Transcript Introduction

Entomology
Biol 405/405L
Holly Downing, PhD
LSB 111
Introduction
• Handout
– Course expectations
• Collection methods
– Supplies distributed
Charles Darwin inspecting collected during the
voyage of the Beagle. (After various sources,
especially Huxley & Kettlewell 1965 and
Futuyma 1986.)
What is an insect?
• Animal Classification
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Domain
Kingdom
Phylum
Class
Order
Family
Genus
Species
Eukarya
Animalia
Arthropoda
Insecta
Hymenoptera
Vespidae
Mischocyttarus
drewsenii
Kingdom Animalia
Invertebrates
• 95% of Animal Kingdom
• Multicellular, eukaryotes
• Sponges – most primitive
– Cells, but no organized tissues
• Jellyfish – 2 tissue layers
• Other invertebrates and
vertebrates have 3 tissue
layers
• Coelom – body cavity
– Arthropoda one of several phyla
Vertebrates
• 5% or less Animal Kingdom
• Includes animals with
vertebral column
– Some Chordata are
considered Invertebrates
Phylum Arthropoda
• Invertebrate animals
with jointed legs
• Exoskeleton made of
chitin
• Molt exoskeleton as
grow
• Active due to jointed
legs
• All types of habitats
• Very successful group
Figure 1.1
Speciescape, in which the size of individual organisms is approximately proportional to the number of
described species in the higher taxon that it represents. (After Wheeler 1990.)
Entomology
• Entomologists study
insects
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Anatomy and Physiology
Ecology
Evolution
Behavior
Diversity, species
richness
– Genetics
– Biochemistry
• Insects make excellent
research models
– Easy to rear
– Short generation time
– Simpler anatomy,
neurophysiology
– Very diverse, in all but
under water ocean
habitats
– Simple to complex
behavior
Importance of Insects
A mature larva of the palm weevil, Rhynchophorus
phoenicis (Coleoptera: Curculionidae), a
traditional food item in central Angola, Africa.
(Larva after Santos Oliveira et al. 1976.)
• Research
• Food – nonhumans, too
• Products such as honey,
dyes, shellac
• Work such as pollinators,
predators
• Competitors for crops
and spread diseases
• Spread diseases in
humans, livestock and
pets
Ecosystem function
• Nutrient recycling
• Plant propagation
• Maintenance of plant
community balance
• Important source of
food for other animals
(and some carnivorous
plants)
• Maintenance of animal
community structure
Where are insects found?
• Antarctic: 2 spp of fly
– Bird fleas, lice
– Seal lice
• Arctic: 300 spp. Mostly
flies
• Himalayan mts: 1920,000 ft. elevation
there are permanent
residents
• In air: most spp can fly
• Deep caves, hot springs,
salt lakes, pools of
petroleum
• 3% freshwater spp
• 0.1% intertidal zone
– One water strider lives
on surface of open
ocean
– None in deeper water of
ocean
Why So Diverse and Successful?
• Why not in oceans?
– Entered terrestrial habitat
before other types of
organisms
– Arthropod body already
had exoskeleton and
jointed legs that would
support movement on
shore
• Also, protects from
desiccation
• Internal fertilization
• Chorion protects egg
Ocean niches filled with
Crustaceans, another successful
Arthropod group
Why So Successful?
• Entered terrestrial habitat • Flight
before vertebrates
– Avoid predation (before
• Small size
there were birds)
– Short generation time
– Great reproductive
capacity as a result
– High fertility
– Population explosions can
overwhelm predators
– Natural selection can work
quickly
– Easily dispersed on wind
– Can travel farther, faster
– < 1% are flightless
• Holometabolous
– Most successful groups
– Ability to use multiple
niches
– Ex. Flies: maggot in
garbage or dung; adult is
free flying
Why So Successful? (Con’t)
• Social Behavior
– Animal biomass in
tropical rainforests:
• Insects = 50%
• Social insects = 80% of
insect biomass!
– Cooperative defense &
brood care
– Increased foraging
efficiency
– Can utilize resources that
single individuals can’t
access
Evolution of Insects
• Onychophora – velvet
worms
– Probably similar to first
arthropods
– About 80 spp today
– 1.5-15 cm long
– Moist, tropical areas
– Similar to fossils from
Cambrian (500 mya)
– Segmented with
appendages on each
segment
-- Cuticle; molts as grows
-- Chitin in jaws and leg claws
-- Open circulatory system
-- Tracheal respiratory system
Evolution of Insects (con’t)
• Body plan: consolidation
of segments
– Head, thorax, abdomen
– Head : 6 segments
• Appendages became
mouthparts & antennae
• Segment ganglia became
enlarged to form brain
• Segments fused
1 – labrum (pre-oral)
2 – antenna
3 – lost (brain section there)
4 – mandibles
5 – maxillae
6 - labium
Mouthparts also have sensory
palps
So head = centralized neural
processing, sensory input, and
food intake
Evolution of Insects (con’t)
• Thorax: 3 segments
– Legs (3 pr) & wings (2 pr)
– Strong muscles that attach
to infoldings of
exoskeleton
• Abdomen: 11 segments
– Lost most appendages
– Some modified for penis
or ovipositor
• This is basic plan, but
there’s a lot of diversity
Insect Conservation
• Umbrella effect of
flagship species
– Flagship rarely insects
– But they can benefit
• Some exceptions
– Butterfly and moths
• Monarch butterflies
• El Segundo blue of LA
sand dunes
• Queen Alexandra’s
birdwing
Other showy species such as beetles
and dragonflies or economically
important species such as bees can
be flagship species as well.
Insect Conservation (con’t)
• Habitat conservation
– Many species protected
– Species interactions are
important
– Need to know about the
often complex ecology
and interrelationships
among species for this
approach to be
successful
• Keystone species are
those that have a large
influence on an
ecosystem and the
communities of species
– Usually think of this as a
vertebrate or plant spp
– But some insects can
have major impacts
• Termites, bees, ants
Box 1.1
Example of complex habitat requirements
– Large Blue and ant host in southern England