Download Insects - Green Local Schools

Insects
Chapter 37
The Insect World
Section 37.1
Characteristics of Insects
Three tagmata:
1. Head: mandibles to chew, pair of
antennae for sensory
2. Thorax: 3 pairs of jointed legs, most
have 1 or 2 pairs of wings
3. Abdomen: 9-11 segments
Head
Thorax
Abdomen
Exoskeleton with…
Antennae Examples:
Leg Examples:
Appendage examples:
Two types of mouthparts:
Entomology:
• The study of insects
– & other terrestrial arthropods
• Person = entomologist
– Classify insects into 25 orders based up:
• Mouthparts
• Number of wings
• Type of development
Classification of Insects
• Subphylum: Hexapoda
• Class: Insecta
• Common Orders:
–
–
–
–
–
–
–
–
–
Hemiptera
Homoptera
Isoptera
Odonata
Orthoptera
Coleoptera
Diptera
Hymenoptera
Lepidoptera
Table on
page 743
Success of Insects
• Insects live everywhere (except deep
ocean)
• 1 million species (more than 3x all
other animals!)
– 10 million might exist
• Why so many?
– Ability to fly
• Escape & dispersal
– Small
– Short life spans
• Quick adaptations
Insects and People
• Competition for food 
• Spread diseases 
– Plague, typhoid fever, malaria
• Consume clothing & carpet 
• Crop pollination 
• Make commercial products 
– Wax, silk, honey
• Recycle nutrients 
Insect Development
• Hatchling must go through several
molts to reach adulthood (sexual
maturity)
• Metamorphosis: major developmental
changes from larvae to adult
• Two forms: incomplete & complete
Incomplete Metamorphosis
• Nymph: immature form of insect that
looks like adult
• Only the adult can fly and is sexually
mature
Complete Metamorphosis
• Two stages of development that look
drastically different
• Pupa: changing from larvae to adult
• Cocoon: protective covering of pupa
• Chrysalis: butterfly pupa protection
Insect Defense
• Passive defense examples:
– Camouflage
– Look like plants
• Aggressive defense examples:
– Venomous stingers
– Harmful chemicals
• Warning coloration: color pattern to
warn of poison
Mimicry
• Mullerian mimicry: poisonous species
mimics the coloration of another
poisonous species
– Bees & wasps
• Batesian mimicry: harmless species
mimics the coloration of a poisonous
species
– Monarch & viceroy butterflies
Grasshoppers
Subphylum Hexapoda
External Structures:
• Head = mouthparts, antennae, simple
& compound eyes
• Thorax = 3 parts:
– Prothorax = 1st pair walking legs
– Mesothorax = 2nd pair walking legs &
forewings (protective)
– Metathorax = 3rd pair legs (jumping) &
hindwings (flying)
• Abdomen = upper & lower plates
connected by flexible exoskeleton
– Covered by waxy cuticle (prevents
desiccation)
Feeding
• Chewing mouthparts (feed on plants)
– Labrum: functions like upper lip
– Labium: functions like lower lip
– Mandible: tears food
– Maxilla: helps hold & cut food
Digestive Tract
• Mouth  saliva (from salivary glands)
 esophagus  crop (storage) 
gizzard  midgut/stomach (bathed in
enzymes from gastic ceca)  nutrients
absorbed in hindgut/intestine  anus
Circulation, Respiration, &
Excretion
• Circulatory system:
– Open
– Aorta (large, dorsal vessel)
– Heart (pumping organ)
• Respiratory system:
– Tracheae (site of air diffusion inside body)
– Spiracles (openings to allow air in/out)
• Excretory system:
– Malpighian tubules: return most water
back to hemolymph, rest leaves body via
feces
Neural Control
• CNS = brain, ventral nerve cord, &
ganglia at each segment
• Antennae – touch & smell
• 3 simple eyes – intensity of light
• 2 compound eyes – sight
• Tympanum – sound & communication
• Sensory hairs - touch
Reproduction
•
Separate sexes (male & female)
•
Sexual Reproduction:
1. male deposits sperm into female
seminal receptacles
2. Eggs released from ovaries
3. Internal fertilization
4. Ovipositor: digs a hole in soil to lay
eggs
Insect Behavior
Section 37.2
Communication
• Chemical communication via
pheromones
– Chemical released that affects behavior
or development of other members of
same species
video
• Uses of pheromones:
– Attract mates
– Identify hives
– Food trails
Communication Con’t…
• Sound communication via chirping,
buzzing, etc. (crickets, mosquitoes)
– Attract females
– Protect territories
• Sight communication via flashes of
light (fireflies)
– Find mates
Behavior in Honeybees
•
Social insects: insects that live in
colonies with division of labor
•
Innate behaviors: genetically
determined
– Not taught or learned
•
Three types of honeybees:
1. Worker
2. Drone
3. Queen
Worker Bees
• Sterile females
• First adult week: feed honey & pollen
to queen, drones, & larvae
– Royal jelly
• Next two weeks: secrete wax (build &
repair honeycomb), remove wastes,
guard hive, circulate air in hive
Continued…
• Last weeks of life: collect nectar &
pollen
• Adaptations:
– Barbed stingers for protection of hive
– Mouthparts for lapping nectar
– Legs with pollen packers, baskets, &
pollen combs
Drones
• Males developed from unfertilized
eggs
– Parthenogenesis
• Can travel from hive to hive
• Sole function: deliver sperm to queen
– succeed in mating = death
– penis and associated abdominal tissues
are ripped from the body at intercourse
Queen Bee
• Continuous diet of royal jelly as larvae
= queen bee
• Secretes pheromone “queen factor”
that prevents other females developing
into queens
• Sole role: reproduction
– Mates only once
– Sperm remains inside her for 5+ years
– Lays millions of eggs per year!
The Dances of the Bees
• Dancing performed by scout worker bees
• Round dance: told workers that food was
nearby but not exact location
• Waggle dance: told workers that food
was far away and told location
Altruistic Behavior
• Definition: aiding other individuals at
one’s own risk or expense
• Kin selection: increasing the
propagation of one’s own genes by
helping closely related individuals
reproduce
• Example: worker bee stinging = death