Wild Facts About The Common Buckeye Butterfly

How To Identify Common Buckeye Butterflies

Appearance Of Adult Common Buckeye Butterflies

Wingspan: 2.0 – 2.5 inches (5.0 – 63.4 cm)
Males and females look similar.
- Females tend to be slightly larger and have larger wing markings (Daniels 2003).
Above:
- Both forewings and hind wings are brown overall.
- Each forewing has two short, wide, orange wing bars and a single large, multi-colored eye spot.
- Each hind wing has two large, multi-colored eye spots—one very large, one slightly smaller.
  - A series of concentric rings form patterns that look like large eyes.
  - The eye spots are multi-colored in rust, creamy white, lavender, and velvety black.
  - The eye spots include a spot of white that mimics the shine of light reflecting off a moist eyeball.
- Hind wing margins are orange, with black and tan stripes along the edges.

Common Buckeye Butterfly. Junonia coenia. Diagram labelled with identifying marks. Brown butterfly. Insect. Photograph and design created by the author. Copyright © 2025 Now I Wonder. All rights reserved. — Common Buckeye Butterfly Junonia coenia Diagram labelled with identifying marks Brown butterfly Insect Photograph and design created by the author Copyright © 2025 Now I Wonder All rights reserved

Below:
- The appearance of these brown butterflies varies varies by season.
- The forewing and hind wings of spring adults are brown; the wings of fall adults are rust.
- The upper wing surface is deep brown and orange while the under surface is more muted in shades of tan and rust.
- On some individuals, wing spots show on both surfaces, with muted color on the under surface. On other individuals, the wing spots are small, dark, and subtle.

Appearance Of Common Buckeye Caterpillars

Common Buckeye caterpillars vary in color but are usually mostly black with white or orange along the sides.
They grow to approximately 1.8 inches) (4.5 cm) and have:
- Metallic blue-black spines,
  - The bases from which these spines sprout are black on top and orange on the sides,
- A pale stripe that runs lengthwise down their backs,
- Orange and black heads,
- Orange prolegs
Common Buckeye caterpillars resemble the larvae of two other, closely related Buckeye species that overlap in southern Florida and Texas:
- Mangrove Buckeye (Junonia evarete),
- Tropical Buckeye (Junonia genoveva) (Wagner 2005).

Common Buckeye Butterfly. Junonia coenia. Brown butterfly. Insect. Photograph taken by the author. Copyright © 2025 Now I Wonder. All rights reserved. — Common Buckeye Butterfly Junonia coenia Brown butterfly Insect Photograph taken by the author Copyright © 2025 Now I Wonder All rights reserved

How to Find Common Buckeye Butterflies

Flight Season: Adults fly between April through November in North Carolina.
- Common Buckeye butterflies can’t withstand freezing temperatures, so northern individuals fly south in the fall.
- Some may overwinter in North Carolina during exceptionally warm winters but most of the time, these brown butterflies spend the winter months in the Gulf Coast states, like Florida (Daniels 2003).
Look for Common Buckeye butterflies in open, disturbed areas, like along roadsides and in power line cuts, old fields, and gardens.
- These brown butterflies seem to like the edges of pine woods as well.
Adult Common Buckeye butterflies feed on nectar from a variety of flowering plants. They especially like nectar from plants in the Aster family (Asteraceae), like Tickseed (Bidens aristosa) (Opler 1994) and Greater Tickseed (Coreopsis major).
Male Common Buckeye butterflies are territorial and often fly out to meet moving objects. This trait—along with a liking for perching on bare ground—helps make these brown butterflies easy to observe from a distance. However, they are wary and likely to fly off when approached.

Two male Common Buckeye Butterflies fighting for territory. Junonia coenia. Brown butterfly. Insect. Photograph taken by the author. Copyright © 2025 Now I Wonder. All rights reserved. — Two male Common Buckeye Butterflies fighting for territory Junonia coenia Brown butterfly Insect Photograph taken by the author Copyright © 2025 Now I Wonder All rights reserved

Common Buckeye Butterflies Are Toxic Chemical Specialists

As adults, Common Buckeye Butterflies feed on nectar, but the caterpillars are herbivores that chew plant leaves.
Common Buckeye caterpillars feed on plants that produce defensive chemicals called “iridoid glycosides”, such as those in the Plantago genus (Plantain family Plantaginaceae).
- While these toxins deter some generalist herbivores, Common Buckeye caterpillars specialize on eating leaves that contain iridoid glycosides.
Common Buckeye caterpillars sequester the toxic chemicals into their own body tissues for defense against predators.
Because Common Buckeye caterpillars are iridoid glycoside-feeding specialists, they sequester these toxins more efficiently than other butterfly species.
- One study found that Common Buckeye caterpillars sequestered from three to seven times the amounts sequestered by two generalist species, the Agreeable Tiger Moth (Spilosoma congrua) and the Salt Marsh Moth (Estigmene acrea).
  - The Common Buckeye caterpillars sequestered from 5 to 15% dry weight iridoid glycosides compared to:
    - Agreeable Tiger Moth sequestered only 3 to 6% dry weight,
    - Salt Marsh Moth sequestered around 2% (Lampert and Bowers 2010, https://doi.org/10.1007/s10886-010-9849-4).

Being Toxic Helps Only To A Point

The chemical defense Common Buckeye caterpillars obtain by feeding on iridoid glycoside-producing plants and sequestering those toxic chemicals in their bodies is not infallible.
- First, some plants manufacture more, more potent, and/or different iridoid glycosides than other species so vary in the amount and effectiveness of defensive chemicals available to the feeding caterpillars.
  - For example, Plantago lanceolata contains two types of iridoid glycosides, aucubin and catalpol, while Plantago major contains only aucubin.
  - Caterpillars are generally sedentary so “take what they can get” as they feed on the plants upon which they hatched.
- Second, some predators are adept at bypassing the toxic chemicals, are unaffected by the chemicals, and/or fail to associate certain prey as being unpalatable.

Killed, But Not Necessarily Eaten

For example, the Carolina Wolf Spider (also called the Giant Wolf Spider, Hogna carolinensis) is both the largest wolf spider species in North America and a major invertebrate predator of Common Buckeye caterpillars.
A study that researched the effects of iridoid glycoside sequestration on the predatory behavior of Carolina Wolf Spiders found that:
- The spiders attacked and rejected more Common Buckeye caterpillar larvae raised on P. lanceolata (i.e. larvae containing high levels of iridoid glycosides) than larvae raised on P. major (i.e. larvae containing low levels).
  - Caterpillars reared on both plant types often had droplets of hemolymph where the spiders had bitten them and some regurgitated or defecated on the spiders’ mouthparts after being grabbed.
    - Spiders rejected those caterpillars who had fed on P. lanceolata and who regurgitated or defecated on the spiders’ mouthparts quickly and universally (six of six times).
- However, the spiders attacked equal numbers of both types of caterpillar prey and did not seem to learn to avoid the unpalatable, high iridoid-containing caterpillars (Theodoratus and Bowers 1999, https://doi.org/10.1023/A:1020894729188).
So, toxicity may prevent the caterpillars from being eaten but doesn’t stop them from being killed.

Adult Common Buckeye Butterflies Reward Themselves

Common Buckeye butterflies feed on flower nectar and can discriminate between flowers by the amount of available nectar offered by each.
- While the flowering plants upon which butterflies feed lose their nectar, they benefit from the butterflies’ visits as the insects help pollinate the plants.
The flowers of some plants change color over time and flower color can sometimes indicate nectar volume to pollinators such as Common Buckeye butterflies.
- The flowers of at least 214 genera across 74 families and 33 orders of flowering plants worldwide change color.
- For example, the flowers of Common Lantana (Lantana camara) are yellow on the day the buds open, then turn to orange and then red over time.
  - Only the yellow flowers offer nectar to butterflies like the Common Buckeye.
- A study that offered Common Buckeye and Gulf Fritillary butterflies choices between L. camara flowers with different visual characteristics found that:
  - The butterflies chose to visit larger displays of flowers over smaller displays, regardless of the nectar reward they offered,
  - But if the displays were of equal size, the butterflies preferred the flowers that offered the most nectar,
  - Newly emerged butterflies visited both yellow and red flowers in their initial feedings, but the butterflies quickly discriminated between flower color, choosing to feed at the yellow, nectar-rich flowers more often than the red flowers (Weiss 1991, https://doi.org/10.1038/354227a0).

Scientific Classification

Kingdom	Animalia (animals)
Phylum	Arthropoda (arthropods)
Class	Insecta (insects)
Order	Lepidoptera (butterflies and moths)
Family	Nymphalidae (brush-footed butterflies)
Genus	Junonia
Species	J. coenia
Scientific Name	Junonia coenia

Common Buckeye Butterfly Photo Gallery

Common Buckeye Butterfly. Junonia coenia. Diagram labelled with identifying marks. Brown butterfly. Insect. Photograph and design created by the author. Copyright © 2025 Now I Wonder. All rights reserved.
Common Buckeye Butterfly. Junonia coenia. Diagram labelled with identifying marks. Brown butterfly. Insect. Photograph and design created by the author. Copyright © 2025 Now I Wonder. All rights reserved.
Common Buckeye Butterfly. Junonia coenia. Diagram labelled with identifying marks. Brown butterfly. Insect. Photograph and design created by the author. Copyright © 2025 Now I Wonder. All rights reserved.

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Christine

Christine is the creator and author of NowIWonder.com, a website dedicated to the animals and plants that share our world, and the science that helps us understand them. Inspired by lifelong exploration and learning, Christine loves to share her knowledge with others who want to connect with wild faces and wild spaces.

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