Why Study Terrestrial Arthropods?1. Apods more species richness than any

other phylum ( hyper diverse)

2. Apods consistent up to 80% of all animal life

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.

Pollination

• Insect pollinators are responsible for 1/3 of food in the grocery store.

Pollination• 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 overgrowth

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 venoms1. 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 services1. Processes of decomposition

2. Nutrient cycle

3. Pollinators

4. Bio Control – use natural predators or parasites to control pests.

5. Important to the health of terrestrial ecosystems

2. Nutrition yum!1. http://www.life.uiuc.edu/ib/109/Lab/Edible%20Insects/edible%20insect

%20lab%20photos.html

Impacts on human welfare

Positive Impacts3. Intrinsic molecules

1. Silks2. Venoms3. 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

basis• 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

4. 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 DiplopodaClass ChilopodaClass PauropodaClass SymphylaClass 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 exoskeleton

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 abdomen.

• 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 flappers.

• 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 –

muscle contractions move wings

• Indirect – muscles change shape of thorax

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 diversified.

• 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 diffusion.

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.