Insects

External External AnatomyAnatomy

headhead abdomenabdomenthoraxthorax

Adult insects are known for having three major body regions, six legs, one pair of antennae and usually two pair of wings as adults.

from the 1995 Physiology or Medicine Nobel Poster

Adult insects develop as a composite of fused segmentswith specific body part associations.

head

mouthpartsmouthparts

antennaeantennaecompoundcompound eyeseyes

HEADHEAD

The first body region is the head. Insect heads can behighly variable, but most possess eyes, antennae and mouthparts.

AntennaeAntennae

June beetleJune beetletermitetermite

flyflybutterflybutterflyantant

beetlebeetle

Antennae are used by insects as major sensory devices, especially for smell, and can be adaptive for the insect in many ways.

Two Examples of Two Examples of MouthpartsMouthparts

chewingchewing piercing/suckingpiercing/suckingInsect mouthparts are also highly modified for theinsect. Chewing, biting, or sucking, are a few examples. Mouthparts of an immature insect may differ from those of the same insect in its adult stage.

Arthropod Vision

• Simple eyes – Light sensitive cells

share a common lens

• Compound eyes– Thousand of closely

packed units called ommatidia

Simple ocelli.Complex lensed ocelli.Compound eyes made of ommatidia.

Compound & Simple Eyes

Picture of bodyparts

ThoraxThoraxThe middle body region is called the thorax and is composed of three fused segments. All legs and wings are located on the thorax.

LegsLegssuction

diggingdigging swimmingswimming

graspinggrasping

Like the mouthparts and antennae, insect legs are quitevariable in form and function and reflect the insect's lifestyle.

Walking involves the coordinated movement of uniramous appendages in different planes.

Walking

Subphylum Myriapoda Millipedes (Class Diplopoda) have two legs per segment on each side. Slow but powerful.

Centipedes (Class Chilopoda) have one leg per segment on each side. Fast but not as powerful.

Walking

Flying

Hemipterans (flies)Indirect flight muscles allow wings to beat faster than neural transmission. Dorsoventral and longitudinal muscles.Flexible thorax.

AbdomenAbdomenThe last body region is called the abdomen. It is composed of many segments connected by flexible sections allowing it great movement.

Insects possess an exterior covering called the exoskeleton. They do not have internal bones. This segmented "shell" is what gives insects shape and can be very hard in some insects. It is often covered with a waxy layer and may have "hairs" called setae.

Exoskeleton x-sec Exoskeleton x-sec

waxy layerwaxy layerseta seta ( hair hair)

cuti

cle

cuti

cle

InternalInternalAnatomyAnatomy

Inside the insect we find the systems for respiration, circulation, nerves, and digestion, but there is little resemblance to the same systems found in man or other mammals.

Digestive sys

Digestive SystemDigestive System

foregutforegut

midgutmidgut

hindguthindgut

The digestive system is a tube that opens at the mouth and empties at the tail end of the insect. It is divided into three parts called the foregut, midgut, and hind gut. In some insects such as the honey bee, the foregut acts as a crop to carry or hold liquids which can be regurgitated later.

Circ system

Circulatory SystemCirculatory Systemaortic pumpsaortic pumps“ “ heart ”heart ”

The circulatory system is not composed of a central heart, veins and arteries which circulate blood cells and transport oxygen. The insect circulatory system is a simple tube down the back which is open at both ends and slowly pulses body fluids and nutrients from the rear of the insect to the head.

Nervous system

Nervous SystemNervous Systemnerve bundlesnerve bundles

two lobed braintwo lobed brain

(ganglia)(ganglia)

Insects have a less centralized nervous system than humans. The nerve chord runs along the ventral or bottom aspect of an insect. The brain is divided into two main parts. The largest lobes control important areas such as the eyes, antennae, and mouthparts. Other major concentrations of nerve bundles called ganglia occur along the nerve chord and usually control those body functions closest to it.

The respiratory system is composed of air sacs and tubes called tracheae. Air enters the tubes through a series of openings called spiracles found along the sides of the body. The largest spiracles are usually found on the thorax where greater musculature from wings and legs require more oxygen. There are no spiracles on the head.

spiraclesspiracles trachealtrachealtubestubes

RespiratoryRespiratorySystemSystem

“Brain” is 2-3 ganglia with specific functions.Ganglionated ventral nerve cord.

Sense organs (sensilla) protrude out of cuticle.

Can be slit in cuticle.Membranous drums.Chemoreceptors with thin cuticle.

How do Arthropods reproduce and develop?

Most gonochoristic with formal mating and internal fertilization.

LifeLifeCyclesCycles

The many diverse orders of insects have four different types of life cycles. These life cycles are called "metamorphosis" because of the changes of shape that the insects undergo during development.

Without meta

Without MetamorphosisWithout Metamorphosiseggegg adultadultnymphsnymphs

The first type is "without" metamorphosis which the wingless primitive orders such as silverfish (Thysanura) and springtails (Collembola) possess. The young resemble adults except for size.

Incomplete meta

Incomplete MetamorphosisIncomplete Metamorphosiseggegg naiadsnaiads adultadult

The second type is "incomplete" metamorphosiswhich is found among the aquatic insect orders such as mayflies (Ephemeroptera) and dragonflies (Odonata).

Gradual MetamorphosisGradual Metamorphosis

eggegg nymphsnymphs adultadult

The third type is "gradual" metamorphosis seen in such orders as the grasshoppers (Orthoptera), termites (Isoptera), thrips (Thysanoptera), and true bugs (Hemiptera). This life cycle starts as an egg, but each growth, or nymphal stage looks similar, except it lacks wings and the reproductive capacity that the adult possesses.

Complete MetamorphosisComplete Metamorphosis

eggegg larvaelarvae pupapupa adultadult

The fourth type is "complete" metamorphosis found in butterflies (Lepidoptera), beetles (Coleoptera), flies (Diptera), and bees, wasps, and ants (Hymenoptera). This life cycle has the four stages of egg, larva, pupa, and adult. Each stage is quite distinct.

recently molted roachrecently molted roach

It should be noted that because insects are hard-bodied, they cannot grow larger gradually. Instead they grow larger in steps by shedding the hard exoskeleton for a brief period of expansion. The brief periods between or within stages are called molts. Insects are soft-bodied and vulnerable during this time.

• Secretion of "molting fluid" to dissolve old endocuticle.

• New cuticle formed under old exocuticle.

• Break out of old cuticle– Old cuticle breaks at

line of weakness

Molting

Growth stages

• Arthropod passes thru 3-20+ growth stages in life cycle.

• Some stop molting as adults (insects, most spiders)

• Some continue to molt (crayfish, tarantulas)

Soldier Beetles

Order ColeopteraFamily Cantharidae

Life History: Adultson flowering shrubsand trees. Larvaein soil.

Prey: Aphids, locust eggs, snails, slugs, millipedes, earthworms, caterpillars, and maggots.

David Laughlin

Ground BeetlesOrder ColeopteraFamily Carabidae

Life History: Nocturnal, in or on soil, some live up to four years.

Prey: Caterpillars, soil and tree insects, earthworms.

Top: Harpalus sp.Bottom: Calosoma sp. Vera Krischik

Tiger BeetlesOrder ColeopteraFamily Cicindellidae

Life History:Stalkingpredators,fast runners.

Prey: Whateverthey can catch.

John Davidson

Rove BeetlesOrder ColeopteraFamily Staphylinidae

Life History: Nocturnal predators.

Prey: Soil-dwelling insects.

Lady BeetlesOrder ColeopteraFamily Coccinellidae

Life History: Many species, both larvae and adults are predaceous.

Prey: Aphids, scale insects, mealybugs, whiteflies, spider mites, insect eggs.

Jeff Hahn

Pink Lady Beetle (Coleomegilla maculata), a native lady beetle

Convergent Lady BeetleOrder ColeopteraFamily CoccinellidaeHippodamia convergens

Life History: Native and common in the Midwest; larvae and adults are both predaceous.

Prey: Aphids.

John Davidson

Multicolored Asian Lady BeetleOrder ColeopteraFamily CoccinellidaeHarmonia axyridis

Life History: Introduced, invades homes in fall.

Prey:Aphidsandscales.

John DavidsonJohnDavidson

John Davidson

Robber FliesOrder DipteraFamily Asilidae

Life History: Larvaelive in soil anddecaying wood;adults are fast fliers.

Prey: Butterflies, wasps, bees, dragonflies, grasshoppers, beetles, and other flies. Larvae feed on soft-bodied insects such as grasshopper eggs, white grubs, and other insect larvae.

Whitney Cranshaw

Gall Midges

Order DipteraFamily Cecidomyiidae

Life History: Tiny adults feed on honeydew and nectar, larvae are predaceous. Prey: Larvae feed on aphids, mites, scales, whiteflies, and thrips.

Top and bottom: Aphidoletes aphidimyza feeding on aphids

Whitney Cranshaw

Syrphid or Hover Flies

Order DipteraFamily Syrphidae

Life History: Adultsfeed on nectar andpollen. Larvae arepredaceous. One generation every 2 to 4 weeks. Prey: Larvae feed on aphids, scales, and other insects.

David Laughlin

Tachinid FliesOrder DipteraFamily Tachinidae

Life History: Adultslay eggs on plants orhosts. Larvae developinside hosts and pupate in 4 to 14 days. One or more generations per year. Prey: Caterpillars, adult and larval beetles, sawfly larvae, true bugs, grasshoppers, and others.

John Davidson

Minute Pirate Bugs

Order HemipteraFamily Anthocoridae

Life History: Onegeneration takes20 days to complete,multiple generationsper year.

Prey: Spider mites, insect eggs, aphids, thrips, scales, caterpillars.

Orius insidiosus adult

Seed and Big-Eyed BugsOrder HemipteraFamily Lygaeidae

Life History: Many Lygaeids feed on plants, but some are predaceous.

Prey: Insect eggs, aphids, mealybugs, spider mites, leafhoppers, plant bugs, whiteflies, caterpillars, and beetle larvae. Top and bottom: Geocoris species

John Davidson

Pirate BugsOrder HemipteraFamily Miridae

Life History: Most mirids feed on plants, but some are predaceous.

Prey: Mites and plant-feeding insects; lace bugs, cotton aphid, tobacco budworm.

Top: Deraeocoris nebulosus adultBottom: Pirate bug adult (L) and nymph (R)

David Laughlin

John Davidson

Stink BugsOrder HemipteraFamily Pentatomidae

Life History: Most feedon plants, but someare predaceous. Manydischarge a distastefulsmell when handled.

Prey: Caterpillars and beetles such as Colorado potato beetle and Mexican bean beetle.

Predatory stink bug feeding on elm leaf beetle larva

Whitney Cranshaw

Stink Bugs

CW from top left: Podisus maculiventris adult attacking tussock moth caterpillar, Perillus bioculatus nymph feeding on beetle larva, P. bioculatus nymph feeding on hornworm John Davidson

Whitney CranshawDavid Laughlin

Assassin BugsOrder HemipteraFamily Reduviidae

Life History: Assassin bugs feed by piercing prey with their beaks to suck out juices.

Prey: Caterpillars, small flying insects, aphids, and leafhoppers.

Wheel bug (Arilus cristatus)

Aphelinid WaspsOrder HymenopteraFamily Aphelinidae

Life History: Solitary,lay eggs in or outsidehosts. Femalesusually reproduceparthenogenetically,males are rare.

Prey: Aphids, mealybugs, psyllids, scales, and whiteflies.

Encarsia formosa adult

John Davidson

Braconid WaspsOrder HymenopteraFamily Braconidae

Life History: Lifecycle is 10–14 days.Larvae are internalparasitoids; manypupate outside hosts. More females than males.

Prey: Aphids, larvae of beetles, flies, sawflies, and caterpillars; tomato hornworm, imported cabbageworm, gypsy moth.

John Davidson

Chalcid Wasps

Order HymenopteraFamily Chalcidae

Life History: Larvae are internal parasitoids of other insects.

Prey: Moths, butterflies, beetles, flies, other wasps.

John Davidson

David Laughlin

Encyrtid WaspsOrder HymenopteraFamily Encyrtidae

Life History: Larvae are parasitoids;adults live 2–3 days.

Prey: Ticks, insect eggs, larvae, and pupae; beetles,bugs, moths, mealybugs, scales.

Top: Encyrtus fuscus reared from hemispherical scaleBottom: Parasitized hemispherical scales turned black

John Davidson

John Davidson

Ichneumonid WaspsOrder HymenopteraFamily Ichneumonidae

Life History: Larvae areinternal or externalparasitoids.

Prey species: Larvae and pupae of beetles, wasps, and caterpillars; armyworms, cabbage looper, fall webworm, oakworms, tent caterpillars, tussock moths, European corn borer.

Whitney Cranshaw

Scelionid Wasps

Order HymenopteraFamily Scelionidae

Life History:Larvae are internalparasitoids of otherinsects and spiders.

Prey: Insect and spider eggs, especially those of true bugs and moths.

John Davidson

Trichogramma WaspsOrder HymenopteraFamilyTrichogrammatidae

Life History: Larvaeare internal parasitoidsof other insects.

Prey: Sawfly and moth eggs; cabbageworm, tomato hornworm, corn earworm, codling moth, cutworm, armyworm, cabbage looper, European corn borer, tomato fruitworm.

University of California at Berkeley

Vespid WaspsOrder HymenopteraFamily Vespidae

Life History: Many have annual colonies with queens, workers, and males.

Yellowjacket with caterpillar

Paper wasp (Polistes species)

Prey: Caterpillars and other insects. May bother people at picnics.

John Davidson

Ants

Order HymenopteraFamily Formicidae

Life History: Annual colonies with queens, workers, and drones (males).

Prey: Otherarthropods, aswell as pollen,nectar, andhuman food.

Workers with eggs Jim Occi, BugPics, www.insectimages.org

Ants

Clemson University, USDA Cooperative Extension Slide Series, www.forestryimages.org

Above: Carpenter ant(Camponotus sp.)

Right: Red imported fire ants (Solenopsis invicta)

with cerambycid larvaeHerbert A. "Joe" Pase III, Texas Forest Service, www.insectimages.org

Green LacewingsOrder NeuropteraFamily Chrysopidae

Life History: Oval,white eggs laidsingly on stalks 8 mm long. Small gray larvae spin cocoons and pupate on undersides of leaves when they are 10 mm long. One to ten generations per year.

Prey: Larvae feed on aphids and other small insects. Adults feed on honeydew and pollen.

Brown Lacewings

Order NeuropteraFamily Hemerobiidae

Life History: Oval,white eggs laid singly.Small gray larvae spincocoons and pupate on undersides of leaves when they are 10 mm long. One to ten generations per year.

Prey: Mites, aphids, mealybugs, scales, whiteflies, and other soft-bodied arthropods.

John Davidson

Mantidflies

Order NeuropteraFamily Mantispidae

Life History: Nocturnalinsects that resemblemantids. Both larvaeand adults are predaceous.

Prey: Spider egg sacs, bee and wasp larvae.

David Laughlin

Predatory Thrips

Order ThysanopteraFamilies Aleolothripidaeand Phlaeothripidae

Life History: Sexual orasexual reproduction.Nymphs resemble adults in size and color. Several generations per year.

Prey: Pest thrips, aphids, mites, whiteflies, and other soft-bodied insects.

John Davidson

Centipedes

Tree of Lifehttp://tolweb.org/tree/phylogeny.html

Tree of Lifehttp://tolweb.org/tree/phylogeny.html

Class Chilopoda

Life History: Nocturnal; in gardens and houses.

Prey: Small arthropods.

Left: Lithobius forficatuAbove: House centipede (Scutigera coleoptrata)