Marsh Fritillary: a two-minute wildlife lesson

Butterflies of Europe · day 1 of 7

Five facts

1. A female can lay up to 350 eggs in one batch. The eggs change colour as they develop: yellow, then crimson, then dark grey before hatching.
2. The caterpillars live together in a silk web spun around their food plant, and they spend the whole winter sheltered inside it.
3. In spring, the caterpillars sunbathe. Soaking up the sun's heat warms their bodies, which helps them grow faster even when the air is cool.
4. Mothers are picky. Studies suggest they look for the greenest, healthiest leaves to lay their eggs on.
5. After many months as a caterpillar, the adult butterfly lives a short life, usually about two weeks.

The quiz

1. What colour are marsh fritillary eggs just before they hatch?

• Bright green
• Dark grey (correct)
• Pure white
• Sky blue

They go from yellow to crimson and finally dark grey just before hatching.

2. Where do the caterpillars spend the winter?

• Each one alone, deep underground
• Under the bark of trees
• Together inside a silk web (correct)
• As adult butterflies in caves

They hibernate together inside a web built around their host plant.

3. Why do the caterpillars bask in the sun in spring?

• To warm up and grow faster (correct)
• To dry out their web
• To attract birds
• To find a mate

The sun's heat raises their body temperature, which speeds up their development.

4. Which leaves do females seek out for their eggs?

• The driest
• The smallest
• The yellowest
• The greenest (correct)

Females use their eyes to find the greenest leaves.

5. How long does an adult marsh fritillary usually live?

• One day
• Six months
• About two weeks (correct)
• Two years

Adults have short lives, usually about two weeks.

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