Insects

Learning Target Objectives:

•Differentiate between Batesian and Mullerian mimicry•Compare/contrast arthropods to other invertebrate animals.•Compare and contrast incomplete with complete metamorphosis•Evaluate the role/impact of insect vectors, and the diseases they carry, on human life.•Evaluate various types of insect defense and survival strategies/adaptations, including anatomical and physiological components

Vocabulary:

Entomology * thorax * labrum * labium * mandibles * maxilla * compound eye * ocelli * tympanum * femur * tibia * fibula * tarsus * forewings * hindwings * esophagus * crop * gizzard * anus * malpighian tubules * spiracles * tracheae * ovipositors * incomplete & complete metamorphosis * nymph * larva * pupa * instar * cocoon * chrysalis * probosis * mullerian & batesian mimicry

InsectsPhylum: Arthropoda

Subphylum: Uniramia

Class: Insecta

- have survived for over 300 million years (since BEFORE dinosaurs!)

- open circulatory system

- exoskeleton

- jointed appendages

- segmented body, 3 parts: head, thorax (chest region) , and abdomen

- 1 pair of antennae on head

- 3 pair of jointed legs attached to the thorax and POSSIBLY 1 or 2 pair of wings

- abdomen has 11 segments

Entomology – study of insects

There are more than 900,000 species of insects.

Success of Insects

- flight (in some): flee enemies, find food further away, inhabit new environments

- reproduce quickly/short life cycle: adaptations can occur each generation so can adapt rapidly to changing environment (Natural Selection), large numbers of oofspring are produced also increasing genetic variability in populations

- variety of adaptations for feeding, etc. and a variety of nutritional requirements eliminate most competition

- small size means less area needed to survive

Insects as Disease Vectors

Mosquitoes – carry:

malaria (“Anopheles” carries malaria. We have mostly “Aedes” & “Culex”) Malaria kills huge numbers of people in tropical areas.

Yellow Fever (a viral infection) Many building Panama canal died.

West Nile (even people and animals in Wisconsin have died)

Rat Flea – Bubonic or Black Plague killed 1/4th of Europe’s population in 14th century (25 million people). Of 992 cases in US between 1900 & 1972, 720 were fatal. (“BaaBaa Black Sheep” came from this disaster)

Lice – carry typhus (not typhoid fever which is spread by water & flies) Typhus causes high fever, delirium, blotchy rash, & death. (It’s related to Rocky Mountain Spotted Fever) – fall of Napolean’s army

Houseflies – carry dysentery & typhoid fever

Tsetse fly - carries African Sleeping Sickness

The Grasshopper

Mouthparts:

1) Labrum – upper “lip”

2) Labium – lower “lip”

3) Mandibles – chewing jaws, move side-to-side

4) Maxilla – help hold food

Grasshopper Anatomy

- 2 compound eyes (multiple lenses – see in several directions at one time)

- 3 simple eyes (ocelli) – sense light

- 2 antennae

- tympanum – used for hearing, located on abdomen just above jumping legs

The legs:

- 4 front = walking legs

- 2 back = jumping legs

Femur = upper leg, Tibia = lower leg, tarsus = foot

Wings:

Forewings – leathery, used for gliding & for protecting hind wings

Hindwings – used for flight

Digestive System:

Mouth (with salivary glands) esophagus (elastic tube) crop (stores food) gizzard (grinds food with chitinous plates) midgut (stomach) hindgut (colon/intestine) & rectum anus

Excretory System:

Malpighian Tubules – filter blood of liquid wastes rectum out anus

Respiratory System:

No lungs or gills !!!

Spiracles – openings on abdomen & thorax where air enters as muscles expand body

Tracheae – carry oxygen from spiracles directly to tissues & also collects carbon dioxide from tissues to exhale them

Reproductive System:

Male deposits sperm in female’s seminal receptacle where it is stored until egg release (internal fertilization). The female deposits the eggs in the soil using ovipositors.

Section 28-1

Ventral View

Antennae

Compound eyeBrain Digestive

tract Malpighian tubules

Heart

Reproductive organs

Anus

SpiraclesTrachealtubes

Nervecord

Ganglia

Salivaryglands

Mouth

Tracheal tubes

Spiracles

Legs

Anatomy of a Grasshopper

Development/metamorphosis:

Incomplete metamorphosis – developmental changes where the egg hatches into a miniature, immature adult look-alike with NO wings. This is a nymph. The nymph molts several times until sexual maturity (adulthood). Typical of grasshoppers and termites.

Complete metamorphosis – major changes occur as an egg hatches into a larva which grows and molts several times before becoming a pupa (“resting” stage) where larval tissue breaks down and a mature adult develops. Ex: moths, butterflies, flies, etc. (over 80% of insects)

egg

adult larva

pupa

Butterflies and Moths

Larva is a caterpillar – eat leafy foods (usually), molt about 4 times, each stage is called an instar.

Pupa is a cocoon spun of silk for a moth but a chrysalis, made from the hardening of “skin” after the last molt, for butterflies.

Differences in adults usually include:

Moths Butterflies

Feathered antennae (esp. males) Club antennae

Night flights Day Flights

Somewhat wooly bodies Non-wooly bodies

Both adult types suck food using a probosis (like a straw or an elephant’s trunk). Adults feed on nectar, rotting fruit, or dung. They taste things with their hind feet!

Larva require lots of food for growth, adults need lots of energy for flight & reproduction. Metamorphosis allows the different forms to meet their needs without competing.

Insect defense:

- stingers (bees, wasps)

- noxious chemicals (beetles, some caterpillars)

- camouflage (walking sticks, etc.)

- mimicry

Mimicry:

Mullerian mimicry – many “poisonous” insects take on the same warning coloration to keep away predators (Ex: bees, hornets, etc. are usually all yellow and black)

Batesian mimicry – nonpoisonous insects imitate poisonous insects in coloration (Ex: Viceroy (non-toxic mimics Monarch which is toxic)

Monarch: Viceroy:

Comparison of Arthropods

1) Trilobita 2) Crustacea

-extinct (lived in warm, a) 10 legs (8 walking legs, 2

tropical water – oldest known chelipeds for crayfish)

animal fossils b) 2 body regions

c) breathe with gills (attached

3) Arachnida to legs)

a) 8 legs d) compound eyes

b) 2 body regions usually Exs: crayfish, crabs, lobster

c) breathe with simple lungs

d) simple eyes 4) Insecta

e) no antennae a) 6 legs

Ex: spiders, mites, ticks, b) 3 body regions

horseshoe crabs c) breathe with tracheae

d) mostly compound eyes

Ex: grasshoppers, lice, moths