'

Braconid wasp

Invertebrates are without a backbone or skeleton mussels. Indirectly, humans benefit from invertebrates that containing bones. Invertebrates range in size from are essential food for fish, birds, and other microscopic to 59 feet long and weighing nearly a ton, like that we harvest or simply enjoy watching. As pollinators the giant or colossal squids. While vertebrates – animals and decomposers, invertebrates are necessary for with a backbone – are better known, they are greatly reproduction and growth, and therefore provide food and outnumbered by invertebrates in diversity and sheer sources of shelter, fuel, and medicine that we need to survive. abundance. Most living things are invertebrates with more than 1.25 million species globally. In Iowa, for example, there are more than 2,000 species of moths, while the most Arthropods have the greatest number of species among diverse group of Iowa vertebrates, birds, have only 300-400 all groups of invertebrates. Included in the arthropods species that live or migrate through our state. Invertebrates are several classes of familiar animals, including , are an incredibly diverse group of animals that can be found arachnids (spiders, , and ticks), (lobsters, everywhere you might look in Iowa. crayfish, and shrimps), millipedes, and centipedes, all of Invertebrates are also important to our survival; we depend which have many species living in Iowa. Despite their on services these animals provide. Humans consume diversity, arthropods all share common characteristics that some invertebrates directly as food, like crayfish and distinguish them from other major groups of animals.

Table 1: Five major taxonomic groups of invertebrates found in Iowa.

GROUP () EXAMPLES ENVIRONMENT PHYSICAL CHARACTERISTICS Body is segmented and covered Insects, spiders, mites, ticks, Arthropods (Arthropoda) Freshwater, terrestrial by an exoskeleton made of ; crustaceans, millipedes, centipedes paired, jointed appendages. Wormlike body is soft and Segmented (Annelida) , freshwater, terrestrial segmented Body is soft and unsegmented with a muscular foot; snails and Mollusks () Snails, slugs, bivalves (ex. mussels) Freshwater, terrestrial slugs have tentacles on their head; mussel body is enclosed in a shell Freshwater, terrestrial, inside a host Wormlike body is smooth, round, Roundworms (Nematoda) , hookworms body and unsegmented

Flatworms, flukes, tapeworms, Freshwater, terrestrial, inside a host Wormlike body is flat, and usually (Platyhelmintha) planarians, or turbellarians body unsegmented taxonomic tree. Table 2: Five major classes of Arthoropods found in Iowa. Animals ARACHNID CLASS GROUP MILLIPEDE CLASS CENTIPEDE CLASS Insects Spiders, mites, ticks Crayfish, sowbugs (isopods), Millipedes Centipedes cladocerans

Vertebrates Invertebrates

Protozoa Flatworms Mollusks 3 body parts: Head, thorax, 2 body regions: 2 body regions: Cylindrical or flattened, Flattened, elongated body, abdomen Cephalothorax, abdomen Cephalothorax, abdomen elongated body, 20+ body 15+ body segments segments 3 pairs of segmented legs 4 pairs of segmented legs At least 5 pairs of segmented 2 pairs of legs per 1 pair of legs per segment legs segment Amoeba Arthropods Nematodes 1 pair of antennae no antennae 2 pairs of antennae 1 pair of short antennae 1 pair of large antennae

Planarian 0, 2, or 4 wings no wings no wings no wings no wings >1,000,000 species globally 75,500 species globally 67,000 species globally 10,000 species globally 8,000 species globally

Millipedes and Arachnids Crustaceans Insects Centipedes Land snail nematodes

Earthworm

Crayfish Common eastern American giant Zebra jumping spider bumble bee millipede

Arthropods have pairs of jointed appendages, resembling There are 15 groups or classes in the phylum, human legs and arms. It is the jointed legs that gives this but only the five major classes commonly observed in Iowa group their name; arthro is Greek for joint and pod refers are presented here. Classes differ based on a few key to feet and legs. Arthropods also have an exoskeleton, characteristics listed in Table 2, including: made of a special material called chitin, which covers the 1. Number of body regions outside of their body. They have an open 2. Number of legs with no network of , arteries, and , and a 3. Number of antennae simple heart completely unlike a human heart. Rather than having a spinal cord like humans, they have a nerve cord that runs down the front of their bodies which serves a similar role as our . Arthropod breathing is accomplished either with or through a system of holes in the exoskeleton called spiracles and tubes that move air from spiracles to organs called tracheae. These differences from vertebrates might lead to the mistaken conclusion that this is a small, exclusive group of creatures. However, arthropods contain approximately three-fourths of all the world's species, numbering in the millions compared to the roughly 60,000 species.

Soldier fly Table 2: Five major classes of Arthoropods found in Iowa. INSECT CLASS ARACHNID CLASS CRUSTACEAN GROUP MILLIPEDE CLASS CENTIPEDE CLASS Insects Spiders, mites, ticks Crayfish, sowbugs (isopods), Millipedes Centipedes cladocerans

3 body parts: Head, thorax, 2 body regions: 2 body regions: Cylindrical or flattened, Flattened, elongated body, abdomen Cephalothorax, abdomen Cephalothorax, abdomen elongated body, 20+ body 15+ body segments segments 3 pairs of segmented legs 4 pairs of segmented legs At least 5 pairs of segmented 2 pairs of legs per 1 pair of legs per segment legs segment 1 pair of antennae no antennae 2 pairs of antennae 1 pair of short antennae 1 pair of large antennae 0, 2, or 4 wings no wings no wings no wings no wings >1,000,000 species globally 75,500 species globally 67,000 species globally 10,000 species globally 8,000 species globally

Class Insecta Insecta is the largest class of arthropods and they all have Iowa insects, like this worker an exoskeleton and jointed legs. In Iowa, insects come in ant, all have three body Antennae all shapes and sizes, from tiny gnats to the 6-inch cecropia segments–a head with antennae and , a thorax to which moth, but they all have the following combination of specific attaches three pairs of legs and characteristics that have specialized functions. The head has an abdomen. Head the mouth parts, eyes, antennae, and other sense organs, and the . The antennae are used primarily to detect odors and chemicals in the environment and to physically feel their Thorax environment for navigation purposes. The thorax carries the means of travel: three pairs of legs and the wings, if present. Insects that possess wings most often have two pairs There are 15 groups or classes in the arthropod phylum, although some, like flies, have only one pair of wings. Some but only the five major classes commonly observed in Iowa insects such as fleas and worker ants don’t have wings at Abdomen are presented here. Classes differ based on a few key all. Finally, the abdomen contains the internal systems characteristics listed in Table 2, including: necessary for digestion, breathing, and reproduction. 1. Number of body regions Class Arachnida Arachnids, like this zebra jumping spider (Salticus 2. Number of legs The class Arachnida includes spiders, mites, ticks, scorpions, scenicus), have their head 3. Number of antennae and related organisms and is a diverse and well-known group. and thorax fused into a There are no estimates for the number of species that can cephalothorax. They also have an abdomen and four be found in Iowa, but more than 75,000 have been recorded pairs of legs. globally. Abdomen Arachnids have only two body parts. The first body region consists of the head and thorax fused into a single structure called the cephalothorax, where four pairs of legs are attached. The second body region of the Arachnida is the abdomen. The two body regions are obvious in large spiders Cephalothorax such as the garden spider found all over Iowa. Arachnids do not have antennae or wings. Daddy-longlegs are technically separate from spiders (they are a separate order in the arachnid class). Daddy-longlegs, also called harvestmen, have the cephalothorax and abdomen fused into what appears to be a single segment. There are four pairs of segmented legs attached to the cephalothorax. Eight legs Crustaceans Although the most recognizable crustaceans are important foods for humans such as shrimp, crab, and lobster. Iowa Two pair

of antennaeTwo pairs has its own diverse set of crustaceans including crayfish, of antennae sowbugs or isopods, amphipods, cladocerans, , and ostracods. Like the Arachnida, crustaceans have Crustaceans, like this sowbug, have two body regions like the archanids two body regions; a cephalothorax and an abdomen. Cephalothorax but at least five pairs of legs and Cephalothorax Unlike arachnids, however, crustaceans have two pairs of two pairs of antennae (one pair is antennae and at least five pairs of legs. Crustaceans have very short on the sowbug). one pair of appendages per abdominal segment. What AbdomenAbdomen we generally call legs, also known as walking legs, are attached to the thorax region. Class Diplopoda Members of the class Diplopoda are called millipedes.

Each body segment has four legs (two pairs) per segment. 20+ body segments Their numerous legs are close together and short, making 20+ body segments their movements relatively slow and occurring by waves of leg movement down the body. Millipedes have many body segments with two pairs of Class Chilopoda legs per segment. Members of the class Chilopoda are called centipedes and their name translates to mean "one hundred legs," Two pairsTwo of pair s of legs though this can be an exaggeration. In fact, the number legs per segmentper segment of legs a centipede has actually varies with the number of body segments, but they always have two legs (one pair) per segment. The number of segments varies from 15-191 and is always an odd number. Legs of the first body segment are modified into venomous claws. These claws assist the predaceous centipedes in capturing prey or Flattened, Flatlongtened, body long body protecting themselves. Small centipedes, such as those Centipedes, like this house found in Iowa, are incapable of biting and are not a threat centipede (Scutigera coleopatra), to humans. have many body segments with one pair of legs per segment. SEGMENTED WORMS 1 pair of legsOne pair of legs Segmented worms or annelids, all have distinct body per segmentper segment segments, a soft body without an exoskeleton, and no legs. Two common groups of annelids in Iowa are oligochaetes and leeches. Oligochaetes Oligochaetes have stiff bristle-like structures made of chitin, called chaetae, on their body segments, although Segmented worms, these structures must often be viewed under a microscope or annelids, like this to be seen. Oligochaetes can be abundant in both , have no SegmentedSegmented exoskeleton, no legs, and terrestrial and aquatic environments. Some examples a many-segmented body. of oligochaetes in Iowa are earthworms in terrestrial environments and tubificid worms in water. Many terrestrial Wormlike, soft body earthworms found in Iowa are exotic species that were Wormlike, soft body established in the state through intentional or unintentional introduction by humans. However, at least three native species of terrestrial earthworms can be found in southern Iowa. Iowa is home to dozens of native species of aquatic oligochaetes, in addition to at least a few exotic species. Leeches Leeches have a flattened body, lack chaetae and have two Segmented suckers, one at each end of the . Leeches inhabit aquatic , where they use their suckers to attach Leeches are another to a host and feed on body fluids. There are more than 60 kind of found in species of leeches found in North America. Iowa that mostly inhabit aquatic ecosystems. SNAILS, SLUGS, AND BIVALVES Snails, slugs, and bivalves, collectively known as Mollusks, Wormlike, soft body have soft, unsegmented bodies, and a muscular foot that helps them move around. Snails and slugs, which fall into a group called gastropods, have a head with tentacles. Snails possess a shell that functions as a shelter when the is inactive or threatened by predators. This shell is Mollusks, like these terrestrial or land snails, absent in slugs. Bodies of clams and mussels, also known have soft unsegmented as bivalves, are surrounded by two shells attached together bodies and a muscular by a hinge. Historically, Iowa was home to a diverse group foot that moves them around. Many have shells of mollusks, but species diversity has declined greatly in the (snails and mussels), Muscular foot past 200 years. At least 60 species of mussels, 49 species of some do not (slugs). aquatic gastropods, and 125 species of terrestrial gastropods Soft body once inhabited Iowa. Due primarily to habitat loss and pollution, approximately 50% of our native species of aquatic gastropods and bivalves no longer occur in Iowa. Compared to most other groups of animals, terrestrial gastropods suffer very high extinction rates, and many of our native species are undoubtedly now absent from Iowa or imperiled. The Iowa Pleistocene snail (Discus macclintocki) is so rare that it is designated as in danger of extinction through the federal Endangered Species Act. The water pollution and habitat degradation that threatens bivalve populations is mainly caused by the accumulation of fine that is a result of soil erosion on river and lake beds. Another cause of population declines are non-native species such as the zebra mussel (Dreissena polymorpha). It attaches to rocks and other hard substrate and negatively affects many species of invertebrates and fishes by outcompeting them for habitat and food. Zebra mussels Zebra mussels living on the shell of a native species of mussel. even colonize shells of native bivalves, and can kill them by interfering with feeding and breathing.

ROUNDWORMS AND FLATWORMS Compared to the other invertebrates examined above, the roundworms, also called nematodes, and flatworms are much less likely to be observed. Nematodes generally have very small bodies, but are extremely abundant in soil and sediment of terrestrial and aquatic ecosystems. 1mm Most flatworms, including flukes and tapeworms, are endoparasites of humans and other vertebrates. However, aquatic species, such as planarians or turbellarians, can be found attached to or crawling on rocks. These animals are important scavengers of dead animals. They can also be predators on of snails and other invertebrates. Roundworms, like these soil nematodes, and flatworms are very small organisms. INSECT CYCLES Complete is probably more familiar to Nearly all insects develop from eggs produced by the most of us because of the familiar life-cycle of butterflies. female. The rest of the growth and development differs In this life cycle, a wormlike, immature insect is quite with different types of insects. There are three general different from its adult form. Complete metamorphosis types of life cycles or metamorphosis: ametabolous, simple consists of four generalized stages: , , , and metamorphosis, and complete metamorphosis. adult. Ametabolous insects hatch as a miniature version of the Each stage often in different habitats and has very adult and simply grow with little or no change except in different habits. Certain insect groups are so prevalent size as they enlarge from egg to adult. The common insects that they have been given special terms for their life in this group are the soil-dwelling springtails. cycle stages. For example, for moths, the term caterpillar is used for the larval stage and cocoon is the term used Simple metamorphosis has three stages: egg, nymph, and for the pupal stage. For butterflies, the terms caterpillar adult. The young, or nymphs, are very similar to the adults, and chrysalis are used for the larval and pupal stages. In but they are smaller, have no wings, and cannot reproduce. the case of flies, a larva is called a and a pupa is Nymphs are usually found in the same habitats and called a puparium. Insects with complete metamorphosis typically feed on the same food as the adults. Insect groups include , butterflies, moths, flies, midges, with simple metamorphosis include grasshoppers, crickets, mosquitoes, wasps, bees, and ants. cockroaches, true bugs, aphids, cicadas, lice, dragonflies, damselflies, mayflies, and a few others.

Egg

Egg

Adult Nymph

Adult

Two-striped grasshopper (Melanopus bivittatus) Intermediate Simple metamorphosis

Springtail (Folsomisia candida) No metamorphosis - ametabolous Egg

Larva

Adult

Pupa

Stag (Lucanus placidus) Complete metamorphosis HABITATS green darners and lay eggs on emergent Invertebrates are found in environments vegetation. Outside of the breeding as diverse as the species themselves. season however, green darners can be Some of the major factors that found in many open habitats. During determine invertebrate habitats include the fall, a segment of Iowa's population diet, mobility, seasonality, and evolution. migrates into the southern U.S. or Central Some groups lead a double life, like America, flying an average of 400 miles to dragonflies and caddisflies, spending their final destination. their larval period under water and their Some groups of invertebrates are found adult life in the sky. The small size and in This house centipede can be scary for almost entirely in aquatic habitats. Most some cases sedentary lifestyle of many homeowners, but is actually helping keep arachnids are strictly terrestrial, however, invertebrates means that often their other insects in the house in check by many species of mites are aquatic for part world can be encompassed in an area preying on them. or all of their life cycle. The aquatic mites only a few square feet in size. Others, have complex life cycles with variable especially those with wings, can cover surprisingly large habitat needs. As larvae, aquatic mites attach to insects areas. Some invertebrates are picky eaters and may eat or mollusks and feed on these hosts. Mites that parasitize only one type of food, while others are generalists and eat aquatic insect larvae may remain attached to their host almost anything, which influences where they call home. when it leaves the water. When the adult insect returns to Many invertebrates have even adapted to live alongside the water to lay eggs, these mites drop off of the insect, humans in our houses and other buildings. re-enter the aquatic , and mature into adults. The endangered Iowa Pleistocene snail (Discus Leaving the aquatic habitat is risky, but it is an effective macclintocki) is an example of an invertebrate that lives way to disperse to new habitats and can increase survival its whole life in a very small area and in a very specific of the species. habitat. This tiny snail is only found on a handful of sites in One study of human dwellings conducted in North northeastern Iowa where they inhabit Algific Talus Slopes. Carolina found that the average household contained This rare ecosystem is an area that is kept cool by cold 100 species of invertebrates, primarily arthropods. These air from underground ice reserves being released through invertebrates that have adapted to living alongside vents in the ground. This unique micro-climate is the only us include mostly harmless species like booklice, environment that can support these snails. The venting centipedes and tiny spiders. The list includes only a few keeps the slope cool in summer and above 14 degrees annoying invertebrates, such as boxelder bugs, bed bugs, Fahrenheit in winter. These snails may move as little as cockroaches and termites. One anthropod commonly 10 cm, likely no further than 18 meters in a year. encountered in Iowa homes is the house centipede, which In contrast, the common green darner (Anax junius), is preys upon insects and other arthropods. This beneficial a large, carnivorous and highly mobile dragonfly found predatory activity of the house centipede is rarely statewide in Iowa. When breeding, these large insects appreciated by a homeowner who discovers these fast- stay close to a pond or marsh where they can find other moving creatures in the bathroom or kitchen. Insect Diversity in Iowa Insects are the most diverse groups of arthropods, with possibly 4-10 million species that have yet to be discovered or classified. Even in Iowa there is still a lot to learn and discover.

We know the most about insect pests and some of the flashier groups of insects. We know less about beneficial insects such as pollinators, scavengers, and decomposers. There are as many as 100 species of butterflies in Iowa, but a small number garner the most attention. Of the approximately 2,000 species of moths, only the large, attractive species often get noticed. Dragonflies and damselflies are also fairly well documented with about 120 species. Of the 4,000 species of bees in North America, around 300 species (mostly solitary species) have been documented in Iowa. This twelve-spotted skimmer (Libellula Even with these relatively well known groups, it would puchella) is a very common sight and is one of the approximately 120 species of not be surprising to find a previously unknown species dragonflies and damselflies found in Iowa. inhabiting the state. REPRODUCTION 3. Reproductive division of labor: sterile individuals work for the benefit of a few reproductive individuals. Insect Reproduction 4. Overlap of generations: offspring contribute to colony Insects have a variety of reproductive behaviors and labor while their parents are still alive. rituals. Most insect reproduction is sexual. That is, in most species, there are females and males that produce a germ Reproduction Among Other Invertebrates (egg and , respectively). The male inseminates Among the rest of the invertebrates, we find a diversity of the female during mating, and the female often stores reproductive strategies. As in insects, crustaceans sperm in special pouches in her abdomen and fertilizes reproduce by laying eggs that in some species hatch as a eggs to produce an embryo. Eggs are deposited on a host larva that looks very different from its parents, and in other or an environment where the offspring will flourish. Eggs species hatch as a juvenile that closely resembles the adult hatch into nymphs or larvae and grow. life stage. Those that look different from their parents develop through several stages and then undergo There are some insect groups where females are capable metamorphosis during which they add body segments, grow of reproducing asexually, or without fertilization. For larger, and eventually reach sexual maturity. Most example, some aphids produce all-female generations by reproduction in other classes of invertebrates is sexual, . In some insects, such as bees, the requiring two parents. Some crustaceans, like cladocerans, reproducing female at the time of laying each egg can can reproduce both sexually and asexually. In asexual fertilize the egg or not. Unfertilized eggs become males and reproduction, a parent produces offspring on its own, and fertilized eggs become females. each offspring is a clone, or genetic copy. Many A few well-known groups of insects have fascinating crustaceans, including the common cladoceran Daphnia social behaviors. These groups include ants, termites, found in lakes and wetlands in Iowa, produce eggs that can honey bees, bumble bees, and some wasps. remain dormant for decades. These “resting eggs” allow There are four qualifications for classifying a species as populations to survive in aquatic habitats that are truly social (also called eusocial): ephemeral, or temporary, because they regularly dry up and may remain dry for many years. Such eggs remain in the soil 1. Share a common nest site. until exposure to water provides a cue for them to hatch. 2. Individuals of the same species cooperate in caring for the young.

Freshwater mussels have a fascinating life cycle that requires a fish or salamander to help during the growth of larval mussels called glochidia. 1. Males release sperm to fertilize females 2. Females release larvae 3. Larvae on gills 4. Juveniles release from fish 5. Juveniles mature in the substrate Iowa’s mussels in the Unionidae exhibit a spiders. Fishing spiders live around aquatic environments fascinating reproduction strategy. Like many other and can skate on top of the water after prey. animals, they reproduce sexually. Males release sperm Parasites are also well represented in Iowa’s into the water, which is taken in by a female that broods invertebrates. Mites and ticks range from feeding the eggs in special chambers in her gills called marsupia. on vertebrates, to plant feeders, to predatory species that The fertilized eggs develop into the larval stage called feed on other species. Many leeches are temporary glochidia, which are little more than two hinged shells parasites of vertebrates that usually do not kill their host. with the muscles needed to open and close them. When Leeches that consume invertebrate body fluids will kill the glochidia are released by the female mussel they their host and are therefore classified as predators. must attach to a fish host where they will transform into juvenile mussels. To assist in finding a host for their Some invertebrates even feed on excrement, such as offspring, the female unionid mussels have a part of the the industrious dung beetle. Dung beetles are experts at body that resembles a small fish in both appearance and recycling the waste of cattle and bison. Adults lay their movement. As the female lies on the bottom of the river eggs into dung and the larvae that hatch out then eats the or lake, this flap-like structure acts like a fishing lure dung. Some dung beetles into dung where it falls; from the shell. Once a curious fish inspects the structure others roll away a ball of dung, bury the ball, and lay an taking it for a source of food, the female releases the egg in it. Two dung beetles commonly found in pastures in glochidia into the face of the fish so they can attach to its Iowa are the colorful rainbow scarab, , gills. The glochidia remain on the fish’s gills for a period and the Carolina copris, carolinus. Both are of time, drop off, and then begin their lives as free-living “tunnelers” that excavate the soil underneath a dung pat bivalves. Freshwater mussels sometimes depend on a and bury it where it falls, without rolling it away as seen in very specific fish or salamander host such as in the case popular dung beetle videos from Africa. of the salamander mussel, whose glochidia must attach Finally, invertebrates are the most important decomposers to a mudpuppy salamander. and detritivores in both aquatic and terrestrial ecosystems. Some common detritivores on land are DIET AND FEEDING STRATEGIES nematodes, earthworms, and sowbugs, also known as Invertebrates in Iowa encompass almost all possible roly pollies. Gastropods, such as aquatic snails, actively feeding strategies and diets. They can be filter feeders, crawl and feed by using a scraping mouthpart called a parasites, parasitoids, herbivores, carnivores, omnivores, radula to remove algae, fungi, and other microorganisms and detritivores. If something is edible, there is an from rocks, logs, or plants. Oligochaetes are particularly invertebrate to eat it. Some invertebrates, like the little important detritivores. As they move through terrestrial wood satyr butterfly, only eat during one life stage, in this soil and aquatic sediment, they eat dead plant material case as a caterpillar, and take little to no nourishment as and associated microorganisms such as and an adult. fungi. Some energy and nutrients within this decomposing Not all insects eat the same things, and what an insect is material is later passed on to birds, fish, and other capable of eating is determined by the type of mouthparts vertebrates that consume oligochaetes. Oligochaetes it has. For example, beetles have chewing mouthparts also enhance plant growth by consuming and can eat solid foods such as leaves, stems, and roots and then releasing nutrients into the environment. The of plants. Aphids and bed bugs, on the other hand, have oligochaetes’ tunneling activities also allow more water piercing or sucking mouthparts and can only eat liquids, and to reach plant roots. Many species perform such as plant sap and blood, respectively. Other insects the same services in aquatic systems. By filtering on a strictly liquid diet include butterflies and moths suspended particles from water, bivalves can improve whose mouthparts are a coiled that unwinds water clarity and overall ecosystem health, providing a to siphon nectar from flowers, or moisture from a mud beneficial service to plants, wildlife, and humans. puddle. Finally, house flies have sponging mouthparts that can sop up liquids and the dissolved material liquefied by the enzymes they release onto solid foods. Some of the most well-known carnivorous invertebrates in Iowa are spiders. Spiders are predators that benefit people by eating insects, including those that might be pests. Two closely related species, the wolf and fishing spiders, are some of the largest species of spider found in Iowa. They actively hunt their prey instead of building webs to capture prey as more commonly seen among

Rainbow scarab dung beetle ACTIVITY PATTERNS Body temperatures of invertebrates fluctuate with the environment, so Iowa's cold winters can pose a severe threat to invertebrate survival. Invertebrates have evolved several strategies to adapt to Iowa's wide range of temperatures across the year, generally being most active during warm months (April-October) and changing activities during the cold months. Before it gets really cold in the wintertime, most invertebrates find some shelter or protection from the elements. Invertebrates can slow down their body's function to enter a period of dormancy. Freshwater mussels will burrow more deeply into the sandy beds of the lakes and ponds where they live and shut down Monarch butterfly nectaring on New England aster. feeding when food is scarce. This is known as vertical migration. If food is still available, the mussels can remain actively filter feeding. Insects are better adapted to Iowa's winters than we are. Insects that remain outdoors in Iowa will survive below-freezing temperatures through a process called The Vital Importance of Invertebrates super-cooling. An antifreeze like compound in their body prevents the formation of ice that would be fatal. Some invertebrates can negatively affect human health and well-being by transmitting disease (mosquitoes) or Some invertebrates, like bumble bees, have adaptations contaminating and consuming food supplies. However, for being active even in cooler temperatures. Bumble the vast majority of invertebrates are beneficial to human bees are one of the few groups of invertebrates whose life and the world. Here are just a few of the services species diversity increases as you go north. In Iowa, invertebrates provide: they can be active earlier and later into the year than other invertebrates. They accomplish this by vibrating Helping plants their wing muscles to generate heat. Bumble bee wing • Pollinating vibration also allows them to gather pollen from flowers • Dispersing seeds that hold pollen tightly. • Supplying nutrients • Providing defense The most fantastic adaptation to surviving winters is perhaps the migration exhibited by several insect Helping animals species that leave Iowa to spend the winter in a • Being food for other animals warmer locale. The monarch butterfly is the best- • Giving protection known example. Every year in late summer these large Limiting population growth butterflies fly thousands of miles to a specific area of • Controlling plant populations Mexico where they spend most of the winter perched in • Controlling insect populations clusters in particular groves of fir trees. They make the • Controlling vertebrate populations journey back north in the spring, reproducing along the Cleaning Up way. Certain other butterflies, such as the red admiral, • Recycling dead animals and some dragonflies also migrate south for the winter. • Recycling dung Some insects commonly seen in Iowa during warmer • Recycling dead plants months simply die with the cold weather and then repopulate the state the following year with individuals blown northward during spring storms. The corn earworm and certain leafhoppers survive in warmer climates and ride storm winds into the state each year. On a daily basis invertebrates can exhibit a variety of activity patterns. Some have adapted to a mostly nocturnal lifestyle, like moths and centipedes. Others, like butterflies, need the sun to warm their bodies to the temperatures they need to be active, so are only mobile during the daytime. SUMMING IT UP ACKNOWLEDGEMENTS The abundance and species diversity of invertebrates This article was produced through a collaborative project are declining on a global scale. Causes for these declines led by members of the Iowa Association of Naturalists include conversion of natural ecosystems (prairie, forest) (IAN) and Iowa State University Extension and Outreach. to urban and agricultural landscapes, aquatic habitat Funding for the project was provided by a Resource degradation (nutrient and sediment inputs), and exposure Enhancement and Protection (REAP) Conservation to pesticides and other synthetic chemicals. Education Program grant. There are many ways to help Iowa conserve its diversity of Portions of the text were adapted from or originated in the invertebrates. Replacing just a part of your lawn to native Iowa Insects, Spiders, and Other Invertebrates booklet vegetation, and avoiding the use of chemicals, can have a published by IAN. That booklet, along with others originally positive impact for many invertebrates. Native plants don’t produced as part of a larger series by IAN are digitally need fertilizer or herbicide, and they enrich and aerate the archived at lib.dr.iastate.edu/extension_ian. soil which benefits the micro-organisms and invertebrates that live underground. The plants themselves provide food Authors and shelter to many invertebrates. These plants are better Donald Lewis, Iowa State University than lawn at holding water and preventing damaging runoff Timothy Stewart, Iowa State University from entering waterways. This keeps waters clean for the many invertebrates living there. At a larger scale, the use Stephanie Shepherd, Iowa Department of Natural of buffers along streams around agricultural fields also Resources provides these benefits. Invertebrates are vitally important. This article and others in the Iowa’s Nature series were It's in our best interest to help invertebrate populations reviewed and approved by the Iowa’s Nature Editorial recover, and this can best be accomplished by using Board: Heidi Anderson, Polk County Conservation; Rebekah land in ways that consider their needs. You can make a Beall and Elizabeth Waage, Story County Conservation; difference too, by making lifestyle choices with the welfare Lilly Jensen, Winneshiek County Conservation; Stephanie of invertebrates in mind. Shepherd, Iowa Department of Natural Resources; and Adam Janke and Julia Baker, Iowa State University.

Photo Credits Cover photo of braconid wasp—Larry Reis Soldier fly—Gregory Courtney Zebra mussels on native mussel—Iowa Department of Natural Resources House centipede—Scott Akerman, Wikimedia Twelve-spotted skimmer—Josh Otten Rainbow scarab beetle—Geoff Gallice, Wikimedia Monarch on New England Aster—Bill Ohde

Illustrations Original graphics for this publication were created by Madeline Schill, Iowa State University biological and pre-medical illustration student. All original graphics presented in the article are available to download at high resolution for noncommercial use in educational materials at naturalresources.extension.iastate.edu/Iowas-Nature. In accordance with Federal law and U.S. Department of Agriculture (USDA) civil rights regulations and policies, this institution is prohibited from discriminating on the basis of race, color, national origin, , age, disability, and reprisal or retaliation for prior civil rights activity. (Not all prohibited bases apply to all programs.) Program information may be made available in languages other than English. Persons with disabilities who require alternative means of communication for program information (e.g., Braille, large print, audiotape, and American Sign Language) should contact the responsible State or local Agency that administers the program or USDA’s TARGET Center at 202-720-2600 (voice and TTY) or contact USDA through the Federal Relay Service at 800-877-8339. To file a program discrimination complaint, a complainant should complete a Form AD-3027, USDA Program Discrimination Complaint Form, which can be obtained online at https://www.ocio. usda.gov/document/ad-3027, from any USDA office, by calling 866-632- 9992, or by writing a letter addressed to USDA. The letter must contain the complainant’s name, address, telephone number, and a written description of the alleged discriminatory action in sufficient detail to inform the Assistant Secretary for Civil Rights (ASCR) about the nature and date of an alleged civil rights violation. The completed AD-3027 form or letter must be submitted to USDA by: (1) Mail: U.S. Department of Agriculture Office of the Assistant Secretary for Civil Rights, 1400 Independence Avenue, SW Washington, D.C. 20250-9410; or (2) Fax: 833-256-1665 or 202-690-7442; or (3) Email: program.intake@usda. gov. This institution is an equal opportunity provider. For the full non- discrimination statement or accommodation inquiries, go to www.extension.iastate.edu/diversity/ext.

WL17f March 2021