The Baltimore checkerspot has three distinct life stages, each with their own appearance. As a caterpillar, the Baltimore checkerspot has a black head and a body covered in alternating bands of black and bright yellow lines, with spine-like protrusions arranged along the alternating bands. As a pupa, the Baltimore checkerspot has a white chrysalis with bright orange-yellow and black markings.
The adult Baltimore checkerspot butterfly has four wings with a black base with orange spots and two broad, banded borders, with the inner one showing checkers in white and the outer one in orange to yellowish-orange. Their wingspan is about 2.5 inches.
Baltimore checkerspot caterpillars start feeding on white turtlehead in the summer when the caterpillars are small. As they grow, Baltimore checkerspot caterpillars use a variety of host plants in addition to turtlehead, including arrowwood viburnum, narrow-leaved plantain, penstemon and honeysuckle.
Adult Baltimore checkerspots feed on nectar from flowering plants that bloom during their flight period, such as milkweeds, dogbane, several species of mountain mint, wild rose and wild blackberry.
As caterpillars, the Baltimore checkerspot suffers high mortality from falling off host plants and from parasitism by wasps. To combat these predators, newly-hatched caterpillars build a communal web at the end of their host plants’ leaves where they’re more protected from parasitic wasps.
Once a butterfly, however, the Baltimore checkerspot is poisonous and bad tasting. They advertise these adaptations to predators like birds by spreading their brightly-colored wings while feeding on nectar.
The flight pattern on Baltimore checkerspots is fast and erratic. While in flight, it’s bright wings can dull and black.
Reproduction and Life Cycle
The life cycle of Baltimore checkerspots begin in early summer when male adults perch near the ground to find females. After mating, female butterflies lay one brood of 100 to 700 eggs under the leaves of white turtlehead, the Baltimore checkerspot’s larval host plant.
Eggs start out yellow and change to red over a period of about 20 days, when they hatch into tiny caterpillars. Newly-hatched caterpillars move to the tip of the plant and feed together in a web which is enlarged downward as the caterpillars consume more of the plant. The caterpillars will continue to eat, grow and molt throughout the summer.
Once it starts to get colder, they hibernate in dead leaves and grass on the ground until the weather warms in mid-April and the caterpillars become active and resume feeding. Baltimore checkerspot caterpillars then form a chrysalis and start their two-week transformation into butterflies. Once the adult butterflies emerges, the cycle repeats.
Did You Know?
- The Baltimore checkerspot is named for George Calvert, the first Lord Baltimore, because its orange and black colors match those on his heraldic shield.
- The Baltimore checkerspot has been the official insect of Maryland since 1973.
- The Baltimore checkerspot is in the family Nymphalidae, also called the brush-footed butterflies due to their reduced front legs. This trait makes them appear to have four legs instead of six.
- Today, wild colonies are known from approximately 20 sites in 8 counties. These colonies occur in the western and central portions of Maryland including the Appalachian Plateau, the Blue Ridge, the Ridge and Valley Region and in the Piedmont.
Sources and Additional Information
- Protecting Maryland's State Insect: Introducing the Baltimore Checkerspot Recovery Team - Maryland Department of Natural Resources
- Baltimore Checkerspot - Mass Audubon
- Baltimore Checkerspot Euphydryas phaeton - Butterflies and Moths of North America
- Rare, Threatened and Endangered Animal Fact Sheet: Baltimore Checkerspot - Maryland Department of Natural Resources
- Baltimore Checkerspot - Butterfly Identification
- Conservation and Management of the Baltimore Checkerspot (Euphydryas phaeton Drury) in Maryland - Maryland Department of Natural Resources