D e s e r t E x p o s u r e
Aug 2011
Southwest Wildlife
Flying in Style
Southwest New Mexico is home to a half-dozen species of swallowtails, the show-offs of the butterflies.
by Jay W. Sharp
At first glance, I thought that maybe Nicola Formichetti, who designs clothes for Lady Gaga and other celebrities, might have designed the wings of the swallowtail butterflies. On closer inspection, however, I realized my error. The designer for the swallowtails has far better taste.
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Pipevine swallowtail. (BLM photo) |
The swallowtail (family Papilionidae) — the largest and most stylish of our butterflies, with a wingspan of several inches — brings fairylike flickers of color to the croplands, drainages, bosques, playa lakes, scrublands, canyons, piñon and juniper woodlands, and mountain forests and meadows of southwestern New Mexico. Distinguished by the distinctive "tails" on its hindwings, the swallowtail takes its name from the forked tails of swallows, and it shares its name with the formal swallowtail coats of aristocratic dandies.
Like other members of its order — the Lepidoptera, which includes both the butterflies and moths (see "Butterflies Are Free," July) — the swallowtail has a head with two compound eyes, two antennae, various sensors and a coiled proboscis (an elongated mouthpart used for sipping nectar); a mid-section, or thorax, with the legs and wings; and an abdomen with genitalia and egg-laying organs. A swallowtail larva, or caterpillar, may, some say, resemble a bird's dropping — an irony, given the elegant creature it will become. It is the insect equivalent, I suppose, of Hans Christian Andersen's ugly duckling.
The swallowtail's four wings — two forewings and two hindwings — invest the insect with its elegance. They are composed of two membranous layers that are nourished and structurally supported by tube-like veins. They are covered with thousands of scales, or minute pieces of chitin, that overlap like shingles — in effect, the canvas for the butterfly's subtly or brilliantly colored patterns. The forewing and hindwing — held coupled, like a single wing, in flight — are moved by strong muscles within the thorax. On chilly days, the wings serve as solar blankets, soaking up the rays of the sun, bringing warmth to the swallowtail, which, like all insects, is cold-blooded.
The swallowtail's wings also play a crucial role in mating. Males' forewings bear "scent scales" that emit pheromones, or chemicals, that attract females. (I'm sure that most human males wish they had comparable scales.) Both swallowtail sexes' visible and defining wing colors and patterns and their invisible (to the human eye) and defining ultraviolet wing patterns help lure mates within the species.
Life Cycle
With a breeding season that typically extends from spring into fall, the male swallowtail perches and patrols across its range, prospecting for receptive females. After mating, the female lays her eggs singly or in clusters on "host" plants — those plants that will serve as the primary food for her progeny.
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Swallowtail Secrets:
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A few days later, the larvae, or caterpillars, begin to hatch. A caterpillar feasts on its host plant voraciously and grows rapidly, molting, or shedding its skin, five times to make room for its increasing size. It comes equipped to protect itself from predators. According to Richard Bailowitz and Douglas Danforth in 70 Common Butterflies of the Southwest, the swallowtail caterpillar has "a foul-smelling, forked gland behind the head called an osmeterium. It is usually hidden but can be everted [turned outwards] to deter predators." It looks much like the forked tongue of a snake.
After the caterpillar reaches one to two inches in length, it secrets itself to "pupate," or envelop itself in a protective mantle called a chrysalis. There it begins the almost miraculous transformation from a "bird dropping" to an elegant winged creature.
The swallowtail will make its way out of its chrysalis in the same season or, if it is late, in the following spring. Crinkled and wet after its emergence, it hangs upside-down near the chrysalis as blood flows into the veins of its wings, straightening them in much the way ribs extend an umbrella. Once dry, the swallowtail takes flight, now dining at nectar-filled blooms and searching for a possible mate.
Swallowtail Species
According to Steven J. Cary and Richard Holland's "New Mexico Butterflies: Checklist, Distribution and Conservation," six of the some 33 North American (and some dozen New Mexico) swallowtail species occur in southwestern New Mexico: four as residents, one as a seasonal visitor and another as an occasional stray. The six, identified most readily by their wing colors and patterns, include the pipevine swallowtail, the black swallowtail, the western tiger swallowtail, the two-tailed tiger swallowtail, the seasonal giant swallowtail and the occasional gold rim swallowtail:
- Pipevine swallowtail (Battus philenor): The pipevine swallowtail has predominantly black forewings and iridescent blue hindwings, and it has a loop of seven orange spots on the underside of its wings — a visual warning of foul taste and poison to would-be predators. It ranges from western Texas across southern New Mexico and into Arizona. It occupies open areas, from higher desert landscapes to piñon and juniper woodlands to mountain forests. It favors hilltops, where it often finds a mate. It frequently visits city gardens, where it sips the nectar from plants such as lantana and lupines. The female often lays a cluster of up to 20 eggs on the pipevine plant, which, as a host plant, will vest the caterpillar with its foul taste and toxicity. The caterpillar, generally black or smoky red, may be identified by its fleshy filaments and orange-red warts. The pipevine swallowtail may be seen from spring well into fall. With a wingspan of about 2 1/2 to 3 1/4 inches, it is the smallest of our swallowtails.
- Black swallowtail (Papilio polyxenes): In our greater region — from western Texas across southern New Mexico and into Arizona — the black swallowtail has primarily black forewings and hindwings, with two rows of yellow spots along the trailing edges of both the fore- and hindwings. Superficially, it resembles the pipevine swallowtail, a similarity that may turn back predators wary of foul taste and poison. The black swallowtail seems to prefer more open and higher areas, appearing often, from spring into fall, in gardens and cultivated fields. The male patrols hilltops, looking for a mate. The female lays her eggs singly, often on certain plants in vegetable gardens, where the caterpillar — generally green with black and yellow rings around its body — can become a nuisance.
- Western tiger swallowtail (Papilio rutulus): The western tiger swallowtail, says e-Nature.com, has "above and below, lemon-yellow with black tiger-stripes across wings and black yellow-spotted margins. One or two orange spots and several blue spots near black tail on hindwing; blue continuous all around outer margin of hindwing below. Yellow spots along outer black margin of forewing below run together into a band; uppermost spot on border of hindwing above and below is yellow." This may be "the most conspicuous butterfly in the West." It frequents the higher elevations, seeking out mountain meadows, parks, gardens, trails and roadways, especially near springs or streams. The female lays eggs singly, usually on the back side of a leaf of a host plant such as a cottonwood, willow or aspen tree. The green caterpillar, which may reach two inches in length, has on its head two yellow false eyespots with black and blue pupils. Presumably, the eyespots suggest a larger and more foreboding animal, helping deter predators.
- Two-tailed swallowtail (Papilio multicaudata): The two-tailed swallowtail has two distinguishing tails on each of its hindwings, with the outer tail measuring several times the length of the inner tail. This swallowtail has yellow wings with a thin black border on the leading edges of the forewings and a thick black border on the trailing edges of the fore- and hindwings. On each side, it has four diagonal and essentially parallel stripes, with the innermost stripe several times longer than the outermost stripe. Within the black border on each hindwing, it has a row of blue patches above a row of smaller yellow patches. The two-tailed swallowtail favors streamside canyonlands along the lower slopes of the mountain ranges, where both sexes coax nectar especially from thistle blooms, and the male takes sodium from streambank mud. The female lays her eggs on the leaves of any of several trees that serve as host plants. The caterpillar, light green, bears two yellow eyespots near its head, black and yellow bands around its neck, and rows of small blue dots along its body. The two-tail swallowtail, with a wingspan of as much as 4 1/2 inches, is the largest of
the family within our region.
- Giant swallowtail (Papilio cresphontes): The giant swallowtail, which turns up only seasonally in Grant, Hidalgo and Luna counties, according to Cary and Holland, often visits gardens in even the lowest, hottest part of our desert. Its dorsal, or top, wing surfaces are black with a striking row of yellow patches from wing tip to wing tip and a diagonal row of yellow patches across each hindwing. It tails are marked by yellow patches. The insect's ventral, or bottom, wing surfaces are yellowish tan with rows of black-outlined patches. It is especially fond of the lantana blooms in a garden. Although slightly smaller than the two-tail swallowtail in our area, its wings, in some parts of its greater range, may span more than seven inches, according to University of Florida entomologists.
- Gold rim swallowtail (Battus polydamas): The gold rim swallowtail, which wanders up from Mexico into Luna County as what entomologists call a "stray," makes its occasional appearances in open fields and in gardens. It seems to favor lantana and honeysuckle. The insect's wings are black both on the dorsal and ventral surfaces. It has a row of golden-colored patches near the trailing edges of its wings. Although entomologists include it among the swallowtails, it has no tail.
The books 70 Common Butterflies of the Southwest by Richard Bailowitz and Douglas Danforth and Butterflies of the Southwest by Jim P. Brock have useful photographs of several of the swallowtails as well as other Southwest butterflies.
Life's Hazards
All the species of swallowtails of southwestern New Mexico are "demonstrably secure globally," according to Butterflies and Moths of North America. As Cary and Holland point out, however, some species of butterflies — especially those with small and isolated populations — in New Mexico may be threatened by factors such as land use, stream alterations, habitat fragmentation, climate change and wildfires. Vigilance will be required to assure the long-term viability of our swallowtails and other butterfly species.
Butterfly Gardens
The swallowtails make elegant and colorful guests — thankfully more quiet and stylish than Lady Gaga — in your butterfly garden. Most frequently, they choose gardens with the preferred host plants for the caterpillars and favorite nectar sources for the adults. You will find a list of New Mexico's swallowtails, by county, at TheButterflySite.com (www.thebutterflysite.com/newmexico-butterflies.shtml). You will discover useful advice on establishing a butterfly garden at The Big Blend! (southwestblend.com/Butterflies/butterfly-garden-creation.htm), which lists host and nectar plants for various species.
Jay W. Sharp is a Las Cruces author who is a regular contributor to DesertUSA, an Internet magazine, and who is the author of Texas Unexplained. To read all his guides to wildlife of the Southwest, see www.desertexposure.com/wildlife.