Wild Facts About The Monarch Butterfly

How To Identify Monarch Butterflies

Adult Butterflies

Monarch Butterflies are large butterflies with wingspans up to 5 inches (12.7 cm) and dark eyes.
Their bodies are black with white polka dots.
Above:
- Bright cinnamon orange with wide black wing veins.
- Black wing borders with 2 rows of tiny white spots.
Below:
- Same as above but paler overall.
Monarch Butterflies are famous for their multi-thousand kilometer migration and love of milkweed plants.
Monarch Butterflies live throughout the eastern United States during the summer months.
- Look for them in sunny locations such as along roadsides, in old fields, utility cuts, and home gardens.

Caterpillars

Thin, black, yellow, and white stripes,
Head is also banded in black and yellow
A8 and T2 bear long, thin filaments
Look for them on young-growth Milkweed plants (Asclepias), especially Swamp Milkweed (Asclepias incarnata).

A black, yellow, and white striped Monarch Butterfly caterpillar feeding on a milkweed leaf. Danaus plexippus. — Monarch Butterfly caterpillar Danaus plexippus Insect Photograph taken and design created by the author Copyright © 2025 Now I Wonder All rights reserved

First, An Excellent Defense

Monarch Butterfly caterpillars feed exclusively on plants in the Milkweed genus Asclepias.
These plants produce toxic compounds called cardiac glycosides that deter many herbivores.
However, instead of being deterred by the presence of these toxic compounds in milkweed leaves, Monarch caterpillars take advantage of them for their own defense against predators.
- The caterpillars incorporate the glycosides into their own body tissues and retain the toxins throughout their metamorphosis into adult butterflies.
  - Monarchs in all life stages are unpalatable to many predators, especially insectivorous birds.
  - The bright colors and bold patterns seen in both caterpillars and adult butterflies warn potential predators that the insects are toxic (called aposematic coloration).

With seventy-seven species of milkweeds found in the United States, female Monarch Butterflies have options about where to lay their eggs to maximize their offspring’s chances of survival.
- Female Monarch Butterflies seem to prefer laying their eggs on Swamp Milkweed (Asclepias incarnata); this species seems to be especially nutritious for the caterpillars, if not especially high in cardiac glycosides.
- But female butterflies are infected with a protozoan parasite called Ophryocystis elektroscirrha choose to lay their eggs on other milkweed species that have higher concentrations of glycosides instead, and thus reduce parasitic growth in the offspring (Lefèvre et al. 2011, https://doi.org/10.1111/j.1365-2656.2011.01901.x

Two orange, black, and white butterflies sipping flower nectar. Monarch Butterfly. Danaus plexippus. — Monarch Butterfly Danaus plexippus Insect Photograph taken and design created by the author Copyright © 2025 Now I Wonder All rights reserved

Second, An Even Better Offense

Unfortunately for Monarch Butterflies, no defense provides one hundred percent protection against predators.

Battle Of The Favorites

Perhaps one of the most surprising predators of Monarch Butterfly eggs and caterpillars is one of the most beloved and familiar insect to many Americans—ladybugs.
Also called ladybird beetles and lady beetles, ladybugs are predaceous beetles that usually feed on aphids, which are common garden and agricultural pests.
- Many species of ladybugs exist in the eastern United States; the larvae of one invasive species called the Asian or Harlequin Lady Beetle (Harmonia axyridis) attacked and killed Monarch larvae even in the presence of aphids (Koch, Ventette, and Hutchison 2005, https://doi.org/10.1603/0046-225x-34.2.410).
  - The larvae and adults of at least the Asian or Harlequin Lady Beetle attacks and eats Monarch caterpillars.

And The Hits Keep On Coming

While many birds avoid eating Monarch caterpillars and adult butterflies, other predators have learned to bypass or overcome the Monarch’s toxicity.

Predators of Monarch eggs include:
- Other types of beetles including:
  - Ground Beetles (family Carabidae),
  - Soldier Beetles (family Cantharidae),
- Orthopterans including:
  - Short-Horned Grasshoppers (family Acrididae), such as the Differential Grasshopper (Melanoplus differentialis),
  - Tree Crickets in genus Oecanthus,
  - Ground Crickets in genus Allonemobius,
  - Katydids in genus Neoconocephalus like Round-tipped Conehead Katydid (Neoconocephalus retusus)
- Hemipterans (true bugs) including:
  - Common Damselbugs (Nabis americoferus),
  - Spined Soldier Bugs (Podisus maculiventris),
  - Jumping Tree Bugs (Plagiognathus spp.)
- Earwigs (family Forficulidae) including Common Earwigs (Forficula auricularia)
- Lacewing larvae (family Chrysopidae),
- Ants including:
  - Acrobat or Cocktail Ants (Crematogaster),
  - Tapinoma sessile,
- Arachnids (class Arachnida) including:
  - Jumping Spiders (family Salticidae),
  - Daddy Long Legs (order Opiliones) (Hermann et al 2019, https://doi.org/10.1038/s41598-019-50737-5).

Several of these Monarch egg predators also attach Monarch caterpillars, including:
- Ground Beetles (family Carabidae),
- Soldier Beetles (family Cantharidae),
- Tree Crickets in genus Oecanthus,
- Ground Crickets in genus Allonemobius,
- Spined Soldier Bugs (Podisus maculiventris),
- Lacewing larvae (family Chrysopidae),
- Common Earwigs (Forficula auricularia),
- Various ant species,
- Jumping Spiders (family Salticidae),
- Daddy Long Legs (order Opiliones) (Hermann et al 2019, https://doi.org/10.1038/s41598-019-50737-5).

An orange, black, and white butterfly sipping nectar from an orange flower. Monarch Butterfly. Danaus plexippus. — Monarch Butterfly Danaus plexippus Insect Photograph taken and design created by the author Copyright © 2025 Now I Wonder All rights reserved

More Than One Way To Keep True

Each fall, the eastern North American population of Monarch Butterflies migrate from their breeding sites in Canada and the northern portions of the United States to their overwintering sites in the mountains of central Mexico.
- In the spring, different individuals reverse course and migrate back into the eastern United States.

Monarchs orient themselves during their long-distance migrations by means of a time-compensated sun compass that uses the directional cues provided by the angle of the sun, and a magnetic compass that uses the geomagnetic field generated by Earth’s rotation.
Both systems recalibrate to either a southward or northward orientation, depending on the time of year and the direction the Monarchs must migrate to survive.
- The calibration happens in response to temperature changes:
  - As temperatures drop in the northern eastern United States in the fall, the butterflies’ internal compasses calibrate to send them south.
  - The reverse occurs in the spring, when the butterflies experience decreasing temperatures at their overwintering spots in Mexico, and their compasses calibrate to send them north (Shively-Moore, Matter, and Guerra 2025, https://doi.org/10.1371/journal.pone.0328737).

A newly emerged orange and black Monarch Butterfly drying its wings next to its chrysalis. Danaus plexippus. — Monarch Butterfly Danaus plexippus Insect Photograph taken and design created by the author Copyright © 2025 Now I Wonder All rights reserved

Scientific Classification

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

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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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