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Unlikely Pair

At a trailhead in the Catskills, I once watched two very different-looking butterflies in close association with one another.  Perched on tree branches, basking on the dirt ground, even appearing to engage in courtship, this pair made an improbable couple.  Within moments, there were several butterflies of each type filling the parking area.  Some of them had black wings with a vertical white band, while the others had lustrous, blue-black wings without bands.  What they had in common was a similar wing shape, bordered by blue and white chevrons and with two pale spots near the tip.

Recognizing them as the White Admiral and the Red-spotted Purple, I was surprised by the reason for their fraternizing: they are subspecies of the same butterfly (Limenitis arthemis ssp. arthemis and astyanax, respectively).

How could such dissimilar insects have been classified as one species?  In the Northeast, where their ranges overlap, they often mate with each other, producing healthy, fertile hybrids with variable markings.  Hybrids’ ability to reproduce is key; occasional matings between other species, such as the Red Admiral and West Coast Lady, result in infertile hybrids.

Each subspecies has evolved with a unique survival strategy.  The White Admiral, confined to northern states and Canada, relies on disruptive coloration to confuse predators.  Its contrasting bands of black and white make the insect’s overall shape and size unclear.

The Red-Spotted Purple, whose range extends to the southern states, mimics the Pipevine Swallowtail, a large blue/black butterfly inhabiting the same area.  Pipevine Swallowtail larvae eat pipevine (Aristolochia spp.), a plant containing noxious chemicals.  These chemicals are stored in the body, making both larva and adult distasteful to predators, who quickly learn to avoid similar-looking butterflies.  The Red-spotted Purple’s protective strategy of resembling a distasteful species is called Batesian mimicry (see below).

Mimicry among the Admirals

Red-spotted Purples aren’t the only admirals to benefit from looking like something else, nor is duplicity in this subfamily limited to wing color.  Early-stage larvae and chrysalides of many admirals are camouflaged to resemble brown-and-white bird droppings.

The Viceroy, common in most of North America, has long been considered a Batesian mimic because it resembles the distasteful Monarch; however, it’s been discovered to be unpalatable, too.  The Viceroy is smaller than the Monarch but has strikingly similar coloration and markings.  It can be identified by the extra black line across the hindwing.

Because of its wide distribution, the Viceroy over-laps the southern range of another milkweed butterfly, the Queen.  In these regions, Viceroys tend to mimic the darker-orange coloration of Queens. While the difference in markings may be obvious to us, a bird in attack mode is likely to be put off by a warning flash of orange.

A West Coast species, the Lorquin’s Admiral, has vertical white bands and orange tips on black wings, giving it the alternate name of Orange-tip Admiral.  It resembles the Sister, a Southwest-area admiral.  The Sister has a crisp orange patch on the forewing and a curving band of white against black wings.  Sisters can often be seen at wineries, imbibing on spilt grape juice.  Their larvae feed on leaves of canyon live oak and coast live oak, a diet that may render both larva and adult unpalatable to predators.  In California, where both species’ ranges overlap, this would confer benefit to the Lorquin’s Admiral.

Fearless in Seattle

I’m fond of the Lorquin’s Admiral (named after nineteenth-century collector Pierre Lorquin) because it has been a dependable visitor to my city yard.  Egg-laying females have made forays into the branches of my apple and cherry trees.  In early summer I watched a Lorquin’s Admiral work over a disreputable-looking patch of fava beans.  Aphid honeydew was its objective, and it found enough to stay the morning.  (I hadn’t removed the plants because I’d noticed many ladybug larvae on them; the butterfly was an unexpected bonus!)

Admirals fly with a characteristic flap-and-glide motion.  The Lorquin’s flight style was described by John Adams Comstock, author of the classic 1920s book, Butterflies of California, as “a series of short twitching motions with the wings held nearly flat, interspersed with leisurely volplaning.”

The butterfly basks with its wings held at a 45-degree angle, alternately opening and closing them.  It’s strongly territorial, darting out to investigate intruders.  At a nearby park, I’ve spent an afternoon watching a Lorquin’s Admiral perch in a chestnut tree and repeatedly chase dragonflies.  The butterfly has reportedly been seen lunging at and harassing seagulls.  You have to admire such spirit!

The Admirable

The name admiral is a North American corruption of admirable, a gentler term used in England.  The Red Admiral (Vanessa atalanta) isn’t a true admiral, although they’re all part of the same family Nymphalidae (also called brush-footed butterflies for their shortened, brush-like forelegs).  Admirals belong to the subfamily Limenitidinae, while Red Admirals are in the subfamily Nymphalinae, along with anglewings, tortoiseshells, Buckeye, Painted Lady and others.

Naming is an ongoing process among lepidopterists.  Jeff Glassberg, president of the North American Butterfly Association, says that NABA is beginning to use the term Red-spotted Admiral for the species Limenitis arthemis.  This name would apply to Red-spotted Purples, White Admirals and their hybrids.

In Your Garden

Plant milkweed, lilac, buddleia, and composite flowers (aster, zinnia, bidens) to attract nectar-seeking admirals.  They're also fond of thistles in the wild.  They sip minerals and/or amino acids from rotting fruit, tree sap, decaying wood, wet dirt, animal scat or carrion.

Admirals spend the winter months as a tiny larva inside a rolled-up leaf.  After nibbling the leaf edges, the larva secures the stem to the tree with silk and then encloses itself inside its “sleeping bag,” or hibernaculum.  In winter, look on host trees, such as wild cherry and poplar, for a curled leaf that hasn’t fallen off.  You can clip off the twig and fasten it with a clothespin to a similar tree in your yard.  In spring, when new leaves form, the larva will crawl out of its hibernaculum and begin to eat the tender growth.  If you use dormant spray on your apple or cherry tree, remove the twig temporarily; the spray will smother the caterpillar.  Then, enjoy watching the development of your admirable admiral!

The Butterflies

Lorquin’s Admiral (Limenitis lorquini).  Range: Western states, B.C.  Host plants: willow, aspen, cottonwood, cherry, apple.

Red-spotted Purple (Limenitis arthemis ssp. astyanax). Range: Eastern U.S. Host plants: willow, aspen, poplar, wild cherry, hawthorn, apple. 2-3 broods.

Sister (Adelpha bredowii).  Range: Southwest.  Host plants: canyon live oak, coast live oak. 2 broods.

Viceroy (Limenitis archippus).  Range: Most of U.S., except West Coast.  Host plants: willow, poplar, aspen, cottonwood, apple, cherry. 2-3 broods.

Western Admiral (Limenitis weidemeyerii).  Range: Rockies, Southwest.  Host plants: willow, aspen, cottonwood. 1-2 broods.  Note: The Western Admiral resembles the White Admiral, although their ranges do not overlap.

White Admiral (Limenitis arthemis ssp. arthemis). Range: Northeast U.S., Great Lakes, Canada. Host plants: birch, willow, poplar, aspen. 1-2 broods.

Types of Mimicry

Batesian.  Palatable species evolve to resemble poisonous/unpalatable species.  Theory is named after Henry Walter Bates, nineteenth-century naturalist who made detailed observations of butterflies in the Amazon Basin.

Muellerian.  Poisonous/unpalatable species evolve to resemble each other, using color model of most common species.  This results in less overall predation since predators need to learn only one color model.  Theory is named after Fritz Mueller, Amazon naturalist and contemporary of Bates.
 

Article by Claire Hagen Dole, Publisher/editor of Butterfly Gardeners' Quarterly. #18, fall
1998.  Issue also includes article on rock gardening for butterflies. $2.50 ppd. from BGQ, PO Box 30931, Seattle, WA 98103.

Return to Butterfly Gardeners' Quarterly Index
 

© copyright 1998 by Claire Hagen Dole; all rights reserved.