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Monarch Butterfly (Danaus plexippus)

Detailing the physical features, habits, territorial reach and other identifying qualities of the Monarch Butterfly.

 Updated: 9/18/2019; Authored By Staff Writer; Content ©

The king of the North American Butterflies is the Monarch and its reigns may be ending as its food availability dwindles along its migration route.

Monarch Butterfly Videos

Monarchs taking lantana nectar

Monarch Butterflies are a becoming a less common sight throughout North America. According to the Center for Biodiversity in Tucson, Arizona, their numbers have dropped almost 80% over the past 20 years. While cold temperatures in the summer made them rare in the extreme northern regions, a variety of factors is responsible for their diminishing numbers in the southern provinces and states. Natural disasters, like the wildfires that have ravaged California, destroy vegetation that the Monarch needs for rest and nourishment. As of 2019, these western populations are on the verge of collapse. Rapid development of their habitat across the rest of the U.S. and Canada removes food plants, making it harder to find places that will support the next brood, let alone the next generation. The use of pesticides on agricultural fields also kills the butterfly as it crosses continents. Climate change leading to hotter winters in Mexico, where the species overwinters, is drying out and killing the trees the butterfly depends on. The declining numbers of the Monarch led to an assessment for their protection under the Endangered Species Act in the United States. A decision on whether or not to list the Monarch as endangered was expected in June of 2019, but was then extended to December 2020.

Monarch Butterflies are migratory. They live in the northern region of the continent during the summer and then fly south to warmer regions to live during the winter months. A single Monarch can cover thousands of miles of flight in one season. Millions of this large butterfly fly together to the southern U.S. states and Mexico to avoid the bitter cold winters of Canada and the northern U.S.. In the spring and summer, legions of them travel back north in waves, or pulses. Their arrival in many towns is celebrated, and now citizens help scientists by documenting and sharing data like local population counts (or good estimates), dates of arrival and departure, and geographic location. This invaluable information has helped bring to light the dire situation that Monarchs are now facing. It may also help in reviving the butterfly's dwindling numbers.

The mascot of many organizations, the orange and black Monarch is likely very familiar, even if never before seen in real life. Photos and drawings of it are easy to find online. A black border around the wings has rows of tiny white dots. The hairy black body sports a few tiny white dots on its head and 'neck', and small white dashes on both sides of the black abdomen. Colors begin to pale as the butterfly becomes weathered. The related Viceroy Butterfly looks similar to the Monarch Butterfly, but has slight differences in both pattern and color. A discerning eye should be able to tell the two apart.

Monarchs tend to gravitate towards open meadows or along the road, traversing the terrain in the search for the much favored milkweed plant. They are active from May to early fall in most areas, but year-round in Mexico, Florida, Hawaii, and Texas. Like all butterflies, the Monarch begins as a caterpillar, feeding on foliage and flower buds where available. It is black with white and yellow rings from head to tail. Growing its favorite plant to eat - any variety of milkweed - is a great way to help support this species locally. Grow plants in the Asclepias genus (Milkweed's scientific genus); ask for them by name at your local plant nursery, or order seeds online. To learn more about what you can do to help Monarch butterflies in your country, visit these resources:

in the U.S.: United States' Save the Monarch campaign
in Canada: Canada's Save the Monarch campaign
en México: WWF-México: Mariposas Monarca y Protejamos a las monarca
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Taxonomic Hierarchy
Kingdom: Animalia
  Phylum: Arthropoda
    Class: Insecta
      Order: Lepidoptera
        Family: Danaidae
          Genus: Danaus
            Species: plexippus
Identifying Information
Scientific Name: Danaus plexippus
Other Name(s): King Billy Butterfly
Category: Butterfly or Moth
Size (Adult; Length): 89mm to 105mm (3.47in to 4.10in)
Colorwheel Graphic Colors: orange; black; white
Descriptors: flying
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Territorial Reach (A-to-Z)
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Note: An insect's reach is not limited by lines drawn on a map and therefore species may appear in areas, regions and/or states beyond those listed above as they are driven by environmental factors (such as climate change), available food supplies and mating patterns. Grayed-out selections indicate that the subject in question has not been reported in that particular territory. U.S. states and Canadian provinces / territories are clickable to their respective bug listings.

Butterfly and Moth Anatomy
Graphic showing basic anatomy of a common North American butterfly and moth insect
Antennae: Butterflies and Moths have a pair of antennae on the head used as sensors.
Head: The head is home to the insect's eyes, antennae, and proboscis.
Thorax: Home to the three pairs of legs as well as vital internal organs.
Abdomen: Contains vital internal organs such as the heart(s) and reproduction facilities.
Forewing: The upper, forward wing pair used for flying.
Hindwing: The lower, rearward wing pair used for flying.
NOTE: Butterflies and Moths are part of the Lepidopteran order as they share many similarities.