E.E.E.E.K!–Why Your Zoo Should Display Live Arthropods
Randy C. Morgan, Associate Curator of Entomology
Cincinnati Zoo and Botanical Garden
This paper offers and briefly discusses five great reasons why your zoological institution should exhibit live arthropods. Exemplified by the acronym E.E.E.E.K!, these are (1) Ecological dominance, (2) Educational value, (3) Economic practicality, (4) Emotional appeal, and (5) Keeping can be easy! From “EEEEK!” to E.E.E.E.K!: Arthropods are Earth’s dominant and ecologically most important animal group. Ironically, these “creepy-crawlies” also tend to be under appreciated, maligned and feared, probably because most people lack basic knowledge and distrust creatures that appear fundamentally different than themselves. When crossing arthropod paths, the unenlightened often squeal “Eeeek!” or, worse, respond with lethal force. By considering and strategically employing E.E.E.E.K!, your zoological facility has an opportunity to positively introduce your visitors to the little animals whose vital actions make life possible for higher plants, animals and humans.
What the Heck Are Arthropods?: Arthropods are invertebrates comprising the Phylum Arthropoda. All members of this major taxonomic group share two traits: (1) jointed or segmented appendages, which include legs, antennae and mouthparts, and (2) exoskeletons or outer, hard, protective, chitinous skeletons. The arthropods are further subdivided into five great taxonomic classes: (1) Diplopoda or millipedes, (2) Chilopoda or centipedes, (3) Arachnida or spiders and kin, (4) Insecta or insects, and (5) Crustacea such as lobsters, shrimp and crabs.
An organism’s impact on its environment, whether positive or negative, is directly related to its abundance. To quantify abundance, ecologists employ two useful measures, simply defined as follows: (1) Biodiversity: the number of species (types of organisms), and (2) Biomass: the dry mass (weight) of species or organisms. These measures can be applied to all living organisms (e.g., bacteria, protozoans, fungi, plants, animals) or specified taxa. Since zoos primarily exhibit animals, we will focus on these relatively familiar creatures.
Arthropod Biodiversity Rules: The Animal Kingdom is represented by at least 30 fundamental groups, called phyla (singular: phylum), together containing over one million known or scientifically described species. In terms of relative biodiversity, one group predominates, the Phylum Arthropoda. This massive phylum claims about 874,400 described species or roughly 84% of Earth’s total animal biodiversity!!!
The next two largest phyla, Molluska (e.g., clams, snails, octopi) and Chordata (e.g., all vertebrates, tunicates, lancelets), are miniscule in comparison, comprising only about 50,000 and 48,000 species, respectively. Notably, the vertebrates (i.e., mammals, birds, reptiles, amphibians, fish) represent less than 5% of all known animal species.
The great arthropod Class Insecta alone contains over 751,000 described species, or about 72% of all known animals. Even more incredibly, recent work by Smithsonian entomologist Terry Erwin suggests that there may actually be 1030 million or more insect species awaiting discovery and scientific description! Erwin is systematically surveying one of Earth’s last frontiers, high above the ground in rain forest canopies, and has radically altered our perceptions of insect abundance, moving well towards the insects’ favor. In other words, it seems possible that over 99% of all animal species on Earth are insects, and the vast majority of these live in tropical rainforest treetops, and are still unknown to science!
Arthropod Biomass–A Real Heavyweight: Let’s turn our attention for a moment to just the terrestrial or land-dwelling animals. If we add together the weight for all large mammals, including elephants, rhinos and hippos, smaller vertebrates such as birds and lizards, and invertebrates, we find that arthropods comprise over 85% of this group’s total biomass. Again, insects claim the lion’s share! Amazingly, ants and termites alone each comprise about 1/8 of the total terrestrial animal biomass, indicating that these highly social insects are some of the Earth’s most ecologically significant and impactful animals!
Since insects tend to be relatively small organisms, they must occur in huge numbers to command such biomass. At any given moment, there may be a million trillion (1,000,000,000,000,000,000) of these six-legged animals active on Earth’s land masses! While most arthropods are terrestrial or dwell in fresh-water habitats, one major exception is the predominantly sea-dwelling crustaceans. Some forms, such as the tiny shrimp-like krill, at times multiply into vast ocean-surface blooms with equally tremendous biomass.
Thank Goodness for Arthropods: “So important are insects and other land-dwelling arthropods that if all were to disappear, humanity probably could not last more than a few months. Most of the amphibians, reptiles, birds, and mammals would crash to extinction about the same time. Next would go the bulk of flowering plants and with them the physical structure of most forests and other terrestrial habitats of the world. The land surface would literally rot.” (quote by Harvard conservationist Edward O. Wilson).
Arthropods are the bulk of the supporting foundation for most food webs (which are ultimately based on plant productivity). Examples include the countless plant-feeding insects in terrestrial communities and the multitude of ocean krill. Many larger predatory vertebrates eat insects and other arthropods directly, or indirectly by consuming animals that include arthropods in their diet.
Higher plants, especially flowering plants, are completely dependent on arthropods. Soil structures supporting natural and agricultural plant communities are created, maintained and fertilized by arthropods and other organisms. Armies of small decomposers quickly break apart organic matter into constituent nutrients, making these available for plant utilization. Burrowing arthropods loosen and turn soils, improving aeration and drainage. Numerous wild and domesticated plants are pollinated only during visits by bees and other flying insects. Often these same plants are protected from pests by the actions of beneficial arthropods, such as predatory and parasitic insects.
Any discussion of arthropod importance must include the highly social insects: all ants, termites, and some bees and wasps. Their populous, efficiently organized colonies, coupled with this group’s extreme biomass, have overwhelming ecological impact. Ants are the principal predators of other land invertebrates, shaping terrestrial food webs and the life they support. Leaf-cutting ants alone are the dominant herbivore in Neotropical habitats. To nourish their mutualistic fungus gardens, they cut more plant material than all other animal groups combined; native plants adapted to the ants’ pruning respond with accelerated plant growth. Termites are vital components of tropical systems, quickly decomposing dead plants and recycling nutrients back into the standing biomass. Both ants and termites improve soil
aeration and drainage, and in this capacity are far more important than earthworms. And while honeybees are well-known plant pollinators, stingless bee colonies perform most of this valuable service in the tropics.
Obviously, many arthropods do negatively impact people. Some bite, sting or spread debilitating or deadly diseases. Others attack our crops, livestock, pets and homes. Even so, humans tend to dwell on and disproportionally accentuate the harm caused by arthropods. In reality, all adverse effects combined are relatively minor compared to arthropods’ beneficial actions.
Don’t Miss the Bug Picture: Vertebrate animals historically have been and continue to be the mainstay of American Zoo & Aquarium Association (AZA) member institutions’ public displays and educational programs. Recall that all vertebrates belong to a just single phylum, Chordata, which rather poorly represents Earth’s animal life in terms of biological diversity and ecological significance. The arthropods’ story needs to be told, for these animals are the ecological basis of any tale about vertebrates.
As we strive to accurately depict the living world to our visitors, zoos and aquariums must incorporate more arthropods into their exhibits and educational initiatives.
Educational Toolbox: Live arthropods are the premier organisms for teaching fundamental ecological principals. A small collection can easily be maintained, transported and used interactively to demonstrate basic biological concepts such as ecological specialization, adaptation, symbiosis (parasitism, commensalism, mutualism), predator-prey relationships, camouflage and mimicry, development, metamorphosis, and behavior ranging from solitary to highly social. Arthropod versatility can be incredible; for example, consider the common fruit fly. This tiny insect can be readily reared in jars and fed to small predators, or employed in simple classroom experiments and lessons in genetics and evolution!
Conservation-Education–a Little Help for Our Friends: Unfortunately, like other organisms, arthropods can and do become endangered and go extinct, often in association with widespread habitat destruction. For example, rampant tropical deforestation eliminates locally specialized flora and fauna; at least several dozen and possibly many more insect species go extinct daily! Most disappear without ever being discovered or named, much less studied. Besides the destruction of important ecological systems, the loss of potential bio-pharmaceuticals and genetic material for bioengineering is staggering. In the United States, extreme habitat alteration has probably caused the extinction or endangerment of countless invertebrates, including many arthropods. The fifty or so insects, crustaceans and arachnids listed in the Endangered Species Act are likely the mere tip of the iceberg.
Given arthropods’ overwhelming diversity, only an insignificant proportion of threatened or endangered species could ever be managed in zoos and aquariums. Unquestionably, the best way to conserve this precious heritage is habitat preservation supported by public education and awareness programs, setting the stage for zoological institution involvement.
To date, relatively few arthropod species have been assisted by AZA member institution field conservation programs. Notably, the Roger Williams Park Zoo works with the endangered American burying beetle (Nicrophorus americanus), and the Toledo Zoo champions the Karner blue butterfly (Lycaeides melissa samuelis). Both institutions are breeding animals for reintroduction to the wild in conjunction with the U.S. Fish & Wildlife Service. These efforts have generated significant publicity and funding for the participating zoos. Similarly, the Memphis Zoo supports field research on imperiled tarantulas (Brachypelma spp.), yielding information relevant to captive management and conservation.
Jump on the Bugwagon: In 1978, the Cincinnati Zoo and Botanical Garden opened the World of the Insect (Insectarium), the first large-scale exhibit of its kind in North America. This insect zoo within a zoo displays approximately 100 live arthropod species and representative insect-eating vertebrates, all in naturalistic enclosures reflecting basic ecological relationships. From opening to present, visitor draw and media attention have been outstanding, and have more than justified the exhibit’s initial monetary cost of $1.5 million.
Shortly thereafter, the San Francisco Zoo opened its popular Insect Zoo, and more recently both the National Zoo and St. Louis Zoo presented important exhibits featuring invertebrates, all encouraging the public to see, experience, and learn about biodiversity. Over the years, a host of additional institutions have incorporated at least some arthropods into their displays, such as adding leaf-cutting ants and butterflies to rainforest theme exhibits. Major live arthropod exhibits open soon at the St. Louis and Audubon Zoos.
More Bang for Your Bug: Insect zoos, butterfly houses, aquariums, and rainforest exhibits, all featuring arthropods, are sprouting up ever more frequently in the United States and around the world. Modern zoos and aquariums are taking a fresh look at this exciting animal group. Many institutions are discovering that live arthropods not only make captivating public educational displays, but also make good economic sense. For a given amount of money, an organization can build, house and display a few large vertebrates, or numerous species of smaller arthropods, each with a fascinating and ecologically important story to tell. Which group would you choose?
People often react emotionally to arthropods. Depending on observer mindset, arthropods may be perceived as beautiful or ugly, attractive or repulsive, wonderful or disgusting, beneficial or pests, harmless or deadly, just to name a few.
Hook `Em and Reel `Em In: Emotional reactions of all kinds can be used to briefly capture visitor attention for educational message delivery. Almost everyone loves seeing colorful butterflies or touching amazingly camouflaged leaf insects. These animals can be highly effective public relations ambassadors, positively introducing humans to the arthropod world. Negative emotions can also be exploited. For example, most people hate mosquitoes and other painfully biting flies. But turnabout messages emphasizing that these small flying insects are essential food for many beautiful songbirds can begin to change visitor perspective towards appreciation, and hopefully acceptance.
Impressive Little Olympians: Zoo visitors can be enthralled by arthropods’ impressive physical feats. The ultimate gymnasts, fleas jump over fifty body-lengths with a single bound! Individual ants can lift and carry over thirty times their own body weight, and with team effort, can drag home items a thousand times heavier! Dragonflies hover effortlessly, shoot forward, backwards or dive sideways with amazing dexterity. Many aquatic insects have the best of all worlds and are equally at home swimming underwater, crawling on land, or flying through the air! Some tropical termite queens, swollen to the size of small sausages with hyperactive ovaries, lay thousands of eggs daily for up to fifty years! Comparing or extrapolating arthropod and human capabilities would make a fascinating exhibit theme for an Olympic year.
Seven Million Wonders of the World: Catch visitor attention with arthropods actively exhibiting intriguing or unusual behaviors. Winding trails of leaf-cutting ants tirelessly carrying colorful leaf and flower fragments high overhead are amazing, then to learn that the ants use these to farm fungus gardens–Fantastic! Spiny brown stick insects hanging from branches, swaying back and forth, portraying dead twigs blowing in the wind–Bizarre! Especially appreciated by female zoo visitors are male giant water bugs covered with eggs laid on their backs by their mates, grooming and protecting their brood–What wonderful dads! Superbly adapted to the water world, aquatic bugs carrying air under their wings like tiny SCUBA divers, or breathing surface air through long snorkel-like siphons–Fantastic!
Honeybee workers energetically performing the waggle dance, communicating food distance, direction and desirability to their nestmates–Incredible! And bird-eating spiders? You’ve got to be kidding!
Sex and Violence Sells!: Anything remotely related to reproductive behavior and bodily injury commands attention! If you doubt this truth for a second, take a closer look at today’s offerings from the news and entertainment industries. Exploit sexual content! Our visitors enjoy seeing and are curious about copulating insects that commonly “do it” on display. Some stick insects, such as the Florida spitting devil (Anisomorpha buprestoides), are marathon maters and literally copulate for days on end!
And isn’t it interesting to learn that queen leaf-cutting ants (Atta spp.) take only one nuptial flight, selectively mate with up to twenty of the strongest-flying male suitors, store over 300 million viable sperm, then shed their wings and settle down to a dozen or so years of egglaying?
Like Luke Skywalker, people are simultaneously repulsed by and drawn to the “Darkside.” Zoo visitors stop in their tracks when they see praying mantids snag and gobble hapless crickets or, better yet, their mantid mates! What an opportunity to teach visitors that mate cannibalism can be a beneficial reproductive strategy for all concerned: the short-lived male provides nutrients for the developing eggs he just fertilized. People are fascinated with creatures perceived as harmful or deadly, such as large hairy tarantulas, black widow spiders, and giant scorpions. Many visitors are surprised to learn that tarantula bites are not fatal but barely venomous, that large emperor scorpions are among the safest of all zoo animals to work with, and that virtually no one, especially in modern countries, dies from “deadly” black widow spider bites.
KEEPING CAN BE EASY!
Given arthropods’ tremendous diversity, it is not surprising that some types are much easier to keep or breed than others. At one extreme are species such as cockroaches, highly generalized scavengers which often thrive and reproduce under crowded conditions. At the other end of the spectrum are species with highly specialized lifecycles or environmental requirements, such as host-specific parasitoids and herbivores, thus more difficult to maintain.
Don’t Reinvent the Wheelbug: There are millions of arthropod species worthy of public exhibit. Before getting started, network with other institutions to learn which species work well in captivity, and what livestock is available from institutional surplus and commercial dealers.
Think Globally, Keep Locally: Many showy exotic insects are attractive display candidates, but often require U.S. Department of Agriculture (USDA) permits to import or hold, especially if they are plant feeders such as walking sticks. This means that your institution will have to meet minimum physical containment guidelines for these species. Alternately, there are many interesting native insects that may not require permits, or have simple permitting requirements. If in doubt, check with your State and Federal regulatory agencies.
Simple Arthropod Picks: There is an interesting array of non-insect arthropods that are extremely easy to keep and display in small enclosures. These include tarantulas and orb-weaving spiders, scorpions and vinegaroons, centipedes and millipedes, and various terrestrial, freshwater and marine crustaceans. All are predators or scavengers, thus USDA permit-free. And most tend to be long-lived animals, reducing the need for captive breeding.
Relax and Breed Easy: Many insects have short lifecycles, thus must be routinely propagated to ensure sufficient display populations. Some species are very time and energy demanding to maintain (e.g., butterflies). But those undergoing gradual metamorphosis are often easy to rear since the nymphal stages and adults generally have the same nutritional and environmental needs. This group includes various roaches, crickets, katydids, grasshoppers, assassin bugs, and aquatic bugs such as water striders, backswimmers and giant water bugs.
Embrace High Society: Active colonies of highly social insects are endlessly fascinating to observe, and ecologically important study animals. Most ants require significant hands-on experience to keep successfully, with one important exception, the predominantly tropical leaf-cutting ants (Atta spp.). These are among the most sophisticated of all social insects, yet easy to keep in captivity. Similarly, the North American giant dampwood termite (Zootermopsis angusticollis) is simple to rear and display. Honey bee (Apis mellifera) observation hives are always popular and fun to interpret, but work best if managed by experienced beekeepers.
WHY SHOULD YOUR ZOO DISPLAY LIVE ARTHROPODS?
The answer, of course, is E.E.E.E.K! Arthropods are (1) Ecologically dominant and vitally important animals, (2) Educationally valuable public displays and teaching tools, (3) Economically practical to maintain, (4) Emotionally appealing to zoo visitors, while (5) Keeping these versatile little creatures can be easy! What more could zoo and aquarium professionals possibly ask for?
ACKNOWLEDGMENTS: The Cincinnati Zoo and Botanical Garden supported this work. This paper evolved from an invited demonstration given to the Conservation Educators’ group at AZA’s Schools for Zoo & Aquarium Personnel in February 1999. Portions of the text were adapted from the Invertebrate Biology Monograph prepared for the Applied Zoo & Aquarium Biology course. Kathy Beil-Morgan and Milan Busching offered helpful manuscript comments.