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Monarchs in the Coachella Valley
Before planning a monarch garden, it helps to understand when monarchs are here, where they come from, and how they move through the Coachella Valley so you can provide the right habitat when these remarkable butterflies pass through.
Two North American Populations
A remarkable thing about monarch butterflies (Danaus plexippus) is that although it is a single species, it largely exists as two separate populations: one east of the Rocky Mountains and one to the west. There are smaller scattered populations but most of the monarchs on Earth occur within these two populations.
Eastern monarchs migrate from as far north as Canada to the oyamel fir (“sacred fir”) forests in the mountains west of Mexico City. During this fall migration, a single butterfly can travel more than 3000 miles.
Western monarchs typically migrate towards California, where they overwinter in small forested areas along the Pacific coast from just north of San Francisco south to Baja. While a shorter trip than their Eastern counterparts, it is no less remarkable.
Western Monarch Migration
In the late summer, environmental cues trigger migratory behavior. Monarchs delay reproductive development (this is called diapause) and begin to travel away from their breeding grounds towards their overwintering sites.
These monarchs must traverse some of the most challenging landscapes of North America, including deserts, mountain ranges, some of the most intensely farmed landscapes on Earth where pesticide use is widespread, and urban landscapes virtually devoid of habitat.
After traveling these vast distances, western monarchs spend the winter clustered in groves of trees along the California coast. Historically, native Monterey pines and Monterey cypress provided much of this habitat. Today, many monarchs also overwinter in eucalyptus groves, where the trees create the cool, protected microclimate the butterflies need to survive until spring.
We are still studying and learning new information about monarch behavior. Studies have shown that some monarchs from the Southwest migrate to central Mexico, where they overwinter alongside Eastern monarchs, while others from the same area migrate to overwintering sites in California. What prompts this migration shift remains unknown.
Migration map from Monarch Grove in Pismo Beach. Shows other California overwintering sites.
Did You Know?
Like Goldilocks, monarchs are looking for conditions that are "just right." Too cold and they risk freezing. Too warm and they become active, burning the energy reserves they need to survive the winter and complete their return journey.
The Relay Race
Beginning in late winter to early spring, environmental cues trigger breeding to resume and the same monarchs start migrating back to their breeding grounds. But unlike the fall migration, which took a single butterfly, it will take multiple generations, each flying a bit further, to complete this migration over spring and summer.
Fall Migration
One butterfly makes the journey to the California coast.
🦋 → 🌲🌲🌲
Migratory Generation
⬇️
Spring Migration
Unlike fall migration, which is completed by a single butterfly, the spring migration is completed one generation at a time.
🦋
Overwintered Adult ➡️
🥚🐛🦋 Generation 2 ➡️
flies north
🥚🐛🦋 Generation 3 ➡️
continues north
🥚🐛🦋
Generation 4
repopulates breeding range
Monarchs in the Coachella Valley
Although the majority of North American monarchs migrate, we are learning that in warm weather climates like southern Florida, parts of Arizona, and here in the Coachella Valley may host monarchs year-round. These resident populations breed throughout the winter on native evergreen milkweed.
Coachella Valley: The monarchs in the Coachella Valley arrive late September to early October depending on the weather. These monarchs breed all winter and lay eggs on the local native evergreen Rush Milkweed, Asclepias subulata.
Monarch development is strongly influenced by temperature, with approximately 84°F considered ideal. Monarchs regulate their body temperature through their behavior. During cold winter mornings they roost until the sun warms them enough to fly. During periods of extreme summer heat they seek shade or other protected locations and become less active until temperatures become more favorable. In late spring, as daytime temperatures begin reaching 100°F, most monarchs move to cooler locations. This ability to wait out short periods of unfavorable weather helps explain why an occasional monarch may still be seen in the Coachella Valley during the summer, even when daytime temperatures exceed their preferred range.
Research is underway to determine where our local monarchs spend the summer. We believe many move to higher elevations, such as the High Desert and our surrounding mountains, but more study is needed. Because monarchs occasionally appear in the Coachella Valley during the summer, we continue monitoring year-round through the Monarch Larva Monitoring Project. Every observation helps us better understand how monarchs use our unique desert environment.
When Are Monarchs Here?
Unlike many parts of North America, the Coachella Valley has native evergreen Rush Milkweed. Queens are present throughout the year, while monarch activity is concentrated from October through April. Because native milkweed remains available year-round, DesertStrawHouse continues monitoring throughout the year through the Monarch Larva Monitoring Project.
J F M A M J J A S O N D
🦋 Monarchs
👑 Queens
🌿 Rush Milkweed
Typical timing. Seasonal activity may shift slightly depending on weather.
Is It a Monarch?
If you are from anywhere in the US, you are probably familiar with the monarch butterfly. It is often the only butterfly people can identify. It’s no wonder these graceful creatures stand out due to their large size and bright orange and black coloring.
But did you know not every orange and black butterfly you see is a Monarch?
The queen and monarch butterflies are some of the most commonly misidentified butterflies in the Coachella Valley. Learning the differences helps us better understand local monarch populations and improves the quality of community science observations
Queens
Queen butterflies are present in the Coachella Valley throughout the year. During the hottest summer months, many butterflies mistaken for monarchs are actually queens. Learning to tell them apart helps us better understand both species and accurately monitor local monarch populations.
Queen butterfly
How to tell the differences between Monarchs, Queens, and Painted Ladies
Monarch Caterpillar
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Look for two sets of fine filaments, one pair at the front and one at the rear.
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Monarch caterpillars are patterned in bands of yellow, white and black that generally appear similar in thickness.
Queen Caterpillar
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Look for three sets of filaments, two longer pairs toward the front and a shorter pair near the rear.
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Queen caterpillars have less even patterning; their thicker black bands contain dabs of yellow, and thin black lines overlay white sections. Faint red may be seen where the filament meets the body.
Monarch Butterfly
(Danaus plexippus):
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When the wings are closed, the fore- and hindwings only have white dots within black borders.
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Both fore- and hindwings have very bold black lines creating a “stained glass” look.
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Hindwings are lighter orange while forewings are mostly a deep amber.
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A slightly larger wingspan allows monarchs to glide more and flutter less.
Queen Butterfly
(Danaus gilippus):
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Separate species of butterfly not the female of the monarch.
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When the wings are closed, look for white dots both within the black borders and on the forewings.
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Forewings lack the bold black lines that monarchs are known for.
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Fore- and hindwings are more uniformly orange, with a brownish tint to their coloring.
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A slightly smaller wingspan gives queens a more fluttering flight than monarchs.
Painted Lady (Vanessa cardui):
Although similar in color, painted ladies have a very different wing pattern with scalloped orange wings, black patches, white markings near the wing tips, and four eyespots on the underside of the hindwings.
Why Do Monarchs and Queens Look So Similar?
Monarchs and queens are both members of the milkweed butterfly subfamily (Danainae). As caterpillars, both feed on milkweed and store protective cardenolides that make them distasteful to many predators. Their similar orange and black coloration is an example of Müllerian mimicry, in which two genuinely protected species share the same warning signal. Predators that learn to avoid one are more likely to avoid the other, benefiting both species.