(With apologies to Gertrude Stein, who said in her 1913 poem Sacred Emily that “Rose is a rose is a rose.”)
The population of insects in the desert basins and mountain ranges of the Southwest falls far short, in terms of sheer numbers, of that in many other parts of the United States, for instance, in the densely vegetated and humid estuaries along the Gulf Coast. The diversity of species across the Southwest, however, may equal or exceed that of any place else in the country. As Floyd G. Werner said in Insects of the Southwest, which he co-authored with Carl Olson, “The Southwest has a concentration of diversity that is unbeatable in the United States.”
The hundred thousand or more of insect species in the Southwest amount to a small percentage of the possibly 10 million species throughout the world. The ever changing mix within our various insect communities and the variability among the species, however, reflect ecological and environmental conditions that range from vast hot desert basins (where temperatures can exceed 120 degrees Fahrenheit) with sparse vegetation or almost barren sand dunes; to widely separated river bottoms with dense shrub and thick woodlands; to mountain slopes and valleys with pygmy woodlands and park-like forests; to towering peaks (where temperatures can fall to 40 to 50 degrees below zero) with subalpine forests and alpine tundra. The insects have adapted to every ecological niche in the Southwest, making their homes in the rocks, the soils, the air, the plants, the animals.
They vary almost unimaginably in terms of size, form, color, range, habitat, diet and environmental roles and in almost science-fiction life cycles and behaviors, but for all their differences, they are bound together by certain common characteristics. Every species has a head, a thorax and an abdomen. The head has eyes, antenna and the mouthparts. The thorax, or middle body segment, bears wings and six jointed legs. The abdomen contains the heart, the digestive tract and the reproductive organs. Every species has an exoskeleton that encases vital organs. A few examples suggest the breadth of the diversity.
“Of all the bugs, the aphids are probably the most interesting,” William Atherton DuPuy said in his Our Insect Friends and Foes, first published in 1925.
In the Southwest, the aphids, or “plant lice,” comprise a number of species that come in a range of sizes (all small, from one to three sixteenths of an inch in length, according to Werner and Olson) and in a variety of colors (from green to bright yellow to black to brown). Soft and pear-shaped, the typical aphid has a distinctive pair of cornicles, or “honey tubes,” protruding from the rear of its abdomen. When called to move, perhaps due to overcrowding or declining plant forage, the aphid may dress itself in wings, which will take it to new fields.
The aphid, well represented throughout the Southwest, often gets very choosy in selecting the plant on which it will feed. A yellow and black species, for instance, lives solely on milkweeds or oleanders, said Werner and Olson. Another species may dine just on your roses or another of your garden plants. “The brown aphids that make a shiny mess under arbor vitae trees [a species of conifer] can’t even live on the related junipers,” said the authors.
In feeding, the aphid inserts its straw-like proboscis, or “bill,” through the plant skin, and sucks up the fluid, causing leaves to shrivel and, sometimes, the plant to die. Because the plant fluids lack amino acids essential to life, the aphid calls on a bacterium, which lives within specialized cells, to provide supplementary nutrients, an insect’s way of taking vitamins.
Prodigiously reproductive, the adult female aphid of the early spring may carry within her body not one, but two, generations, or a pregnant daughtera kind of biological telescoping of the reproductive process, with no need for males. An aphid population, all female from spring into the summer, can explode almost overnight. The male aphid finally makes an appearance in the fall, as the sunlight wanes and the temperatures fall. It and the female mate. The female now produces an egg that can survive through the winter, yielding a larva that renews the aphid’s reproduction cycle come spring and summer.
Fortunately, aphids serve as a banquet for ladybird beetles and their voracious larvae as well as for parasitic wasps and aphid lions. Otherwise, aphids would soon engulf us all.
Strangely, the aphid, secreting honey dew from its cornicles, also serves as a kind of milk cow, or more aptly, a “honey cow,” for ants. DuPuy said, “Ants follow these aphids about and lap up this honey. They even have flocks of them and milk them regularly.”
The cochineal, or “crimson,” scale has played what is perhaps a unique role for insects on the world stage, having parts in textile manufacturing, territorial conquest, international commerce, cosmetic production, food processing and even science and art.
It seems too small a creature for such an outsized task. The female cochineal insect, colored by red pigment, measures only some one-sixteenth to one-quarter of an inch in length; the male measures about half the female’s length. She has neither wings nor legs; he has both. She has the shape of an engorged tick; he has more the look of a typical insect, with the addition of two distinctive filaments extending from the rear of his abdomen.
The cochineal covers much of the lower elevations in the western United States and Mexico, according to the Arizona Wild Flowers Internet site. It feeds almost solely on the pads of selected prickly pear cacti species. Like the aphid (a related insect) the female drives her tubular proboscis through the cactus skin, where she will remain affixed for the rest of her life, sucking out the juice. Simultaneously, she produces a white, waxy, fungus-looking coating that will help protect her from predatory insects and birds and shade her from the desert sun. She nevertheless sometimes fall prey to a rare carnivorous caterpillar and more commonly, to our good friend, the ladybird beetle. Over time, a heavy cochineal infestation can kill its resident plant.
As she feeds, the immobile female cochineal produces eggs beneath her abdomen. When the eggs hatch, the legged juveniles, females and males, called “crawlers,” make their way to the edge of their home cactus pad. Wingless females produce long, ethereal filaments, which lift the insects on the desert wind. Some descend onto new host prickly pear cacti, where they will breed, make a new home, set a new dining table, molt and shed their legs, their traveling life over and done. Winged males take flight, searching for mates so they fulfill their role in nature’s plan. They die within a few days.
As the Spanish discovered when they conquered Mexico in 1521, the cochineal scale insect, when crushed, yielded a supreme scarlet dye, which the Aztecs had long used in the production of exquisite textiles. The dye would become an added incentive for Spain in its Mexican conquest. The cochineal the Spanish held the source of the dye secret for years produced a major cash export from Mexico, second only to silver. Over time and across Europe, it would, according to Werner and Olson, bring the color scarlet to royalty’s garments, military uniforms, national dress, cosmetics, various foods, and even Michelangelo’s palette. It may have been used in the cloth that Betsy Ross used in making the red stripes for the first flag of the United States. The cochineal still serves as the source of the dye that microbiologists use to stain slide specimens, although it pays a heavy price for the privilege. Some 70,000 cochineal insects are required to manufacture a single pound of the dye.
The blister beetle named for its ability to exude from its joints a liquid that causes painful blisters on your skin ranks close to the top of the list as the insect world’s most clever and odious imposters, even if it is often colorful and relatively innocent looking.
According to Donald J. Borror and Richard E. White, A Field Guide to the Insects of America North of Mexico, the typical blister beetle has an elongated and pliable body. It measures about a half inch to an inch and a half in length. The beetle, says New Mexico State University entomologist, Charles R. Ward, “Blister Beetles in Alfalfa,” has thread-like antenna, non-bulging compound eyes, a bowed head, and relatively long legs. “Primary body colors,” said Ward, “include black, brown, or gray; different species have spots or stripes of yellow red, brown orange, black, or white,” depending on the species.
Of the more than 300 species that occur in the United States, several dozen make their home in the Southwest, where the adults feed, sometimes voraciously, on both wild and cultivated plants, often favoring mesquites. One of the Insects of the Southwest authors said, “I have seen stripped [by blister beetles] trees in a straight line several hundred feet long.” If inadvertently harvested and bailed in large numbers with alfalfa, the blister beetle, which contains a toxic chemical compound called “cantharidin,” can poison domestic animals, especially horses, that eat the hay.
In some species, the blister beetle larvae prey on the eggs of grasshoppers, actually imposing some control on a historic pest. In other species, newborn larvae, called “triungulins,” pack themselves together by the hundreds in a single mass that mimics and even smells like! a female solitary bee, according to a year 2000 San Francisco State University news release, “‘Spanish Fly’ Beetles Use Sex and Subterfuge to Infiltrate Bee’s Nests.” Collectively, with the precision of a military band, they march to the tip of their host plant stem, where they pose provocatively as a single female bee, displaying a phony sexuality, luring lusty male bees. They quickly attach themselves to a foolish male when he tries to mate with them. They transfer to various females when the male tries to couple with more rewarding mates. They cling to the unwitting females for a free ride to the bees’ nests. “Then,” said DuPuy, “showing no gratitude for the transportation furnished, this vicious little creature alights, crowds it way into a cell which the bee has arranged for its young, eats her larva there and feasts for growing days on the food that has been provided for that larva.”
The assassin bug’s aliases for instance, conenose bug, walapai tiger, bed bug, wheel bug, thread-legged bug, kissing bug reflect the insect’s multiple personalities, making it a perfect villain for a James Bond film. Depending on the species, this bloodthirsty bug may prey not only on other insects but also on reptiles, birds or mammals, including humans.
Typically, an assassin bug, which may look almost armor plated, like a medieval knight, measures a fraction of an inch to an inch and a half in length. Its color ranges from brownish to black. It has a generally oval, but sometimes a considerably elongated, shape, according to Borror and White. It has antenna with four segments. It has a three-segmented tube-like beak that it folds into a groove beneath its throat. It has thickened forelegs that it snaps together like spring-loaded clamps to catch insect prey. Threatened by other predators such as certain reptiles or birds, some assassin bug species defend themselves by using their beaks to squirt their venom, from a foot away, at their attacker’s eyes and nose, causing extreme irritation. If its stream strikes a human’s eyes, it can cause temporary blindness.
Widely distributed across the Southwest, the assassin bug that preys on insects tends to hang around foliage, and the species that prey on vertebrate animals may invade burrows, nests, dens and human bedrooms. The female lays her eggs in the fall, primarily in secreted crevices and cracks. The nymph hatches in the spring, looking much like a miniature adult. After several molts, it emerges as a full-grown assassin bug, ready to ply its full trade.
The species that prey on insects may stalk and attack or simply ambush their victims. The assassin bug drives its beak like a dagger into its victim’s body, injecting “a very toxic, or poisonous, liquid that affects the nerves and liquefies the muscles and tissues…” according to the From Amazing Insects Internet site. “…prey many times their size can be quickly overcome. Once the insides of the prey are turned into a liquid, the assassin bug uses its [beak] to suck out the liquefied tissues in much the same way we use a straw to drink a milkshake!” The assassin bug’s toxin can kill a much larger insect in a matter of seconds. It discards its victim’s carcass with disdain. The assassin bug may also deliver a painful bite, in self defense, if carelessly handled by a human.
The species that prey on the blood of vertebrate animals feed not only on wildlife (especially pack rats) but also on domesticated animals and pets, and, sometimes, they may help themselves to human blood. The assassin bug usually comes under the cover of darkness, stealthily, invading a person’s bed, looking for exposed flesh, usually the face, especially the tender flesh around the eyelids, ears or lips (ready to deliver an ominous “kiss”). In a Utah State University Extension Entomology fact sheet, insect diagnostician Alan H. Roe, said that as an assassin bug delivers a bite, it injects a anesthetic, rendering the wound virtually painless, and it injects an anticoagulant, assuring free blood flow. In the Dermatology Online Journal, Rick Vetter said that the insect, typically, would feed for 8 to 15 minutes. It may cause an especially sensitive person to suffer symptoms such as violent itching, breathlessness, nausea, heart palpitation and even unconsciousness, said Roe. In Latin America, the bite sometimes leads to Chaga’s disease, a form of sleeping sickness, although that is rare in the United States. The assassin could clearly be a villain worthy of James Bond.
The aphid, cochineal scale, blister beetle and assassin bug provide a snapshot of the variability in the world of insects, but, in the end, they deliver no more than the briefest glimpse of a strange world. They tell us nothing of whole other families of insects. Butterflies, for instance, the swallowtails, bring a whole other dimension, with an ethereal beauty, to the Southwest. Social insects the ants, termites, honeybees and wasps draw the fascination of biological scientists and sociologists with an orchestrated and disciplined lifestyle. Twig-like, three-inch-long walking sticks, so thin that they sometimes bear names like “devil’s walking stick” or “devil’s knitting needle,” may strip the leaves from trees and issue a venomous spray at its would-be attackers. The praying mantis, a three-inch, powerful insect, ambushes victims and eats them alive, “like a stalk of celery,” said Werner and Olson.
In the Southwest, tens of thousands of insects have been identified and classified by biological scientists, but only a fraction of those have been studied closely. Moreover, tens of thousands more await identification and classification. The richness of life in the insect community of the Southwest the diversity of sizes, forms, colors, ranges, habitats, diets and environmental roles is a story still unfolding, with many chapters still to unfold.
It gives a whole new perspective to the notion that an insect is just an insect is just an insect.
My thanks to Jana McFarland, New Mexico State University graduate student, for her help in identifying the insects in the photographs.
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