Long ago, when plants began exploiting animals to carry pollen between flowers, they encountered butterflies. Butterfly adults fed mainly on sugar water (nectar). Flowers adapted to this by offering little cups of nectar, positioned so that a feeding butterfly would get pollen on itself--on the proboscis or face or wings, depending on the flower--which then pollinated the next flower of the same species when the butterfly moved to find more nectar there. I said "exploit" but for most flowers and butterflies it is a reasonable trade, pollen movement for food, making butterflies a major group of pollinators.
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| swallowtail butterfly on mint flowers |
Butterflies are grouped into a superfamily within the order Lepidoptera. Other Lepidoptera are moths, very numerous and diverse, and skippers, which look like double-winged butterflies. Like all Lepidoptera, butterflies begin as eggs. The eggs hatch into larvae (caterpillars) that eat ravenously for a week or two, shedding their exoskeleton four or five times as they outgrow it, then forming a pupa in which radical metamorphosis occurs. After a few days to more than a year, depending on the butterfly species, winged adult butterflies emerge from the pupa. These mate and lay more eggs. With a few exceptions, adult butterflies feed only on nectar (sugar water) found in flowers. Adults rarely live more than a few weeks. (There are 15,000 species of butterflies, so there are exceptions to every generalization).
Butterflies differ from moths by their scientific classification, but generally obvious differences are that butterflies fly by day and moths fly at night, butterflies hold their wings vertically when sitting compared to flat or otherwise folded for moths, the antennae of butterflies are narrow and straight while moths often have broad, feathery antennae. Finally many butterflies are bright colored and most moths are drably colored (camouflaged).
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| Butterfly (aphrodite fritillary?) on coreopsis (Coreopsis) |
As day-flying animals, butterflies have good eyesight, seeing at least all the colors humans see and also into the ultraviolet, which is invisible to us. In response, flowers for butterflies tend to be bright colored--red, orange, yellow, white, blue, purple, just not black, brown or green--so they are easy for butterflies to see against leaves and branches. Butterflies fly conspicuously to and from flowers, preferring flowers that stick up above the foliage or hang well below it. Partly they take advantage of sunlight to warm their bodies and watch for predators. Partly, maneuvering with wings longer than your body isn't simple; flowers where nothing bumps or tangles the wings are a whole lot easier to feed at.
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| battered silver-bordered fritillary butterfly on an aster |
Butterflies fly well enough that they can hover at a flower, but mostly they land, standing to probe into the flower for nectar with their proboscis. Thus, many butterfly-adapted flowers offer a steady surface to stand on, sometimes horizontal, sometimes vertical. Anthers holding the pollen may bump the butterfly on the face as it reaches in to get nectar, stick the nectar on the sides of the proboscis in the chamber leading to the nectar or curl around to spread pollen on the back of the butterfly's head as it feeds.
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| Small speedwell flowers (no butterflies visible) |
Butterflies generally are not interested in pollen. They do not collect it or eat it except accidentally. (With a few notable exceptions).
Flowers of most colors, from red to yellow to blue and purple, attract butterflies. To get their attention from far away, plants often mass their flowers, putting many small flowers together for a greater visual impact.
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| multiple chokecherry (Prunus) flowers, dramatic against the green leaves |
Many butterflies are quite wary, moving and dodging at the first shadow that might be a hungry bird. In a patch of flowers, for example the red Indian paintbrushes (Castilleja) scattered in the mountain meadow below, this works very well for the plants because, after being disturbed, the butterfly is likely land on a different plant and, by feeding there, pollinate.
Some butterflies are local, overwintering in the ground, living out their lives in one small area. Others will disperse hundreds of miles from their birthplaces or take part in an annual migration. In all cases adult butterflies need lots of nectar from flowers. And they need food from early in the spring when the first butterfly emerges as an adult until late fall when the last ones migrate south or are killed by frost.
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| tropical swallowtail on Stachytarpheta flower |
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| Butterfly on Lantana flowers that stick out above the leaves |
Larval butterflies have a very narrow diet; for example monarchs (Danaus plexippus) eat only species of milkweed (Asclepias species). Adult butterflies, however, are quite opportunistic. Butterfly adults feed on flowers if they can reach the nectar and it tastes good, whether the plant is native or introduced from another continent, wild or improved by plant breeders.
Some of the flowers that appeal to humans have accidentally made them uninteresting to butterflies, for example when the extra petals of a double marigold block access to the nectar, or if the color (nearly black) doesn't appeal to them. These are exceptions however, most butterflies like the same colors people do. (A swallowtail circled me in my backyard and I realized it thought my bright blue shirt might be a flower. Oops, sorry.)
In summary, flowers that attract butterflies tend to be bright-colored, open all day, in warm open locations, and easy for butterflies to reach into and feed on.
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| Butterfly on marigold flowers |
Comments and corrections welcome.
Note: I tried to identify the plants and butterflies. I have an educated guess on the plants in the photos. The butterflies too often stumped me. If you recognize butterflies, my photos are from the Colorado Front Range, except for the dark swallowtail on Stachytarpheta photo and the photo below that with Lantana. The swallowtail was probably in a Florida butterfly garden, the Lantana photo was taken in Costa Rica. My photos run to big butterflies because they are easier to photograph well. Watch small butterflies if you get a chance.
References
Gaskell, M. 2023. A different light. Lady Bird Johnson Wildflower Center. link (Accessed 12/1/24).
Proctor, M., P. Yeo, and A. Lack. 1996. The Natural History of Pollination. Timber Press. Portland, OR.
Rechner, M. 2023. Butterflies vs moths. What are the differences. Brandywine Conservancy. link (Accessed 12/1/24).
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