Invertebrates
Baltimore Checkerspot
Euphydryas phaeton · also called Baltimore checkerspots
Clustered together within a silk web spun onto a turtlehead plant, a group of young Baltimore checkerspot caterpillars prepares to overwinter as a partially grown group, their survival tied closely to a single wetland plant most people walk past without a second glance.
Overview
The Baltimore checkerspot, Euphydryas phaeton, is a boldly patterned butterfly native to wetland and adjacent grassland habitat across a range spanning the northeastern and midwestern United States. Its strong historical dependence on turtlehead as a caterpillar host plant, communal web-spinning caterpillar behaviour, and habit of overwintering as a partially grown larva make it one of the more ecologically specific and behaviourally distinctive butterflies in eastern North America.
A butterfly tied to one wetland plant
The Baltimore checkerspot’s entire early life cycle revolves around turtlehead, a single wetland plant whose presence or absence can determine whether a stretch of habitat can support the species at all.
Status
Least Concern, present across suitable wetland habitat throughout the northeastern and midwestern United States, though declining locally where wetland habitat containing turtlehead has been lost.
Baltimore Checkerspot: common questions
Why does the Baltimore checkerspot depend on turtlehead?
This species' young caterpillars feed heavily on turtlehead, a wetland plant, and this close historical association has shaped much of the species' life cycle, including its need for wetland habitat where turtlehead grows, even though older caterpillars can also feed on several other wetland and grassland plants later in development.
Why do Baltimore checkerspot caterpillars live in groups?
This species' caterpillars spin a communal silk web directly onto their turtlehead host plant and shelter together within it through the fall, a group living strategy that may offer some protection from predators and help the caterpillars survive together through the challenges of the coming winter.
How does the Baltimore checkerspot survive winter?
This species overwinters as a partially grown caterpillar rather than as an egg, adult, or chrysalis, entering a dormant state to survive the cold months before resuming feeding and completing its development the following spring once temperatures warm sufficiently.
Why has the Baltimore checkerspot declined in parts of its range?
This species depends on wetland habitat containing its turtlehead host plant, and as this specific wetland habitat has been lost or degraded in parts of the northeastern and midwestern United States, suitable conditions for the species have become more limited, contributing to localised population declines.