21-1 chapter 21 hexapods hexapods. copyright © the mcgraw-hill companies, inc. permission required...

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CHAPTER 21CHAPTER 21CHAPTER 21CHAPTER 21

HexapodsHexapods HexapodsHexapods

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

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Diversity and CharacteristicsDiversity and Characteristics

Subphylum HexapodaSubphylum Hexapoda Members named for the presence of Members named for the presence of six legssix legs Have Have 3 tagmata3 tagmata

Head Head ThoraxThorax Abdomen Abdomen

AppendagesAppendages attach to head and thorax attach to head and thorax Main class within HexapodaMain class within Hexapoda

Insecta - Insecta - (ex. Ladybugs, grasshoppers, butterflies, walking (ex. Ladybugs, grasshoppers, butterflies, walking stick, ect.)stick, ect.)

Pterogotes: winged insects Pterogotes: winged insects Apterogotes: wingless insectsApterogotes: wingless insects


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Class InsectaClass Insecta

DiversityDiversity Most diverse and abundantMost diverse and abundant of all arthropods of all arthropods Number of known species estimated at 1.1 million, Number of known species estimated at 1.1 million,

but estimated that there but estimated that there may be as many as 30 may be as many as 30 million species worldwidemillion species worldwide

Adaptive TraitsAdaptive Traits Flight and small size makes insects widely Flight and small size makes insects widely

distributeddistributed Well-protected eggs withstand rigorous conditions Well-protected eggs withstand rigorous conditions Most structural modifications are in wings, legs, Most structural modifications are in wings, legs,

antennae, and mouthpartsantennae, and mouthparts Hard, protective exoskeleton well-adapted to life in Hard, protective exoskeleton well-adapted to life in

desert regions - hold in waterdesert regions - hold in water


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External Form and FunctionExternal Form and Function

There are MANY Variations in Body FormsThere are MANY Variations in Body Forms Exoskeleton composed of complex plates, Exoskeleton composed of complex plates,

Muscles attach to plates and allow Muscles attach to plates and allow precise movementprecise movement

HeadHead Large compound eyesLarge compound eyes One pair of antennaeOne pair of antennae

Function in touch, taste, hearingFunction in touch, taste, hearing Mouthparts consistMouthparts consist

Pair of mandibles and maxillaePair of mandibles and maxillae Tongue like Hypopharynx (determines how it feeds.) - Tongue like Hypopharynx (determines how it feeds.) -

ProboscisProboscis



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Different Insect Antennae


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ThoraxThorax Consists of 3 partsConsists of 3 parts Each section has a pair of legsEach section has a pair of legs

WingsWings located on the thoraxlocated on the thorax Veins serve to strengthen the wingVeins serve to strengthen the wing

Vein patternVein pattern used to identify insect taxa used to identify insect taxa



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Legs and adaptationsLegs and adaptations Walking legs end in terminal pads and Walking legs end in terminal pads and

clawsclaws Hindlegs of grasshoppers and crickets are Hindlegs of grasshoppers and crickets are

enlarged for jumping enlarged for jumping Forelegs of praying mantis allow it to Forelegs of praying mantis allow it to

grasp preygrasp prey Honeybees have leg adaptations for Honeybees have leg adaptations for

collecting pollencollecting pollen



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Hindleg of a Grasshopper: Muscle attached to internal wall of exoskeleton


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Praying Mantis front legs are used to grasp prey


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Adaptations in Bee Legs: Spur removes wax,

Pollen brush help remove pollen collected on the bodyPollen comb brushes off pollen collected on other leg

Pollen packer presses pollen into pollen basketBee carries as much pollen as possible back to her hive


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Giant Horned Beetle:Process from head is

used to lift or pry competition from resources.

(Usually competition issame species)

Walking Sticks Mating:They have many predators,

despite camouflage


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A female Wasp usesher abdomen to

thrust her ovipositor into the wood to

make a burrow to lay hereggs. The larva will feed

on the wood


Water strider:Supported by the

Water’s surface tension


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Flight and wingsFlight and wings Insect wings are outgrowths of cuticle from the Insect wings are outgrowths of cuticle from the

thoracicthoracic segments segments Most flying insects have 2 pairs of wingsMost flying insects have 2 pairs of wings

Diptera (true flies) have one pairDiptera (true flies) have one pair Non-reproductive ants and termites are winglessNon-reproductive ants and termites are wingless



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Order Diptera: House Fly Only one set of wings, Contaminated with over 100 pathogens


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Flight Muscles of InsectsFlight Muscles of Insects Direct flight musclesDirect flight muscles attach to wing attach to wing

directlydirectly Indirect flight musclesIndirect flight muscles alter the shape of alter the shape of

the thorax to cause wing movementthe thorax to cause wing movement


Flight Muscle ContractionFlight Muscle ContractionWing beats may vary Wing beats may vary

4/second in butterflies 4/second in butterflies 1000/second in midges1000/second in midges

(small flies)(small flies)


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Internal Form and FunctionInternal Form and Function Digestive SystemDigestive System

ForegutForegut Mouth with salivary glands, esophagus, crop, and Mouth with salivary glands, esophagus, crop, and

gizzardgizzard Midgut (similar to small intestine)Midgut (similar to small intestine)

Primary site of digestion and absorptionPrimary site of digestion and absorption Ceca (villi) may increase digestive and absorptive Ceca (villi) may increase digestive and absorptive

areaarea Hindgut (similar to large intestine)Hindgut (similar to large intestine)

Primarily a site for water absorptionPrimarily a site for water absorption



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Internal Structure of Female Grasshopper


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Most feed on plant tissues or juices and are Most feed on plant tissues or juices and are herbivorousherbivorous

Many caterpillars are specialized to eat only Many caterpillars are specialized to eat only certain species of plantscertain species of plants

Many beetles and other insect larvae eat dead Many beetles and other insect larvae eat dead animalsanimals

Some are predaceous (praying mantis)Some are predaceous (praying mantis)



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Parasitic Insect: Flea


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Parasite: Guinea Pig Lice


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Parasite: Human Lice


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A: Larval Stage of Tomato HornwormB: A tiny wasp laid eggs in

Hornworm Caterpillar. Pupae emerge, Caterpillar dies


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A: Chewing Mouthparts

B: Sucking Mouthparts -Fascicle pierces

D: Sucking Mouthparts Mandible absent, Maxillae form long proboscis

E: Sponging MouthpartsLap liquid, Liquefy food


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Circulation - Open CirculationCirculation - Open Circulation Heart moves hemolymphHeart moves hemolymph

Gas Exchange Gas Exchange Gas exchange while preventing water lossGas exchange while preventing water loss Tracheal systemTracheal system

Network of thin-walled tubes that branch throughout the Network of thin-walled tubes that branch throughout the insect bodyinsect body

SpiraclesSpiracles open to the tracheal trunks open to the tracheal trunks 2 spiracles on thorax and 7–8 on abdomen2 spiracles on thorax and 7–8 on abdomen

Valve Valve on the spiracle on the spiracle Reduces on water loss and may serve as a dust filterReduces on water loss and may serve as a dust filter



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Tracheal System:

Spiracle OpeningPrevent collapse

System provides gasSystem provides gas transport transport without use of oxygen-carrying pigmentswithout use of oxygen-carrying pigments


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Excretion and Water Balance Excretion and Water Balance Insects utilizeInsects utilize Malpighian tubules Malpighian tubules


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Sense OrgansSense Organs MechanoreceptionMechanoreception

Touch, pressure, vibration, etc. are detected by Touch, pressure, vibration, etc. are detected by sensilla sensilla (small hairs)(small hairs)

Distributed widely over antennae, legs, and bodyDistributed widely over antennae, legs, and body Auditory Reception Auditory Reception

Sensitive setae or tympanal organs Sensitive setae or tympanal organs detect airborne detect airborne soundssounds

Organs in legs can detect vibrations of surfaceOrgans in legs can detect vibrations of surface ChemoreceptionChemoreception

Some insects can detect odor from several kilometers awaySome insects can detect odor from several kilometers away



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Visual ReceptionVisual Reception 2 types of eyes: 2 types of eyes: simple simple (sense light)(sense light) and and

compound compound (sense images)(sense images) Most larval stages have simpleMost larval stages have simple Adult stages have compoundAdult stages have compound Some insects can detect colorSome insects can detect color



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Reproduction Reproduction ParthenogenesisParthenogenesis occurs predominantly in some Hemiptera occurs predominantly in some Hemiptera

(true bugs) and Hymenoptera (ants, wasps, bees)(true bugs) and Hymenoptera (ants, wasps, bees) Sexual reproductionSexual reproduction is the norm is the norm Sexes are Sexes are separateseparate Sexual AttractionSexual Attraction

Females secrete a Females secrete a pheromonepheromone to attract males from a to attract males from a great distancegreat distance

Fireflies use flashes of light to detect matesFireflies use flashes of light to detect mates Some insects use sounds, color signals, and other Some insects use sounds, color signals, and other

courtship behaviorscourtship behaviors



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Grasshopper Reproduction

Damselflies Reproduction


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Fertilization usually Fertilization usually internalinternal Sperm may be released directly or packaged into Sperm may be released directly or packaged into

spermatophoresspermatophores Female may only mate once and Female may only mate once and store sperm to store sperm to

fertilize eggs throughout her lifefertilize eggs throughout her life Females may lay a few eggs and provide care of Females may lay a few eggs and provide care of

young, or lay huge numbersyoung, or lay huge numbers Butterflies and mothsButterflies and moths must lay eggs on the host must lay eggs on the host

plant if the caterpillars are to survive plant if the caterpillars are to survive WaspsWasps may have to locate a specific species that is may have to locate a specific species that is

the only host to their youngthe only host to their young



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Mosquito Eggs laid in a “raft”on water Mosquito Larva


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Metamorphosis and GrowthMetamorphosis and Growth Various forms of metamorphosis produce Various forms of metamorphosis produce

degrees of change among different insect groupsdegrees of change among different insect groups Most insects change form after hatching from eggMost insects change form after hatching from egg Each stage between molts is called an Each stage between molts is called an instarinstar Insects develop wings during the last stage Insects develop wings during the last stage



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Ecdysis in cicada: Wings form after last molt

Adult Cicada


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Stonefly and DamselflyBoth have Aquatic Nymphs


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Incomplete MetamorphosisIncomplete Metamorphosis Grasshoppers, cicadas, mantids, true bugs, Grasshoppers, cicadas, mantids, true bugs,

mayflies and dragonflies exhibit this mayflies and dragonflies exhibit this metamorphosismetamorphosis

Young are called nymphsYoung are called nymphs Stages are egg-nymph-adult. All stages look Stages are egg-nymph-adult. All stages look

equivalent, vary in sizeequivalent, vary in size



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Incomplete Metamorphosis: Body forms are similar throughout cycle Young are called nymphs

Incomplete Metamorphosis: grasshoppers, cicadas, mantids,terrestrial bugs, mayflies, stoneflies, dragonflies, and aquatic bugs


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Complete MetamorphosisComplete Metamorphosis AboutAbout 88% of insects88% of insects undergo complete undergo complete

metamorphosismetamorphosis Larva, pupa, and adult vary in body planLarva, pupa, and adult vary in body plan Larvae and adults often live in completely Larvae and adults often live in completely

different environmentsdifferent environments No competitionNo competition

After several larval instarsAfter several larval instars Larval moth or butterfly becomes a pupa inside a Larval moth or butterfly becomes a pupa inside a

cocoon or chrysaliscocoon or chrysalis Pupae often pass the winter in this stagePupae often pass the winter in this stage Final molt occurs and the adult emerges in springFinal molt occurs and the adult emerges in spring

Stages are egg-larva-pupa-adultStages are egg-larva-pupa-adult



21-43Complete Metamorphosis: Multiple life stages


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Diapause Diapause Period of dormancy in the annual life cycle that Period of dormancy in the annual life cycle that

is independent of conditionsis independent of conditions Winter dormancy: Winter dormancy: hibernationhibernation Summer dormancy: Summer dormancy: estivationestivation

Any stage (eggs, larvae, pupae, or adults) may Any stage (eggs, larvae, pupae, or adults) may remain dormant to remain dormant to survive adverse conditionssurvive adverse conditions

Always occurs at Always occurs at end of an active growth stageend of an active growth stage Insect is then ready for another moltInsect is then ready for another molt



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Defense Defense Protective coloration, warning coloration, and Protective coloration, warning coloration, and

mimicrymimicry are protective adaptations are protective adaptations Stink bugs and others have Stink bugs and others have repulsive odors repulsive odors

and tastesand tastes Some insects are Some insects are aggressiveaggressive (e.g., bees and (e.g., bees and

ants)ants) The monarch caterpillar The monarch caterpillar incorporates a incorporates a

poisonous substancepoisonous substance from its food plant, from its food plant, milkweedmilkweed

The bombardier beetle can spray an attacking The bombardier beetle can spray an attacking enemy with enemy with irritating chemicalsirritating chemicals



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Mimicry in butterflies:A: Monarch - is distasteful

B: Viceroy Butterfly - mimics monarch to avoid predators


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Crypsis - Camouflage in shape or colorationA: Resembles a dead leaf (moth)

B: Resembles a tree branch (treehopper)C: Resembles leaves (Katydid)


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Dung Beetles:Chew off a bit of dung,

Roll it to site to bury, Eggs laid in ball,

Larvae feed on dung

Behavior and CommunicationBehavior and Communication


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PheromonesPheromones Chemicals secreted by one individual to affect the Chemicals secreted by one individual to affect the

behavior of another individualbehavior of another individual Attract the opposite sex, trigger aggregation, fend off Attract the opposite sex, trigger aggregation, fend off

aggression, and mark trailsaggression, and mark trails Bees, wasps, and ants can recognize nestmates and Bees, wasps, and ants can recognize nestmates and

signal an alarm if strangers enter the nestsignal an alarm if strangers enter the nest Sound Production and ReceptionSound Production and Reception

Sounds are used as warning devices, advertisement of Sounds are used as warning devices, advertisement of territory, and courtship songs.territory, and courtship songs.

Crickets chirp for courtship and aggressionCrickets chirp for courtship and aggression


Behavior and CommunicationBehavior and Communication


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Firefly femme fatale:Uses false mating signals

to attract male


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HoneybeesHoneybees Have a few Have a few male drones,male drones, a a fertile female queenfertile female queen

and many and many female workersfemale workers Drones develop by parthenogenesis (virgin birth) Drones develop by parthenogenesis (virgin birth) Development of a fertile queen requires ingestion Development of a fertile queen requires ingestion

of of “royal jelly” for 6 days or more“royal jelly” for 6 days or more Queen secretes Queen secretes “queen pheromone”“queen pheromone” to prevent to prevent

workers from maturing or feeding larvae royal jellyworkers from maturing or feeding larvae royal jelly A honeybee hive may contain 60,000–70,000 A honeybee hive may contain 60,000–70,000

individuals individuals Scouts inform workers on location of foodScouts inform workers on location of food


Social BehaviorSocial Behavior


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Queen Bee surrounded by her court.Queen is only Egg layer.

Others are attracted to phermones, Lick her body and transfer phermones.


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Termites

Termite workers are wingless Queen continuously lays eggs.


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Ants Ants In ant colonies, the male ant dies after matingIn ant colonies, the male ant dies after mating Ants have wingless soldiers and workersAnts have wingless soldiers and workers Ants have also evolved striking patterns of Ants have also evolved striking patterns of

“economic” behavior: “economic” behavior: making slaves, fungus making slaves, fungus farming, sewing nests together, tool use, and farming, sewing nests together, tool use, and herdingherding



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Ant Nest

Ant feeding on Aphids


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Insects and Human WelfareInsects and Human Welfare

Beneficial InsectsBeneficial Insects Insects produce honey, beeswax, silk Insects produce honey, beeswax, silk Of more economic importance, bees Of more economic importance, bees pollinate $10 pollinate $10

billion worth of food crops in the U.S. annuallybillion worth of food crops in the U.S. annually Dead animals rapidly consumed by fly maggots Dead animals rapidly consumed by fly maggots Insects are Insects are critical components of most food critical components of most food

chainschains and an important food source for many and an important food source for many fish and birdsfish and birds


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Stink bug feeds on caterpillar by using

proboscis

Ladybug feeds on Mites, Aphids and

Other pests.

Parasitic wasp: Inserts eggs into cricket,

Eggs develop into larvaAnd feed on cricket


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Harmful InsectsHarmful Insects Harmful insects eat and destroy plants and Harmful insects eat and destroy plants and

fruitsfruits Nearly every cultivated crop has several Nearly every cultivated crop has several

insect pestsinsect pests Requires substantial money for insect Requires substantial money for insect

controlcontrol Insects also destroy food, clothing, and Insects also destroy food, clothing, and

propertyproperty



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Japanese Beetle:Feeds on Fruits and Flowers

Mealybug: Ruins crops

Corn Ear Worm:Ruins Corn Crops


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Medically important insects include Medically important insects include vectors for disease agentsvectors for disease agents

Malaria, West Nile, Filarial diseasesMalaria, West Nile, Filarial diseases are are carried by mosquitos carried by mosquitos Most common major world diseaseMost common major world disease

Fleas carry the Fleas carry the plague plague (bacteria)(bacteria) The tsetse fly carries The tsetse fly carries african sleeping african sleeping

sickness sickness (protozoan)(protozoan) Lice carry Lice carry Typhus fever Typhus fever (parasitic worm)(parasitic worm)



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Mosquito: Vector for Malaria, West Nile Virus, Filarial diseases

21-1 chapter 21 hexapods hexapods. copyright © the mcgraw-hill companies, inc. permission required...

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