Baltimore Checkerspot Butterfly

The Baltimore Checkerspot gets its name from the orange and black colors of the heraldic shield of George Calvert who was the first Lord Baltimore. It's also the state insect of Maryland.

The range of these butterflies is very local, and some populations are thought to be declining. As the Baltimore Checkerspot prefers wetland habitats, the loss and degradation of these habitats is causing significant declines in Checkerspot populations and other beloved species.

The most common host plant for Checkerspots is the White Turtlehead (Chelone glabra) which also contains a defense opportunity. White Turtlehead contains chemicals called iridoid glycosides, so when the Checkerspot feeds on this plant, they become bad tasting to birds. As habitat shrinks, the Baltimore Checkerspot has had to expand its host plant preferences to include English Plantain (Plantago lanceolata), which grows in dry fields. It's been observed that in some regions where English Plantains grow, the Baltimore Checkerspot is found in massive concentrations.

In adulthood, the Checkerspots nectar on Common Milkweed (Asclepias syriaca) and Spreading Dogbane (Apocynum androsaemifolium), another plant that is toxic to humans, dogs, livestock, and some other mammals but not for the Checkerspot. In fact, milkweeds and dogbanes are closely related!

The Baltimore Checkerspot is univoltine, meaning that it only has one brood per year. In its southern range, the brood flies from May to June and in the northern range, the brood flies from July to August. Univoltine species often evolve to coincide their life cycles with the host plant they depend on. This life history strategy makes this butterfly species at a higher risk for population declines due to their specific requirements.

Additional Resources

• Adirondacks Forever Wild - Baltimore Checkerspot (Euphydryas phaeton)
• Conservation and Management of the Baltimore Checkerspot (Euphydryas phaeton Drury) in Maryland: Strategies for Statewide Monitoring and for Wetland Restoration, Captive Breeding and Release in the Piedmont Region
• Butterflies and Moths of North America - Baltimore Checkerspot
• Plant of the Week: Spreading Dogbane (Apocynum androsaemifolium)