THE ANIMAL FILES

Monarch butterfly

Danaus plexippus

One migration route can take more than one generation to complete.

Monarch butterflies develop through egg, caterpillar, pupa and adult stages. In the well-studied North American migration, successive generations carry the northward journey forward, while the pupal transformation turns a leaf-eating larva into a flying adult.[1]

Follow the evidence ↓
Monarch butterfly
Image: Didier Descouens · Commons · CC BY-SA 4.0
Development
Complete metamorphosis[1]
Pupation
The caterpillar hangs from a silk attachment[1]
Migration
Some routes span several generations[1]

The hanging caterpillar becomes the chrysalis

Before pupation, the caterpillar makes a silk attachment and hangs in a curved J shape. It then sheds its larval skin, revealing the developing green chrysalis. The chrysalis is a new developmental stage exposed by moulting, not a separate leaf wrapped around the caterpillar.[1]

An adult forms inside

The newly exposed chrysalis is initially soft and changes shape as it firms. Later, the developing adult’s dark and orange pattern becomes visible before emergence. The apparently still stage therefore includes major structural development rather than a pause with an unchanged caterpillar waiting inside.[1]

A journey passed between generations

In eastern North America, overwintering adults can move north in spring and reproduce before later generations continue farther north. The returning autumn generation and the whole annual population route are not identical to one individual making every leg. Other monarch populations do not follow this same migratory pattern.[1]

A COMMON MIX-UP

Does one monarch complete every part of the annual migration?

Not in the multi-generational route described here. Adults reproduce along the way and descendants continue the journey, so a population itinerary can outlast the individuals that began it.[1]

TRY A LITTLE REASONING

Why distinguish an individual track from a population route?

Reveal the explanation

A tagged butterfly documents its own movement, while the annual route includes different generations. Combining them without distinguishing the scales could falsely assign several animals’ journeys to a single insect.[1]

Sources & editorial notes

Adapted and translated from the cited Wikipedia revisions, with source-linked reasoning. Image credit and licence are listed separately above.

Adapted and translated from Wikipedia contributors; exact revisions are linked below. CC BY-SA 4.0

  1. Wikipedia contributors — Monarch butterfly (fixed revision; adapted and translated)
  2. NCBI Taxonomy — Danaus plexippus (identity and classification)

Last fact check:

One discovery leads to another

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