D e s e r t E x p o s u r e
July 2011
Southwest Wildlife
Butterflies Are Free
...and provide plenty of free eye candy in southwestern New Mexico, where you can glimpse 40% of all US butterfly species.
by Jay Sharp
Altogether nearly 250 species of butterflies populate the southwestern quadrant of New Mexico, according to authorities Steven J. Cary and Richard Holland in their "New Mexico Butterflies: Checklist, Distribution and Conservation." This represents more than 80% of all the species found throughout New Mexico, more than 60% of all the species found across the Southwest, and more than 40% of all species found in the entire continental United States.
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Atlantis fratillary, upside-down, taking nectar from one of the daisy-like plants. Common in the higher canyons of the mountains. (All photos by Jay W. Sharp) |
The wide variety of these winged jewels of southwestern New Mexico reflects the diversity of the landscape and habitats. It is a place where the Continental Divide sends some streams flowing eastward, toward the Gulf of Mexico, and others flowing westward, toward the Pacific Ocean. It is a place where the environmental influences of the Chihuahuan Desert, the Sonoran Desert, the Rocky Mountains and the Sierra Madre converge. Our butterflies occupy almost every environmental niche — including the desert basins' playa lakes, grasslands, scrublands and drainages; the mountain ranges' oak and juniper woodlands, ponderosa pine forests and lofty meadows; and the 7,000-foot-high San Augustine Plains' grasslands.
Range, Habitat and Diet
As Richard Bailowitz and Douglas Danforth note in their book, 70 Common Butterflies of the Southwest, "Butterflies are everywhere, in cities and wilderness areas from the lowest, driest, hottest deserts to far above timberline on the cold, wind-swept slopes of the Rocky Mountains." Their numbers and activities tend to peak during mid- to late summer.
Many of our species — for instance, some of those known collectively as "skippers" — maintain a full-time residency in all or at least some of the counties of southwestern New Mexico. Others — for example, some of the "metalmarks" — make regular seasonal appearances. Still other species, from various butterfly families, stray irregularly into southwestern New Mexico from far western Texas, southeastern Arizona and Mexico's northern Chihuahua.
During the months in which it mates and lays eggs, a specific species will frequent the plants that will serve as food, or a dietary "host," for its larvae. For instance, during the warmer months of the year, the southern dogface — common and widespread across southwestern New Mexico — will be found mating and laying eggs among yellow bells, which are distinguished by blooms with trumpet-like shapes. The painted lady, also common and widely distributed, will be found mating and laying eggs near daisy-type plants, which are marked by blooms with multiple petals. When not mating, butterflies seek out the wide diversity of the flowers that provide nectar, often choosing, as the US Forest Service says, bloom clusters "that provide a landing pad and abundant rewards."
Body Basics
Butterflies — and moths — belong to the ancient and huge taxonomic order called by the scientific name of "Lepidoptera," Latin for "scale wings." The order evolved, according to North Carolina State University entomologist John R. Meyer, some 230 million years ago, and it now includes well over 100,000 highly varied species worldwide.
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One of several species of roadside skippers, which are often difficult to distinguish. |
As with all insects, an adult member of the order has three principal parts to its exoskeletal body, and it has three pairs of legs and two pairs of wings. The first body part, the head, has two compound eyes (that is, eyes with multiple lenses), various sensing organs, two antennae and a coiled proboscis. The second part, the thorax, bears the insect's legs and its wings — which are covered with the shingle-like scales that form the order's diverse patterns and colors. The third part, the abdomen, contains the insect's genitalia and egg-laying organs.
The order's larva, or caterpillar, has a sturdy head capsule with several simple eyes (that is, eyes each with a single lens) and chewing mouth parts but no antennae or proboscis. It has a soft and elongated body with a thorax that has three pairs of true legs and an abdomen that has several pairs of hook-tipped "prolegs."
Both butterflies and moths often have defense mechanisms that help protect them from predators. Some adult species have on their wings eye-like images, or "eyespots," that mimic the stare of larger animals, giving would-be predators second thoughts about attacking. Some caterpillars have eye-like images on their bodies. One caterpillar, of the puss moth (native to the Texas Gulf Coast), has venomous hairs that penetrate the skin, producing an intense burning and severe rash. The monarch and queen butterflies, rendered poisonous by a larval diet of milkweeds, make predators quite ill, discouraging attacks. The viceroy butterfly has evolved wing patterns and colors that resemble those of the monarch, suggesting to predators that the viceroy, too, may be poisonous.
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An aging hackberry emperor, its wings beginning to show the wear and tear of age. The hackberry emperor often takes refuge near hackberry thickets in mountain foothills. |
"From a taxonomic standpoint," says Meyer, "the distinction between moths and butterflies is largely artificial — some moths are more similar to butterflies than to other moths. As a rule, butterflies are diurnal [active primarily during the daylight hours], brightly colored, and have knobs or hooks at the tip of the antennae. At rest, the wings are held vertically over the body. In contrast, most (but not all) moths are nocturnal [active primarily during the nighttime hours]. They are typically drab in appearance, and have thread-like, spindle-like, or comb-like antennae. At rest, their wings are held horizontally against the substrate, folded flat over the back, or curled around the body."
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"Each butterfly begins life as an egg" — the first of four life stages — according to Bailowitz and Danforth. Typically, some days after an egg is laid, a larva, or caterpillar, hatches, beginning the second stage of life. It feeds voraciously on its host plant and grows rapidly, shedding its skin, or "molting," several times. At length, the caterpillar seeks a hiding place, where it "pupates," or covers itself in a protective envelope called a "chrysalis." Now, in the third stage of its life cycle, it begins, from within the envelope, its astonishing transformation to adulthood. After a week or more, the butterfly splits open its envelope and emerges essentially fully grown, the beginning of its fourth stage. Fluid flows into veins in its wings, straightening out the crumples of confinement. Usually within an hour, the new butterfly takes flight.
While dining on the nectar of nearby blooms — utilizing its proboscis, which it uncoils and uses like a straw — the butterfly also turns to the serious business of renewing the species. The male — typical of the gender — tries to attract as many females as possible. Or it may gather with buddies to "puddle," using its proboscis to sip water from moist soil much as if it sipping beer at the local pub. (Apparently, suggests Tom Eisner in For Love of Insects, the puddling male is gathering sodium, an element essential to the reproductive process.) The female — typical of the more responsible gender — begins to search for host plants, identified by chemical and visual cues, to lay her eggs, which may total several hundred. The adult butterfly, depending on the species and circumstances, may live for several days to some months.