Where Are All Those Butterflies Going?

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Monarch butterfly

Most people are familiar with the famous migratory flight of the monarch butterfly (Danaus plexippus).  These resilient colorful lepidopterans are a familiar sight twice a year in the state of Texas as they make the arduous journey to their summer fields of Canada and then back to Mexico in the fall.  With their bright “Halloween” colors of orange and black, coupled by their large size, they are one of our more conspicuous species of migratory butterfly.  But Texas holds several additional species less well known that also make annual or biannual trips to warmer haunts with the advent of autumn.  With the gradual cooling of days, a host of different species can be seen flitting over open areas on sunny mornings, some in a leisurely fashion and others at a determined rapid pace that seems to reflect the ever-impatient rabbit borne of the Lewis Carroll novel, Through The Looking Glass.

One of these is the Queen butterfly (Danaus gilippus), a close relative and mimic of the monarch.  Although slightly smaller and of darker coloration, the pattern is quite similar, enough so that very few Queen butterflies fall victims to avian predation.  Birds seem to know well and resist the distasteful toxins of the monarch, which are absorbed into their bodies during their larval stages through the toxic milkweed they consume, and the color and pattern similarities between these two species offer the queen butterfly a VIP pass as it slowly wings its way across fields and abandoned lots, flying low to the ground and seeming to stop to visit every flower.

These butterflies are principally subtropical in nature, and seldom fly far enough north into the United States to constitute a large migration pattern, but they are a common sight in the American southwest April through October.  The rest of the time is spent south of the border, and in the early fall months this is one of the most common species seen in the lower Rio Grande Valley as large numbers make their way to greener winter pastures.

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Gulf fritillary

Another very common and dazzlingly beautiful species that migrates in the state is the Gulf fritillary (Agraulis vanillae) This fast-paced flier is mad about passion vine, its host food plant, and thus is a common visitor to flower gardens where this plant is found.  Bright orange on top and brown and silver beneath, they are easily distinguishable from other species.  Gulf fritillaries are not true fritillary butterflies, but rather members of the genus of subtropical butterflies known as heliconians.

One of our most prolific mass-migrators is the American snout butterfly (Libytheana carinenta).  Inconspicuous when at rest on a twig, after being closely approached they burst forth suddenly in an explosion of orange.  On any given year in the fall snout butterflies can be seen winging their way south, usually in dozens but occasionally by the thousands.

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Top L: Snout butterfly; Top R: Red admiral; Bottom L: Painted lady; Bottom R: Cloudless sulphur

Two other familiar species of butterflies belong to the family known as ‘brush foots’.  The red admiral (Vanessa atalanta) is a handsome species, chocolate brown with bright bars of scarlet on the fore and hind wings and white dots or patches on the wingtips.  This species normally overwinters beneath rock overhangs or in dense brush, and during years of high population density large numbers of adults that have overwintered in warmer climates break northward for higher and cooler elevations.

The painted lady (Vanessa cardui) is a cosmopolitan species that takes this same migration pattern to a global scale.  Fast and erratic fliers, these noticeable insects with blue and brown eyespots on the underside of the hindwings and the telltale pink slash of color beneath the forewings are one our most common species, and migratory groups traveling north from their winter haunts below the equator can number in the millions.

A vibrant and easily identified migrator is the cloudless sulphur (Phoebis sennae).  With its bright highlighter-yellow coloration and zippy, darting flight pattern its presence in a park or backyard is hard to miss.  In late summer large numbers of these butterflies fly northward high in the air.  Their determination is in direct contrast to their springtime behavior, where they can often be approached quite closely as they visit bright flowers or mud puddles.

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Painted lady

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Painted lady, showing undersides of wings

One of our smallest migratory species is the fiery skipper (Hylephila phyleus).  Skippers are a strange paradox in the lepidopteran world, and appear to be a weird mixture of both moth and butterfly.  They are diurnal, but possess the general stout body structure common to moths.  Of the confusing array of similarly marked species of skipper that flit about gardens, roadsides, and open fields wherever flowers abound in our state, the fiery is an example of a specific migrator.  This species, like many types of lepidoptera, is sexually dimorphic, meaning the sexes can be distinguished visibly by physical coloration, pattern, or other characteristics.  Males are clothed in the brilliant yellow-orange that gives the species its common name, and females are, as is often the case in nature, more somberly hued.  Each September large numbers of fiery skippers can be seen in north Texas as they dance among the goldenrod and dandelions at road’s edge.

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Fiery skippers, male (top) and female (below)

Butterflies, like birds, are well known for their migratory habits, but few think of moths migrating.  However, one of the most epic and amazing migration stories comes from the natural history of the black witch moth (Ascalapha odorata).  Chiefly a subtropical species, the black witch is a truly impressive insect.  Called Mariposa de la muerte or “butterfly of death” in its native Mexico, these bat-like giants with wingspans of up to seven inches fly north across the border in the month of June, their departure coinciding with the southwest’s monsoon season.  During this time, and on through the fall as late as October they can be common visitors to lights across the state.  Their adult stage, which only lasts a month or less, leaves them no opportunity for actual overwintering sites, but the species appears to make a general course across the heartland from Texas to North Dakota, with wandering strays appearing in such unlikely northern places as New York and even Manitoba, Canada.  Unlike butterflies, and in true noctuid fashion, the black witch migrates at night.  One interesting and unsolved mystery of their travels involves huge “fallouts” of black witches dropping to the ground in the middle of tropical storms, where their bodies sometimes litter the sidewalks of coastal port towns along the Gulf of Mexico.  Apparently the moths travel in the eye of hurricanes, a phenomenon whose exact reasons are still unknown.

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Black witch moth

The arrival of fall brings a change of pace to our lives in Texas, bringing cooler temperatures, shorter days, and the beautiful adornment of native hardwoods with cloaks of multi-colored foliage.  It also brings about an influx of butterfly activity, so the next time you step outside and notice an unusual number of butterflies on the wing, stop to wish them well.  They just may have a long way to go.

References:

Brock, J.P. & K. Kaufman. 2003. Kaufman Field Guide to Butterflies of North America. Houghton-Mifflin

The Black Witch Moth: Its Natural & Cultural History – www.texasento.net/witch.htm

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