iowa wildlife series - iowa insects, spiders, and other ... · butterflies are toxic to some...

Iowa Association of Naturalists

Iowa Insects, Spiders,and Other Invertebrates

Iowa Wildlife Series

Iowa Wildlife SeriesStudents need to be knowledgeable about and appreciate local wildlife in order to better understand thenatural environment. The Iowa Association of Naturalists has created this series of booklets to offer abasic understandable overview of Iowa wildlife. These booklets will assist educators in teaching studentsabout Iowa wildlife. The six booklets in this series are:

Iowa Mammals (IAN-601)Iowa Winter Birds (IAN-602)Iowa Nesting Birds (IAN-603)Iowa Reptiles and Amphibians (IAN-604)Iowa Fish (IAN-605)Iowa Insects and Other Invertebrates (IAN-606)

Editorial BoardText: Detra Dettmann-EaslerIllustrations: Mark MüllerDesign and Layout: Dan Cohen, Writing and Publications ServicesPublished by: Iowa Association of Naturalists

The Iowa Wildlife Series is publishedby the Iowa Association of Naturalistswith major funding from the REAPConservation Education Board and theIowa Conservation Education Council(September 1998).

Review CommitteeCele Burnett, Consultant, E Resources Group, Inc.Dan Cohen, Naturalist, Buchanan County Conservation BoardDetra Dettmann-Easler, Camp and Program Director, Louisa County Conservation BoardJean Eells, Consultant, E Resources Group, Inc.Judy Levings, State 4-H Youth Development Specialist, Iowa State UniversityJim Pease, Extension Wildlife Specialist, Iowa State UniversityDiane Pixler, Naturalist, Marshall County Conservation BoardA. Jay Winter, Training Officer, Iowa Department of Natural Resources

The Iowa Association of Naturalists (IAN) is a nonprofit organization ofpeople interested in promoting the development of skills and educationwithin the art of interpreting the natural and cultural environment. IANwas founded in 1978 and may be contacted by writing the ConservationEducation Center, 2473 160th Rd., Guthrie Center, IA 50115, 515/747-8383.



Iowa Insects, Spiders, and Other Invertebrates

1

Iowa Insects, Spiders, andOther Invertebrates

What is an invertebrate?

The six-leggeds: insects

nvertebrates are small animalswithout backbones. Manyinvertebrates have bodies divided into

distinct regions and an external skeleton.Other invertebrates do not have these features.Most animals on this planet are invertebrates.

Classifying invertebrates can sometimes beconfusing. People sometimes call centipedes andsowbugs “insects,” when in fact theyare not. Invertebrates havespecific characteristicswhich determine exactlywhat kind of animal they are.

hey hop, creep, fly, and swim. They live inforests, prairies, ponds, and rivers. Theylive in tops of trees and under the ground.

We even find them in our homes. Some areconsidered pests and others objects of beauty.They are the most diverse and prosperous of allanimals. They are insects.

I

T



2

What is an insect?

Insects have six legs and three body parts calledthe head, thorax, and abdomen. They also havean external skeleton. The eyes, antennae, andmouthparts are located on the head. Most insectshave compound eyes, which are one eye made upof many smaller eyes, as well as simple eyes. Thesimple eyes look like a small dot in front of thelarger compound eyes. The mouthparts of insectsare generally of two types - chewing and sucking.Chewing insects have mandibles which move backand forth to chew up food. Sucking insects havemouthparts modified into a beak with which theysuck liquid.

The legs and wings of insects are attached to thethorax. Insects may have no wings, one pair, ortwo pairs of wings. Other appendages such ascerci (pronounced sir-see) and reproductive organsare sometimes visible at the end of the abdomen.

Incredible insects

Insects are the most numerous group of animals onEarth. There are more than 750,000 differentkinds of insects known. This is more than all theother animal groups combined! Springtails in thesoil can number more than 900 million per acre,and a single female aphid can have 500 billiondescendants in a single year. This may seemoverwhelming. Fortunately, 95 percent of allinsects are either harmless or actually helpful tohumans.

On Earth, there are many areas devoid of humanlife, but few are without insect life. Insects haveexisted on Earth for more than 200 million years,living in all conditions ranging from boiling hotsprings to icy Antarctica.

Abdomen Thorax Head



3

Insects have incredible adaptationsfor survival. Ants, bees, andtermites live in colonies withhierarchies and divisions oflabor. Viceroy butterfly larvaeare camouflaged to look likebird droppings. Monarchbutterflies are toxic to somepredators. Some insects suchas flies, moths, and beetleshave complete metamorphosis involving fourstages: egg, larva, pupa, and adult. Most insects,such as grasshoppers, have incomplete or simplemetamorphosis in which an immature nymphhatches, grows, develops wings, and continues togrow into adult size. Some insects hatch youngthat look like miniature adults. All theseadaptations have made insects some of the mostabundant creatures on Earth - underground, onthe ground, in the skies, and underwater.

Crawlers on the ground — Beetles

One of the most common insect orders foundcrawling on the ground is beetles. Beetles are themost diverse insect group and have the largestnumber of species of any group of organisms. Oneout of four insects identified so far is a beetle. If a

“The creator, if he exists, has an inordinate fondness for beetles on observingthat there are 300,000 species of beetles on this planet, but only 8,000 speciesof mammals.”

JBS Haldane, Scottish mathematical biologist (1892-1964)

Egg

Pupa

Larva

Adult

Complete metamorphosis

Incompletemetamorphosis



4

person began collecting beetles at the rate of onenew species every day, their life wouldn’t be longenough to collect them all. There are more than300,000 known kinds of beetles!

The most distinguishing characteristic of beetlesmay be the hard front wings which protect thesofter rear wings and abdomen. They also havepowerful jaws for chewing. Beetles are adapted tolive in a variety of habitats. Some live under barkand some bore into stems, wood, seeds, and roots.Some are predators living in leaf litter, leaf mold,soil, or gravel. Others feed on carrion, leaves,decaying vegetation, or fungi.

Name Description Other informationStag beetle Males have huge mandibles Adults feed on sap; larvae feed on

which resemble antlers on juice from decaying woodmale deer (stags)

Nine-spotted Orange to reddish-yellow Helpful predators; adults andladybird beetle front wings with four black larvae feed on aphids and are(ladybug) spots on each wing and a spot beneficial to some crops

where the two wings cometogether

Dermestid beetle Covered with hair; appear Feed on many things, includingblack or brownish; cereal, woolen rugs, woolensometimes with a pattern upholstery, mounted bird or

mammal specimens; leaves a pileof powdery material as evidence ofits presence

Acorn weevil Has a long, slender snout Adults drill holes in acorns andwhich is as long as the body drop in an egg; look for acornsor longer with holes in early fall

Examples of beetles in Iowa

Stag beetle



5

Beetle-like insects

Earwigs are another crawling insect.Earwigs were named because they werebelieved to crawl into the ears ofsleeping people but this is almost un-heard of. Earwigs have short, flexiblefront wings and they have pincer-likecerci (sir-see) attached to their abdo-men. These cerci are for defense andcan sometimes cause a painful pinch. Femaleshave straight cerci compared to the males’ curvedcerci. They are nocturnal and spend the day increvices or damp places.

Cockroaches usually do not win popularity contestswith people, but they have an ancient andimpressive lineage. Back in the days when coalswamps covered a good portion of America,cockroaches were often six inches long. In the 300million years that have passed, present-daycockroaches have never matched their ancestor’ssize but have found many habitats to their liking.

Cockroaches have flat, oval bodies and aregenerally black or brown. They usually have wingsbut their front wings are more leathery. Somecockroach species are at home under logs andstones. Most are nocturnal and, with their flat-tened shape, are able to invade homes and publicbuildings. They eat mostly organic material andcan be hard to control. They have two cerci at theirposterior end which detect sounds and aresensitive to puffs of air which may come from yourfoot or hand. This adaptation, along with beingrapid runners, makes them especially difficult toswat or step on.

Earwig



6

Aphids and aphid-like insects

Just as we tap maple trees for their sugar-rich sap,many insects tap stems and leaves for the samereason. Aphids are small, pear-shaped insectswith sucking mouthparts. By sucking plant juices,aphids can cause plants to wilt. They can alsotransmit diseases as they feed. Ladybugs helpcombat this problem by eating aphids.

Aphids sometimes live closely withants. Aphids use only a portion of thesugars found in the plant juice and

discharge the rest as a clearwatery liquid, called honeydew,from their anus. This honeydewmay attract ants and other

insects. Ants will eat this honeydew, and someants gather aphid eggs and keep them over winterin their nest. In spring, they transport the aphidsto a food plant and tend to them by transferringthem from one plant to another.

Aphids - This is your life!

Each year, aphids hatch from eggs laid the preceding fall. All theseaphids are wingless females. These females do not mate and do not

lay eggs but give birth to live young through parthenogenesis - producingyoung from unfertilized eggs. These young are just like their mothers- wingless females. The cycle continues with a new generation of winglessfemales appearing as often as every ten days. This lasts until the leavesand stems where they feed become too crowded. Then the winglessmothers give birth to winged daughters that fly off to colonize new leavesand stems. These winged generations can alternate with the winglessgenerations several times during the course of the summer until the finalgeneration - twelfth or thirteenth - appears. Only at this point do maleaphids finally hatch and mate with females. This brings the year to anend, as it began, with the fertilized eggs left behind.

Ant eating aphid honeydew



7

Another sap-feeding insect is theboxelder bug. Boxelder bugs are in agroup called plant bugs. They areblackish with red markings and feedon sap from boxelder trees. They oftenenter our homes in the fall.

Ants and termites

Ants and termites are crawling insects have com-plex social structures. There are more than 2,500species of ants and all are social animals. Antcolonies can be found in large numbers everywherebeneath our feet. Ants are black, brown, or red incolor and may have wings or be wingless. Theyhave a thin waist between the thorax andabdomen.

The ants of a particular colony usually only haveone queen which is the mother of all the workers.These workers are all females. While the queencontinues laying more and more eggs, workers tendthe eggs, feed and clean their younger sisters, andsearch for food above ground.

Periodically, this routine is broken whenwinged ants develop from the eggs laid by theold queen. These are males and new queenswhich swarm from the colony to mate. Cloudsof flying and mating ants are sometimescommon in the spring. The smaller males soon dieafter this aerial adventure. The larger queens biteoff their own wings and settle down to start newcolonies beneath the ground.

Termites are sometimes called white ants but theyare not ants. They have a thick body from head totail, lacking the thin waist characteristic of ants.They are small, pale in color, and live in dampwood. They are also highly socialized and live incolonies with four distinct castes, or social classes.

Not all insects are ”bugs.“ Truebugs have sucking mouthparts,and many suck sap from plants.In North America, about 3,800species, including the boxelderbug shown above, are true bugs.

Carpenter ant



8

The first caste is made up of the king, the queen,and the winged termites which may become kingsand queens of new colonies. The second caste ismade up of whitish, blind workers hatched fromthe thousands of eggs laid by the enlarged andalmost helpless queen. The last two castes aremade up of soldiers, with large heads and jawsthat protect the nest from enemies, and nymphswhich take over the task of reproduction shouldthe king or queen die.

Termites have protozoa in their digestive tractswhich allow them to feed upon and digest wood.Each year termites do approximately one billiondollars worth of damage to buildings in the UnitedStates.

The hoppers

Hopping insects offer fun and challenge whentrying to catch them. Their rear set of legs aremodified for jumping. The best known members ofthis group are the grasshoppers, katydids, andcrickets. Each has a long abdomen, a large,flat-sided head, and chewing mouthparts. In yearswhen these species are prolific, they can doconsiderable defoliation and crop damage.Periodically, they swarm. These insects serve asfood for larger birds, small mammals, and otheranimals. Some katydids and crickets make music

by rubbing a file on the undersurface of onewing against a rough patch on the

upper surface of the otherwing. Some malegrasshoppers rub theirlegs against their wingsor snap their wings inflight. These “concerts”only are performed in latesummer when they havereached full maturity.

More than 2,000 kinds of cricketshas been identified. Each has itsown distinctive song.



9

Examples of hoppers in Iowa

Common Name Description Other informationNebraska conehead Long-horned grasshopper; Found in tall grass or other tall

long, slender antennae; grass-like plants; high-pitchedgreen in color buzzy song

Bush katydid Long-horned grasshopper; Hear with “ears” on upper part ofgreen with thin, leaf-like the front legswing covers

Field cricket Black or brown in color; Their song is probably the mostcommon familiar to people

Leafhoppers and treehoppers are hopping insectswith sucking mouthparts that produce honeydewsimilar to aphids. Leafhoppers are often green incolor but can also have bright spots or stripes.Treehoppers have incredible jumping ability andare known for some of their bizarre shapes andcolors which keep them camouflaged among plants.Often, this camouflage is so effective they only arenoticed while moving. For example, the buffalotreehopper is camouflaged like a green thorn.

Froghoppers are small jumping insects which aredull in color and shaped somewhat like tiny frogs.The nymphs, known as spittlebugs, are recognizedby the whitish froth they produce to coverthemselves while feeding. They are commonlyfound in grass and weeds. If you separate the frothon the plant and peek in, it islikely you will see the small,green nymph inside.

Bush katydid

Spittlebug



10

Fleas are generally an unpopular hopping insect,although they do carry the prestige of being theinsect high-jump champions. They can jump up to150 times their body length, sideways or straightup. This would be equivalent to a human jumpingabout 1,000 feet! Fleas often are observed bypeople merely as a brown speck running across thehair of a pet. A closer look, however, revealsinteresting adaptations to keep them close to theirhost. Their bodies are vertically flattened withantennae in grooves behind the eyes where theycannot snag hair. They also have hooked claws tohelp them keep their grasp in a tangle of hairs.Fleas are difficult to catch which can befrustrating since they are considered pests tohumans and pets. Adult fleas feed on blood fromtheir hosts. Larvae feed on dust and debris.

High in the sky

Insects in the sky have many interesting behaviorsand adaptations for their aerial way of life. Someflying insects make people nervous as they buzzby, while others offer great beauty and pleasurebeing sighted. A whole book could easily bededicated just to flying insects. A few of the morecommon groups will be discussed here.

Flies

The fact that most homes are equipped with aflyswatter indicates that flies are considered acommon nuisance. Because we encounter them sooften, they are insects that are familiar to us.Flies have just one pair of wings, as opposed toother common flying insects which have two pairs.Where other insects have a second pair of wings,flies have knobs attached to the thorax. If theseknobs are injured, they cannot fly.



11

Bees and wasps

Bees and wasps are fliers whichsend some people into a panic.Many types of flies are mistaken forbees but a close look, if you dare,will let you know if you need tomake a “beeline” or not. Bees andwasps have four clear-coloredwings, as opposed to just two foundon flies. This group also hasslender waists and mouthparts forchewing and sucking. They are the only insectswith stingers. Their yellow and black stripesadvertise these stingers to other animals who maywant to eat them. Usually people are not stungunless they disturb a nest.

Many bees live in large nests with a queen thatlays the eggs and is cared for by the femaleworkers. Not all bees live in hives. Bumblebeesare mostly solitary and make their homes in holesin the ground or sometimes use an old mouse nest.

Butterflies, moths, and skippers

Butterflies, moths, and skippers may be the mostattractive group of insects for many people. Thesefliers have two pairs of wings. The body and wingsare covered with scales to give them their color.The mouthparts are modified into a sucking tubefor feeding on nectar or sap. These insects havecomplete metamorphosis, including egg, larva,pupa, and adult.

There is no rule of thumb to distinguish thecaterpillars of moths from those of butterflies.Both have chewing mouthparts and can do damageto some crops. Adult moths and butterflies arequite different, although one group, the skippers,show characteristics of both groups. Butterflies

Honeybee

Hover fly



12

usually are active during the day, while moths flyat night. Butterflies rest with their wings folded,while moths rest with theirs spread apart.Butterflies have antennae which are thin, endingin a knob, while antennae of moths never end inknobs and are often feathery. Though butterfliesoften are considered more attractive, the mothsform a larger, more diverse group.

Skippers are small butterflies with characteristicsof moths. They have a rapid, darting flight. Thefront and hind wings at rest are usually held atslightly different angles from each other.

Dragonflies and damselflies

Dragonflies and damselflies live near water. Theyhave large, slender bodies and large compoundeyes, and are predaceous. Both have two rows oflong, sharp spines on their legs which they use tosnag mosquitoes, gnats, and midges in flight.

Dragonflies are one of the fastest insects, usingtheir powerful wings to propel them atspeeds ranging from 35 to 60 mph. Theycome to rest quietly with their wingsoutstretched. Dragonflies also have theability to hover in one place and fly back-

wards. Green darners are common dragonflieswith a green thorax, bluish abdomen, and target-like mark on the upper part of the head.

Damselflies are named for damsels - elegantwomen of noble birth. The damselfly’s flight ismore fluttering and weaker than the dragonfly.Damselflies hold their wings resting elegantlyerect over their back, like a butterfly. Onecommon damselfly in Iowa is the black-wingeddamselfly. Males have blackish wings and ametallic-greenish-black body. Females have darkgray wings with a white spot on the front edge ofthe wing and a non-iridescent colored body.

Dragonflies may have morethan 28,000 tiny lenses intheir eyes giving them thesharpest vision of any insect.



13

Lacewings

Lacewings are characterized by their four thinwings with a network of visible veins. These wingsoften are held roof-like when the insect is at rest.Most are poor-flying predators seen flying at nightaround lights. Silver-spotted

Skipper

Examples of flying insects in Iowa

Common name Description Other informationDeer fly About the size of a house fly; Females give a painful bite

light tan markings and while attempting to suck bloodmarkings on wings

Mosquito Small size; males have Only females bite to get blood forfeathery antennae; females their eggs to develophave a few hairs on antennae

Honeybee Have pollen baskets of stiff A midsummer hive has one queen,hairs on legs to carry pollen approximately 50,000 sterile femaleback to the hive; workers workers, and a few hundred maleonly sting once, leaving the dronesstinger in the victim’s bodyand then dying

Paper wasp Brownish with long legs; Queen builds a paper nest out ofpainful sting wood it rasps from a tree and mixes

with saliva; nests are open and lacka covering like a hornet’s nest

Yellow jacket (hornet) Black and yellow bands on Queen builds a paper nest aboutabdomen; painful sting one-inch in diameter; as workers

are produced, nest may be expandedto a foot in diameter

Monarch butterfly Black and orange; males In fall, swarms of adults migratehave black spot on third southward, covering entire treesvein of back wing; while resting; larvae feed solely onWingspan: 95-105 mm. milkweed

Luna moth Delicate, light green color; Larvae feed on sweet gum, walnut,distinctive tail; hickory, and persimmon treesWingspan: 100-120 mm.

Silver-spotted skipper Black wings with orange Larvae feed on leaves and live in astripes on upper wings; white shelter of rolled-up leavesblotches on lower wings;Wingspan: 44-60 mm.

Green lacewing Green wings and golden eyes Sometimes called aphid lions;important in keeping pest aphidsunder control

Dobsonfly Large, soft body; found near Larvae are called hellgrammites;streams; males have huge often used as live fishing baitcurved mandibles for claspingfemales during mating



14

Diving deep

Many people who have had the opportunity to dipa net into an Iowa pond have been amazed at whatthey found. There are approximately 5,000 speciesof insects which spend all or part of their lives inNorth American ponds and lakes. These insectshave fascinating adaptations for breathing,capturing food, rearing young, and escapingpredators in their watery world. An abundance ofimmature and adult insects play important rolesin aquatic food webs. Many of these small crittersare vital to the growth and success of fishpopulations and fishing opportunities.

Aquatic larvae and nymphs

Mosquito larvae are approximately one-quarterinch long. Their head and thorax are much largerthan the rest of their body. They breathe at thesurface of the water through the help of a siphonon their posterior end. They eat microscopicplants and animals or organic debris filteredthrough brushes that surround their mouth. Theytake just a week to develop into an adult.

Dragonfly and damselfly nymphs are not likelyto win any beauty contests. The nymphs aredull-colored, awkward-looking creatures. Theycatch their prey using an enlarged lower lip calleda mask, armed with a pair of hooks which can beshot out of the head to hook prey and then drawnback into the jaws. Nymphs prey on tadpoles,small fish, and other aquatic insects. Damselflynymphs are slim and have three leaf-shaped gillsat the tip of the abdomen. Dragonfly nymphs are

more broad and lackthese gills. Bothof these nymphsserve as food forlarge fish.

Dragonfly and damselfly nymphssnatch their prey with a pair ofhooks that can be shot out andretracted back into the head.



15

Stonefly nymphs generally live in flowing waterwhere they are found under rocks, leaves, andother debris. They grow up to two inches long andhave tufts of gills behind each leg. Some feed onplants, while others feed on animals. Fish andother water animals feed on stonefly nymphs.

Mayfly nymphs have rows of leaf-like gills alongthe sides of their abdomen and, like the adults,have three long tail appendages. They live from afew months to a few years in the water, dependingon the species. As they near maturity, they float tothe surface, shed their skin, and transform to asub-adult and then to an adult. As adults, they donot have functional mouthparts and cannot feed.They merely mate in flight. The female lays hereggs in the water and the adults die. Both thenymphs and adults are important food for fish.

Caddisfly larvae are home builders of the waterworld. They are found in Iowa streams and live ina case of leaves, sand, grains, twigs, or other debrisglued together by sticky silk. They spend all theirtime as larvae in these cases and are anchored inthem by two tail hooks. As the larvae grow andmolt, they simply remodel and expand their casesby adding material to the entrances. Caddisflyspecies can be identified by examining the forms oftheir cases.

Aquatic adult insects

Whirligig beetles are black, round beetles foundwhirling like a top on the surface of the water.They use their short, fan-shaped middle and hindlegs for skimming and diving. These beetles don’tneed liability insurance because they never runinto one another. Their antennae float on thesurface and monitor all ripples that come theirway. This “radar” allows them to makesplit-second changes in their direction of travel.

EncasedcaddisflyLarvae

Caddisflywithout a case



16

Perhaps most unique about this beetle is that ithas its own version of bifocals - each eye is dividedinto two parts so the beetle can see above andbelow the water at the same time.

Two insects use their hind legs as oars in thewater. The first is the backswimmer,appropriately named since it swims on its back. Itis able to do this by carrying air supplies on itsbelly and beneath its wings. They come to restand replenish their air supplies by sticking the tipof their abdomen above the water surface. Be

careful when picking up a backswimmer- their bite can be painful.

The other insect with “oars” is the waterboatman which swims on its belly. As

the water boatman rows through thewater, its entire body glistens from the blanket

of air that wraps around it. Thousands of tinyhairs coat the surface of the boatman’s body andhold the blanket of air in place. In order for theinsect to stay underwater, it must hold onto someobject. Adult water boatmen feed on algae ordecaying plant and animal matter sucked from thebottom mud.

Another insect gracing Iowa waters is the divingbeetle, unsurpassed among aquatic insects forgrace and speed. Both the adults and larvae arepredaceous and will eat any insect, snail, fish, ortadpole they are fast enough and strong enough tocatch. Adults have spiracles which open betweentheir abdomens and wing cases. Spiracles aresmall holes along the abdomen through whichinsects breathe. Each time a diving beetlesurfaces, it sticks the end of its abdomen out of thewater and collects air beneath its wing case for thenext dive. Out of the water, adults are strongfliers and often are attracted to lights.

Backswimmer



17

Wolf spider

The eight-leggeds: spiders, ticks, and mites

Spiders, ticks, and mites belong to agroup called arachnids, a Greekword for spider. They have two body

parts: a cephalothorax, which is a combinedhead and thorax, and an abdomen. They haveeight legs, no antennae, and no wings. Likeinsects, they have an external skeleton.

Spiders

Spider have all the basic arachnid characteristicsand usually eight simple eyes - never compoundlike insects. They do not chew and swallow theirprey. They crushes their prey with nippers calledchelicerae attached to their heads. There are twoways spiders ingest their food. Those with weakjaws puncture the body of their prey with theirchelicerae and alternate between injecting andsucking back digestive fluids which dissolve thesoft parts until all that remains is the empty shell.Spiders with strong jaws such as wolf spiders andlarge orb weavers mash their prey to pulp betweentheir jaws as the digestive fluid is regurgitatedover it. Only a small mass of indigestible materialremains to be discarded.

Most spiders are not dangerous to people, but thereare a few exceptions. The most well-knownvenomous species is the black widow. It has abright red mark on its abdomen. Fortunately, it isnot commonly found in Iowa. Another venomousspider is the brown recluse or violin spider. It isyellowish- brown with a dark mark resembling aviolin on the cephalothorax. It is more commonthan the black widow, but is still not numerous.



18

Spiders produce silk. A few adult insects andsome larvae such as caterpillars produce silk, buttheir silk glands are in the head and emerge fromthe lower lip. Spiders have their silk glands in the

abdomen and thestrands come out ofopenings on spinningfingers at the hind end.The silk changes froma liquid to a solid as ithits the air.

Threads of versatility

Spiders use silk for traplines, draglines, ballooninglines, egg sacs and nursery webs, chambers inwhich to hibernate or mate, webs designed tosnare food, and traps to entangle and swathe theirprey. These strands are very strong and can bestretched as much as one-half their normal lengthbefore breaking. Some strands are stronger thanothers. The strength depends somewhat on thespeed at which the fibers are drawn out of thebody - the greater the speed, the greater thestrength. Many of the threads are made up ofmore than one strand.

People are often most fascinated by a spider’suse of silk for their webs. Webs vary from

irregular cobwebs tucked into a corner of thehouse to beautiful orbs found in the garden.

Each type of web is built with a preciseplan. For example, the orb spider begins

with a suspension bridge, upon whichthe whole web will hang. After this isestablished, the spider joins two orthree more lines to make the triangle orrectangle outline. Next the lines arelaid in which the round trap is formed.The spider attaches the lines thatresemble spokes of a wheel using dry

Soon after hatching, manyspiderlings let out lines ofsilk that catch the windand lift them into the air tosettle down to a new home.Spiderlings have been foundballooning 14,000 feet above Earthand 200 miles from shore.

The commongarden spiderspins an orb web



19

silk so it can walk on these lines like scaffolding.The spider finishes the job using sticky threads tofill in the corners and spiral around the spokes tomake the sticky snare. It cuts away the temporaryscaffolding as it leaves the gummy trap behind.People have wondered how spiders keep fromgetting caught in their own webs. The secret is oilfound on the spider’s body.

Daddy longlegs are also arachnids but not truespiders. They are in their own group. Daddylonglegs are recognized by their long, thin legs andone-part body. They do not spin silk. They areoften seen in great numbers in the fall aroundharvest and sometimes are called harvestmen.These critters are harmless to people. They arescavengers and feed mostly on dead animals.Sometimes they may kill small insects and suckjuice from soft vegetables and other foods.

Ticks

Ticks have a one-part body and are externalparasites, meaning they attach to the outside of aliving host to get their nutrients - blood. Tickscarry and transmit a number of disease-carryingorganisms which can infect humans. These includethe organisms which cause Lyme disease, RockyMountain spotted fever, and tick-borne relapsingfever.

Many people believe ticks fall out of trees when, infact, ticks most often live in tall grass. They seekout hosts by questing—grasping the blades ofgrass with their lower legs and waving their frontlegs, waiting for a suitable host to come walkingby. Once a host brushes by their waiting legs,they climb aboard and seek a suitable site forattaching. The tick inserts its mandibles into theskin and begins to suck blood. The outside surface

Daddy longlegs



20

of a tick is made of cuticle and is able to growto accommodate the large volume of ingestedblood, which for some ticks can be 200-600times their unfed body weight!

Mites

Mites have the same physical characteristics asticks but are more predatory. Mites are the mostabundant eight-legged creatures on the planet butoften are overlooked due to their small size. Onestudy gave an estimate of 666 million mites in oneacre of grassland! Mites can be found in thenostrils of seals, the gills of crayfish, and thehearing organs of moths. In Iowa, many mites arefound in the leaf litter.

Tick questing

Lone star tick

Examples of arachnids in Iowa

Common name Description Other informationWolf spider Dark brown with gray hairs; Air tubes which supply air to the

may be more than an inch eyes also act as light reflectorslong

American dog tick Larger size (3/16 inches); Most common tick in Iowa; does notwhite pattern on dorsal transmit Lyme diseaseshield contrasting withdark-brown body

Lone star tick Same size as American dog Has been known to transmit Lymetick; white star on base of diseasedorsal shield; chestnut-browncolor

Black-legged Less than 1/16 inches long; Relatively uncommon in Iowa;(Deer) tick blackish dorsal shield and biggest tick transmitter of Lyme

reddish brown body disease

Red velvet mite Large (by mite standards); Feeds on eggs of other small animalsbright red in color in leaf litter

Dog tick



21

The many-leggeds

Sowbug

Centipede

Centipedes and millipedes often areconfused with insects each are in separatetaxonomic classes. They both have many

body segments, many legs, and an externalskeleton.

Centipedes have long antennae and just one pairof legs on each segment. Millipedes have shortantennae and two pairs of legs on each segment.Centipedes are generally faster than millipedes,but both can have more than 100 pairs of legs.Both use chemical repellents to ward off insectsand other predators. If you disturb a millipede orcentipede, it’s likely you will come away with afoul-smelling odor on your fingers.

Crustaceans

Crustaceans have two body parts - a cephalothoraxand abdomen. The cephalothorax often has ahardened cover called a carapace. They usuallyhave at least five pairs of legs and two pairs ofantennae.

Crayfish are Iowa’s version of lobsters. They havea carapace and five pairs of walking legs. The firstpair of legs are enlarged pincers used for holdingand tearing food. They eat mainly plants andscavenge on dead plants and animals. They areactive mostly at night.

Isopods are small land-dwelling crustaceans.They have flattened bodies and lack carapaces.Pillbugs and sowbugs are examples of isopods.They both have many legs and are often foundunder rotting logs. Pill bugs have the ability to roll



22

into a ball when touched. Their genus name isArmadillidium, because armadillos use the sameprotective tactic. Female isopods carry their eggsand newly hatched young in pouches on the lowersurface of their body - much like kangaroos andopossums!

Leeches and earthworms are both annelids.Annelids are segmented animals with littledifference between body regions. They do

not have an external skeleton, and the annelidsdiscussed here do not have legs.

Leeches are sometimes called bloodsuckersalthough not all feed on blood. Leeches areflattened worms often found in calm, warm,shallow waters with bottom debris. They movearound by swimming and by looping - alternatelyattaching the mouth sucker and tail sucker to thebottom surface. Blood-sucking leeches havewell-developed jaws, while scavenger andcarnivorous species do not.

Earthworms are annelids with four pairs of setae- retractable bristles on each body segment. Theyfeed on detritus. They dig extensive tunnelsystems by swallowing soil as they burrow makinguse of any food present in the particles. The soilthat remains is excreted into castings which aresmall mounds commonly seen along the groundsurface. In a single acre, there can be more than amillion earthworms, eating ten tons of leaves,stems, and dead roots per year and turning over 40tons of soil! This activity makes earthwormsefficient underground farmers, turning and aerat-ing the soil like a fine plow. This aerated soil andfertilization enhance plant growth.

The zero-leggeds: leeches and earthworms

Earthworm casting



23

Earthworms have another interesting adaptation.They are hermaphrodites. Each individualpossesses both male and female reproductive parts.Earthworms mate by lying on the surface of theground while each individual lays eggs in a cocoon.

Since most insects and many invertebratesare small, it is easy to underestimatetheir role in the ecosystem. However, many

of these creatures are important food sources forlarger species of insects, birds, fish, reptiles,amphibians, and mammals. Insects are alsoimportant plant pollinators. Still others, such asearthworms, play significant roles in improvingsoil quality - a vital part of Iowa’s farmingeconomy.

There are manyreasons to learnmore aboutIowa’s insects andinvertebrates. Notonly do they playimportant roles inthe ecosystem andgreatly impact ourlives, but they alsohave many specialadaptations forsurvival. See theUseful Resourcessection of thisbooklet to learnmore about thesefascinating creatures.

Good things in small packages



24

Bug Watcher: Iowa Youth and 4-H Entomology (4-H 423A); Iowa State University Extension; ISUExtension Publications Service, Ames, IA; 1997.

Close Encounters with Insects and Spiders; James B. Nardi; Iowa State University Press, Ames,Iowa; 1988.

Encyclopedia of Insects and Arachnids; Maurice and Robert Burton; Octopus Books; 1975.Entomology at Iowa State University; http://www.ent.iastate.edu/

Information about insects and ticks in Iowa.A Field Guide to the Insects; Donald J. Borror and Richard E. White; Houghton Mifflin Company,

Boston, MA; 1970.The Golden Book of Insects and Spiders; Laurence Pringle; Western Publishing Company, Inc.,

Racine, WI; 1990.A Guide to Spiders and Their Kin; Herbert W. Levi and Lorna R. Levi; Western Publishing

Company, Inc., Racine, WI; 1968.The How and Why Wonder Book of Insects; Ronald N. Rood; Wonder Books, Inc., New York, NY;

1960.IAN Booklet Series; Iowa Association of Naturalists; ISU Extension Service, Ames, Iowa.

Adapting to Iowa (IAN-408); Iowa Wildlife and People Series; 1996.Iowa’s Biological Communities (IAN-201); Iowa’s Biological Communities;1994.Iowa Food Webs and other Interrelationships (IAN-405); Iowa Wildlife and People Series;

1996.Iowa Prairies (IAN-203); Iowa’s Biological Communities; 1994.Iowa Waterways (IAN-205); Iowa’s Biological Communities; 1994.Iowa Wetlands (IAN-204); Iowa’s Biological Communities; 1994.Iowa Woodlands (IAN-202); Iowa’s Biological Communities; 1994.Misconceptions about Iowa Wildlife (IAN-403); Iowa Wildlife and People Series; 1996.

Insect Biology: A Textbook of Entomology; Howard E. Evans; Addison-Wesley Publishing Company,Inc., Reading, MA; 1984.

Insects; Steve Parker; Dorling Kindersley, Inc., New York, NY; 1992.Insects: A Guide to Familiar American Insects; Herbert S. Zim and Clarence Cottam; Western

Publishing Company, Inc., Racine, WI; 1987.Pond Life: A Guide to Common Plants and Animals of North American Ponds and Lakes;

George K. Reid; Western Publishing Company, Inc., Racine, WI; 1987.Simon and Schuster’s Guide to Insects; Ross H. Arnett, Jr. and Richard L. Jacques, Jr.; Simon and

Schuster, New York, NY; 1981.The Story of Spiders; Dorothy E. Shuttlesworth; Garden City Books, Garden City, NY; 1959.The Strange Lives of Familiar Insects; Edwin Way Teale; Dodd, Mead & Company, New York, NY;

1962.

Useful resources

Iowa Insects and Other Invertebrates is one in a series of six booklets that are part of the IowaWildlife Series. The booklets in the series include:

Iowa Wildlife SeriesIowa Mammals (IAN-601)Iowa Winter Birds (IAN-602)Iowa Nesting Birds (IAN-603)Iowa Reptiles and Amphibians (IAN-604)Iowa Fish (IAN-605)Iowa Insects and Other Invertebrates (IAN-606)

The Iowa Association of Naturalists also has produced five other booklet series that provide readerswith a clear, understandable overview of topics concerning the Iowa environment and conservation. Thebooklets included in each of the other five series are listed below.

Iowa’s Natural Resource HeritageChanging Land Use and Values (IAN 501)Famous Iowa Conservationists (IAN 502)Iowa’s Environmental Laws (IAN 503)

Iowa Wildlife and PeopleIowa Wildlife Management (IAN-401)Keeping Iowa Wildlife Wild (IAN-402)Misconceptions About Iowa Wildlife (IAN-403)State Symbols of Iowa (IAN-404)Iowa Food Webs and Other Interrelationships (IAN-405)Natural Cycles In Iowa (IAN-406)Iowa Biodiversity (IAN-407)Adapting To Iowa (IAN-408)

Iowa PlantsIowa’s Spring Wildflowers (IAN-301)Iowa’s Summer and Fall Wildflowers (IAN-302)Benefits and Dangers of Iowa Plants (IAN-303)Iowa’s Trees (IAN-304)Seeds, Nuts, and Fruits of Iowa Plants (IAN-305)Iowa’s Mushrooms and Other Nonflowering Plants (IAN-306)Iowa’s Shrubs and Vines (IAN-307)

Iowa’s Biological CommunitiesIowa’s Biological Communities (IAN-201)Iowa Woodlands (IAN-202)Iowa Prairies (IAN-203)Iowa Wetlands (IAN-204)Iowa Waterways (IAN-205)

Iowa Environmental IssuesIowa Habitat Loss and Disappearing Wildlife (IAN-101)Iowa Air Pollution (IAN-102)Iowa Water Pollution (IAN-103)Iowa Agricultural Practices and the Environment (IAN-104)People, Communities, and Their Iowa Environment (IAN-105)Energy In Iowa (IAN-106)Iowa Waste Management (IAN-107)

√ Booklets may be orderedthrough the Iowa State

University Extension Service ata cost of $1.00 per booklet.When ordering, be sure to usethe IAN number to the right ofeach listed booklet title.Please send written orders andpayment to:

ISU Extension ServicePrinting and Publications BuildingIowa State UniversityAmes, IA 50011

This publication is printedon recycled paper.

iowa wildlife series - iowa insects, spiders, and other ... · butterflies are toxic to some...

Documents