their wings, bordered by narrow black margins and edged with a white fringe. Females display a darker blue near the body to grayish-brown toward the edges.
• Eastern tailed-blue (Everes comyntas)
• Spring azure (Celastrina argiolus complex)
• Summer azure (Celastrina neglecta)
• European/common blue (Polyommatus icarus)(non-native)
The Karner blue’s entire existence is timed to the wild lupine’s growing season. Females lay tiny eggs directly on or near the lupine plants in early summer. There are two generations of adults per year: first-generation eggs hatch around early April after overwintering as eggs, then hatch into adults. These adults lay eggs that will hatch after about a week and turn into caterpillars, and eventually turn into the second-generation of butterflies. The second-generation butterflies will also lay eggs, but those eggs won’t hatch until the following spring. Eggs hatch within 7 to 8 days of being laid and are immediately independent. The tiny, bright green or whitish-green caterpillars immediately begin feeding on lupine leaves and leave behind “windowpanes” – transparent leaf skeletons where they’ve consumed everything except the vein structure. The total development from egg through caterpillar stage and into the pupal form typically takes 25 to 60 days, depending on temperature and conditions. Around mid-May (for the first generation), caterpillars form a chrysalis; a bright green pupal case that hardens and changes to light tan with hints of purple just before the butterfly emerges. The butterfly must rest for about 45 minutes after emerging, expanding and drying its wings before it’s ready to fly. The adults typically only live up to 5 to 7 days in the wild with some lasting up to 2 weeks. Their entire life cycle takes roughly 2 to 3 months.
Le rétablissement du bleu mélissa en Ontario nécessitera la réintroduction de ce papillon dans son aire de répartition historique. Cependant, avant que cela ne soit possible, l'habitat de savane à chênes et de prairie à herbes hautes dont l'espèce dépend doit être restauré, géré et évalué pour s'assurer qu'il peut supporter une population de bleus mélissa autosuffisante.
If you live in Karner range and own land, consider restoring wild lupine and managing your property with prescribed fire or mechanical clearing to keep it open. Even small patches help. Support conservation organizations working on habitat restoration and reintroduction. Avoid pesticides, which harm butterflies and their food plants. If you encounter a Karner blue, report your sighting to your province’s wildlife agency. Finally, learn to identify this butterfly and teach others; the more people who recognize and appreciate them, the more support conservation efforts receive.
Q: Why is the Karner blue butterfly so rare now?
A: The primary culprit is fire suppression. For millennia, lightning fires burned oak savannas and pine barrens regularly, keeping them open and sunny. Cultural burning by Indigenous communities supported this habitat too. When European settlers arrived, they suppressed these fires to protect property. Without fire, forests gradually closed over the savannas, lupines couldn’t survive in the shade, and Karner blues disappeared. Agricultural development, residential sprawl, and pesticide use have made the situation worse.
Q: Could the Karner blue adapt to other plants besides lupine?
A: Not really. The Karner blue’s caterpillars are obligate lupine feeders; they cannot digest other plants, even closely related ones in the pea family. This extreme specialization makes them vulnerable but also means conserving lupine automatically conserves the butterfly.
Q: Are the ants harming the Karner blue caterpillars or just stealing sugary secretions?
A: The relationship is genuinely mutualistic. Ants provide real protection against parasitic wasps and predatory insects, increasing caterpillar survival substantially. In exchange, they harvest the sugary secretions. It’s a win-win arrangement millions of years in the making.
Q: Can Karner blues be bred in captivity?
A: Yes, several institutions have successfully reared Karner blues through complete life cycles in captivity. These include but are not limited to: Toledo Zoo (Ohio), U.S. Fish and Wildlife Service (New Hampshire programs), and Albany Pine Bush Preserve Commission in (New York).