Graffiti for Butterflies

Directing monarch butterflies to urban food sources along migratory routes in North America.

GFB uses images of milkweed flowers to broadcast the location of food sources to monarch butterflies. In the above prototype, the graffiti is placed on a wall above an actual milkweed plant in New York City, signaling the presence of nectar to hungry monarchs in the vicinity.

Monarchs regularly pass through wide swathes of human settlement as they migrate each year between wintering sites in Mexico and summering grounds in the United States and Canada. GFB is the equivalent of a fast-food sign on a highway, advertising rest stops (waystations) to monarchs traveling through the area.

ultraviolet uv graffiti spray paint spraypaint

Milkweed flowers have natural ultraviolet (UV) patterns that are recognizable to monarch butterflies. These patterns are invisible to us because we can’t see light in the ultraviolet spectrum. GFB uses sunblock to paint the graffiti in a way that mimics these natural ultraviolet properties. (Sunblock is perfect for this, because it’s designed to reflect ultraviolet light away from our UV-sensitive bodies— it’s essentially a cheap and easy UV spray paint.)

The head (corona) of the graffiti flower is sprayed with sunblock to produce a burst of color in the ultraviolet spectrum. The above video is a simulation of monarch butterfly vision— it’s not possible to accurately represent the color of ultraviolet light in the spectrum visible to humans.

Milkweed leaves are the monarch caterpillar’s sole food source. In this video, a monarch visits a balcony in New York City. It feeds and lays eggs, later hatching into tiny hungry caterpillars.

Marisa Olson’s review of Graffiti for Butterflies at Rhizome:

The Metafilter comment thread on this project can be found at:

BLDG Blog covers the project at:

  • Dr. Ronald Rutowski
    April 28, 2009 10:09 pm

    Here are a couple of my thoughts stimulated by this idea.

    1) Many flowers vary across the surface of the petals in how much UV light they reflect. The resulting patterns are invisible to our naked eye, but most nectar feeding insects can see them. This means that different parts of the flowers are perceived by insects as being different colors, and insects do use these UV patterns to recognize and orient to flowers. Do milkweed flowers have such UV patterns as is claimed on this page? I could not find any images on the web to confirm this and none is provided on the web page.

    2) Contrary to what is suggested on this web page, sunscreen works by absorbing, not reflecting, UV. Chemicals in the sunscreen absorb UV light thereby preventing it from reaching and burning our skin. Making a sign or coating a flower with sunscreen would make a surface that would reflect very, very little UV, which would also change its color to an insect.

  • Bob Hovey
    March 9, 2015 7:52 pm

    Actually, it depends on the sunscreen…

    Physical sunscreens use inorganic chemicals like zinc oxide or titanium oxide to reflect or scatter ultraviolet radiation. Organic sunscreens use ingredients like octyl methoxycinnamate (OMC) or oxybenzone absorb UV radiation, dissipating it as heat. Most sunscreens combine inorganics and organics. Here’s why…

    UV rays consist of UVB and UVA photons. The shorter wavelength UVB rays don’t penetrate deeply into skin; they are the primary cause of sunburn and skin cancer. UVA rays penetrate the deeper layers of skin, where they produce free radicals. UVA exposure has been linked to premature aging of the skin and immunologic problems.

    Because sunburn is primarily a UVB effect, it is possible for a sunscreen product to deliver high SPF while allowing a significant percentage of UVA photons to reach the skin. To deliver true broad spectrum protection, products must also block a significant fraction of the UVA photons. Therefore, most sunblocks sold in the US contain significant levels of zinc oxide, avobenzone or titanium dioxide… which do reflect UV.

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