The Tired Monarch

April 9, 2008

This morning, I noticed a monarch butterfly fluttering around the butterfly garden outside the Butterfly Center. 

It was a female (see photo at the bottom of this post), and her wings were faded and tattered; she looked tired and worn-out.  This was no locally-grown monarch, but was almost certainly one of the migrants returning from the highlands of Central Mexico.

Monarchs clustered on tree trunk at their
overwintering grounds

Monarch migration – how and why it happens – is fascinating, and we’ll discuss that in a post coming next week. In the meantime, you can check out Journey North, an excellent “citizen science” program designed for K-12 students that focuses on the global study of wildlife migration(the general public is also welcome to participate). Monarch butterflies are one of their flagship organisms. 

Monarch Watch, a non-profit organization based at the University of Kansas, coordinates efforts to tag migrating monarchs. Yes, you can actually put tiny, numbered tags on these butterflies! Recovering tagged butterflies has allowed researchers to map the Monarchs’ migration route over the past decade or so and has helped us to understand the biology and physiology behind this unique phenomenon.

Here in Houston things get confusing, because not all of our monarchs leave for the winter.  Local butterfly enthusiasts have noticed both adult butterflies and caterpillars throughout the winter for the past several years.  Perhaps it is because our winters have been milder of late, or perhaps it’s due to the Mexican milkweed (Asclepias curassavica, aka “butterfly weed”) that many butterfly gardeners are planting.


Last instar monarch caterpillar feeding
on Asclepias curassavica

In contrast to our native milkweeds, this tropical species doesn’t die back in the winter – which means that monarchs have a place to lay their eggs and grow new caterpillars all year round. 

If you see a fresh-looking individual at this time of year, it is definitely one that didn’t bother to make the long trip south.  But in late March and April, keep your eyes open for those tired and faded butterflies – and think of the immense and amazing trip they have made to get here!

If your interest has been piqued, the Houston Chronicle has published several articles about Monarchs this springs: on their habitat, the science behind their migration and travel options to see millions of Monarchs at their overwintering sites in Mexico.

Do you know how to tell monarch males and females apart?  It’s subtle, but easy once you know what to look for.  Males have thin black pigmentation around the veins on their upper wing surface, and have a pair of black spots or swellings in approximately the middle of the hind wing (they are vestigial scent glands).  Females don’t have these black thickened places, but have thicker black pigmentation around their veins, giving them a darker look overall.


Female Monarch butterfly (no spots)


A Male Monarch Butterfly. See the spots?

Authored By Nancy Greig

Dr. Nancy Greig is the founding director of the Cockrell Butterfly Center, which she oversaw from 1994 to 2016. As emeritus director she continues to work with the museum doing outreach and education. Her academic training is in botany and entomology, with a specialty in the interaction between insects, especially butterflies, and plants. In addition to cultivating backyard butterflies, she grows vegetables and bees

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