Insect Diversity Download

Why Study Terrestrial Arthropods?
1. Apods more species richness than any
other phylum ( hyper diverse)
2. Apods consistent up to 80% of all animal
3. About 1 million described species.
Various studies say 3-5 while others
studies say about 80million species
1. To compare 50,000 vertebrate species.
That is Fish, reptiles, birds and mammals
make up 50,000 total described species
Why Study Terrestrial Arthropods?
4. Key players in terrestrial ecosystems.
Found in basically all terrestrial
region/habitat except Polar Regions.
5. Dominate abundance ( # of individuals)
and biomass
6. Pollination, most flowering plants depend
on animals for pollination and most
pollinators are insects.
• Insect pollinators
are responsible for
1/3 of food in the
grocery store.
• Many of the fruit that
you take for granted
require insect
pollination: Apple,
Pears, Japanese
Plums, and
Cherries. Includes
Nuts as well.
Why Study Terrestrial Arthropods?
7. Plant herbivores = phytophagous (plant
feeding) insects. Controls plant
8. Detritivores = important in decomposition
of organic material ( dead stuff)
– Returns nutrients back to system
Why Study Terrestrial Arthropods?
9. Prey items – important to essentially all
terrestrial food web.
10. Parasites of most vertebrates and
majority of arthropods themselves have
arthropod parasites
Impacts on human welfare
Negative impacts
1. Vectors for disease ( transmission of west Nile
virus and many others)
2. Parasites on humans ( fleas, mites, ticks)
3. Dangerous allergies and venoms
1. Cause medical problems
4. Crop loss ( phytophagous insects)
5. Invasive species ( Argentine Ants) cause the
loss of other species
Parasites on humans
Impacts on human welfare
Positive Impacts
1. Ecosystem services
Processes of decomposition
Nutrient cycle
Bio Control – use natural predators or parasites
to control pests.
5. Important to the health of terrestrial ecosystems
2. Nutrition yum!
Impacts on human welfare
Positive Impacts
3. Intrinsic molecules
1. Silks
2. Venoms
3. Anti microbial
4. Forensics – forensic entomology - Use
changes in insects’ ecology and life cycle
to help solve crime.
See video
Insect Classification
3 Key Insect Characteristics
• 3 body segments (Head, thorax, abdomen)
• 3 pair of legs
• 1 pair antenna
Wings present sometimes reduced or absent
Subphylum Insecta
Key to Insect Dominance
• We will look at the following topics to
answer the question above
– Factors that promote speciation
– Ecological divergence
Key to Insect Dominance
1. Evolution of wings
– Utilize new or scarce resources
• E.g. flowers, most pollinators fly
– Dispersal to new habitat
– Escape unfavorable environment
Key to Insect Dominance
2. Complex metamorphosis
– Immature stages morphologically different
from adults and therefore utilize different
resources and habitats this reduces
competition with in species (ecologically
divergent and lineage persistence
Key to Insect Dominance
3. Short generation time
– Novel genetic variations arise per generation
• Most insects have many generations per unit of
time which equals lots of genetic variations
Genetic Variation is the stuff of evolutions
Most insects live less than a year.
Key to Insect Dominance
Diversification of Mouthparts
– Allow for a variety of food sources
(predation, herbivory, etc.. . .)
Key to Insect Dominance
5. Terrestrial Reproduction
Dessicant resistant eggs help sustain insect
populations despite changing environments
Insect Diversity
More described species of insects than all other
animal species combined
Subphylum Uniramia is made up of five classes
(1st 4 are collectively called Myriapods):
Class Diplopoda
Class Chilopoda
Class Pauropoda
Class Symphyla
Class Hexapoda
Insect Diversity
Class Diplopoda – Millipedes
10 to 100 trunk segments fused together = two pairs of
appendages, ganglia, etc
Feed on decaying plant materials; some suck on plant
juices; few are carnivorous
Adaptations include rolling into balls and chemical
repellants; lack waxy cuticle
Reproduction occurs via sperm transport to females
using gonopods/spermatophores; eggs are fertilized,
laid and hatched.
Insect Diversity
Class Chilopoda – Centipedes
15 or more trunk segments; single pair of legs; last
pair used for sensory info
Most are predaceous
Adaptations include poison claws (maxillipeds) which
spew venom. Most
Reproduction occurs via spermatophores involving
courtship displays; similar to millipedes.
Insect Diversity
Class Pauropoda and Symphyla
Pauropods have a soft body and thin
They have 11 segments and live in leaf litter
Symphylans have 12 leg-bearing segments, no
eyes, and they resemble centipedes. Most
symphylans feed on detritus, but a few are
vegetable and flower pests.
Class Hexapoda (Insecta)
Three Tagmata
Class Hexapoda (Insecta)
External Structure and Locomotion
• The thorax is divided into the prothorax, mesothorax,
and metathorax.
• Legs are attached to each thoracic segment; wings, if
present, are attached to the thorax.
• Spiracles are located on both the thorax and
• The abdomen has reproductive structures for
copulation and oviposition.
Class Hexapoda (Insecta)
Insect Flight
• Insect flight required wings, but the original function of
wings may have been to protect the spiracles.
• Early insects may have been gliders rather than wing
• Flight required the ability to thermoregulate because the
body must be kept warm to allow flight muscles to
contract. Insect flight may be accomplished by direct or
indirect flight mechanisms
• Insects use a direct or synchronous flight
Class Hexapoda (Insecta)
• Direct –
move wings
• Indirect –
shape of
Class Hexapoda (Insecta)
Insect Locomotion
• Insect locomotion includes walking,
running, jumping, or swimming, in addition
to flight. When walking, insects have 3 or
more legs on the ground at the same time.
• Jumping insects have larger metathoracic
legs; some (Fleas) use muscles to “cock”
legs, storing elastic energy
Class Hexapoda (Insecta)
Nutrition and Digestive System
• Insects feed on a diverse array of food
items by biting, piercing, sucking, sponging,
or chewing; their mouthparts are similarly
• The digestive tract consists of a foregut, a
midgut for digestion and absorption, and a
long straight hindgut that may include a
crop and gizzard.
Class Hexapoda (Insecta)
Excretory System
• Malpighian tubules and the rectum
accomplish excretion and resorb water.
• Excretion of uric acid is advantageous for
terrestrial life because of water
conservation, however it is energetically
costly to produce uric acid as the primary
metabolic waste.
Class Hexapoda (Insecta)
Gas exchange
• Gas exchange occurs through the tracheae that
form a finely branching network that pipes air
directly to cells.
• Ventilation is usually aided by muscle contraction
to exchange air in the tracheae.
• Aquatic insects may rely on tracheae, gills, or
Class Hexapoda (Insecta)
Circulatory and Temperature Regulation
• Circulation is accomplished by the blood, which
carries dissolved materials, but is not important in
transfer of gases.
• Thermoregulation is critical for flying insects; they
produce a variable body temperature (heterothermy)
via basking or shivering thermogenesis.
• Honeybees may even cool their hives by beating their
wings at the hive entrance in order to draw cooler,
outside air into the hive.
Class Hexapoda (Insecta)
Nervous Systems
• The nervous system of insects is similar to that of
annelids and other arthropods.
• The supraesophageal ganglion controls sensory
structures of the head, and the subesophageal
ganglion controls the mouthparts and excitatory
functions of other body parts.
• A well developed visceral nervous system also is
present. Insects are capable of some learning and
possess a memory for visual and olfactory cues.
Class Hexapoda (Insecta)
Sensory Functions
• Insect sensory systems include receptors for touch,
vibration, stretching, and chemicals.
• Tympanic organs are found in orthopterans and some
lepidopterans and function in sound reception.
• Compound eyes are well developed in most adult
insects, and are composed of ommatidia. The eye of
an insect functions primarily in detecting movement,
and can also see light waves that humans cannot;
some can even detect polarized light for navigation.
Class Hexapoda (Insecta)
Sensory Function
• Receptors for odor, mechanoreceptors, and stretch
receptors are all relatively well developed—
Johnson’s organs and tympanal organs sense
pressure waves for hearing.
• Chemoreceptors are abundant throughout the
surface of the organism.
• Pheromones are released by insects and function in
intraspecific signaling.
Class Hexapoda (Insecta)
Reproduction and Development
• The most primitive insects, such as silverfish, have
indirect sperm transfer via a spermatophore. They
develop via ametabolous metamorphosis in which the
young are miniatures of the adult, and simply grow in
size through stages called instars.
• Some of the relatively primitive insects have
hemimetabolous metamorphosis where the eggs
hatch to form a nymph that goes through a species
specific number of molts to gradually become an
adult. Adults have wings and sex organs. In primitive
aquatic insects, the larvae are called naiads and often
have gills. Examples include grasshoppers, chinch
bugs, dragonflies, and damselflies.
Class Hexapoda (Insecta)
Reproduction and Development
• The third type of development is called
holometabolous metamorphosis. Immatures
are called larvae (caterpillars of moths and
beetles). Larvae have a species specific
number of molts and the final molt results in
formation of a pupae. A protective case called
a cocoon, a chrysalis, or a puparium may
enclose and protect the pupae. During the
term of pupation, all of the adult characteristics
of the particular species develop. The adult
insect emerges from the protective case in a
process called eclosion.
Class Hexapoda (Insecta)
Reproduction and Development
• Most insects have direct fertilization. Males
often have abdominal, copulatory appendages,
and females may lay eggs using an ovipositor.
Use of pheromones and/or sounds to attract
mates is common, and mating display
behaviors are often well developed and
complex. Timing of reproduction may depend
upon nutrition (female mosquitoes must take
blood meals), day-length, temperature, and
density factors.
Class Hexapoda (Insecta)
Innate Behavior and Social Insects
• Insects have many innate (non-learned) complex
behaviors. The social insects (order Hymenoptera;
the bees, ants and wasps and order Isoptera; the
termites) show the most complex behaviors.
• Several different castes compose the colony.
• Reproductive females are the queens; sterile females
are workers; males (who develop from unfertilized
eggs) are drones (exception: males which are infertile
in the termite colony are also workers). Pheromones
released by the queen control the castes.