Butterfly Pupae in Living Color

by jjneal

Butterfly collectors have known for over a century that the background color of the environment can affect the color of the chrysalis (pupa) of some species of butterfly. The Black Swallowtail butterfly, Papilo polyxenes, has a range of color morphs from light green to dark brown. On green foliage, the pupa is a light green color. On dark stems (often in the fall) the pupae are brown. The color variation helps the pupa better blend into the environment and provides some measure of protection from predators.

How does the Black Swallowtail know how to match the color of its pupa to the environment? Caterpillars have photo receptors (stemmata) with pigments that presumably can detect the surrounding color when it starts to pupate. The color triggers or inhibits the release of a hormone that controls pupal coloration. High levels of hormone will produce a brown pupa, low levels produce a green pupa. Injection of caterpillars on a green background with a nerve extract from caterpillars that are on a brown background will produce brown pupae.

Adjusting their color so they are harder to detect helps Black Swallowtail pupae avoid predation.

Green Form of the Black Swallowtail Chrysalis

About jjneal

Jonathan Neal is an Associate Professor of Entomology at Purdue University and author of the textbook, Living With Insects (2010). This blog is a forum to communicate about the intersection of insects with people and policy. This is a personal blog. The opinions and materials posted here are those of the author and are in no way connected with those of my employer.
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7 Responses to Butterfly Pupae in Living Color

  1. Scheky says:

    This image shows a green/yellow pupae on a brown background. This contradicts the stemmata sensing hypothesis. I’m guessing that this pupae was being kept as a ‘pet’ and the brown leaf was an artifact from the leaf drying out indoors prior to a natural plant senescence.

  2. David Stone says:

    Questions: Has the nature/chemistry of pupal color been worked out yet? For example, is the color a result of pigment deposition rather than “structural” coloration via interference? If the green color is due to a green pigment, is that pigment synthesized by the caterpillar/pupa or might it be recycled chlorophyll(s) from the food plant? Where is the pigment located–is it deposited as a separate layer, or it is intermixed with the chitin? Thank you.

    • jjneal says:

      It depends on the species. Some pupae are clear, such as the monarch and you can see adult colors through the thin chrysalis. Most are pigments. Very few are investigated. What we know about color in insects comes from relatively few studies of a several dozen species.

  3. jjneal says:

    There are papers that summarize much of what is known. Eye pigments are the most studied pigments.
    This review has a summary table of pigment classes
    http://search.proquest.com/docview/1530099023/fulltextPDF/280BFA391E4FEEPQ/1?accountid=13360

  4. Fathima mufeedha.k says:

    found a common Mormon pupa on the lemon plant. it has been more than 15 days in the pupa stage. not yet emerged, pupa is a brown shade

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