1. Insect Diversity
Subphylum Uniramia is an enormous group of mostly terrestrial arthropods that have chewing mouthparts called mandibles (jaws).
Uniramians consist of three classes: Insecta (insects), Diplopoda (millipedes), and Chilopoda (centipedes).
Insects are the largest group of organisms on Earth, with more than 700,000 named species.

2. Orders of Insects Order Examples Number of species Coleoptera
“shield winged”
Beetles,
Weevils
350,000
Diptera
“two winged”
Flies,
Mosquitoes
120,000
Lepidoptera “scale winged”
Butterflies,
Moths
Hymenoptera
“membrane winged”
Ants,
Wasps,
Bees
100,000

3. Insects
Insects are primarily a terrestrial group, and aquatic insects probably had terrestrial ancestors.
Although the great majority of insects are small, others are much larger.
Generally, the larger insects live in tropical areas.
Despite great variation in their size, all insects share the same general body plan, made up of three body sections.

4. Insect Body Plan
Head
Located on an insect’s head are mandibles, specialized mouthparts, and one pair of antennae.
The mandibles and mouthparts of different insect species are adapted for eating different foods.
An insect’s head usually has a relatively large pair of compound eyes and a pair of antennae.
Like the mouthparts, antennae vary greatly in size and shape.

5. Insect Body Plan Thorax
The thorax is composed of three fused segments.
Attached to the thorax are three pairs of jointed walking legs.
Some insects, such as fleas, lice, and silverfish, lack wings, but other adult insets have one or two pairs attached to the thorax.

6. Insect Body Plan Abdomen The abdomen is composed of 9 to 11 segments.
In adult insects, there are no wings or legs attached to the abdomen.

7. Insect Life Cycle
The life cycles of most insects are complex, and often several molts are required before the adult stage is reached.
During the last molt, the young insect undergoes a dramatic physical change called metamorphosis.

8. Complete Metamorphosis
Almost all insect species undergo “complete” metamorphosis.
The wingless, wormlike larva encloses itself within a protective capsule called a chrysalis.
Here, it passes through a pupa stage, in which it changes into an adult.

9. Incomplete Metamorphosis
A smaller member of species develop into adults in a much less dramatic incomplete metamorphosis.
In these species, the egg hatches into a juvenile, or nymph, that looks like a small, wingless adult.
After several molts, the nymph develops into an adult.

10. Flight Insects were the first animals to have wings.
For more than 100 million years, until flying reptiles appeared, insects were the only flying organisms.
Flying insects were able to reach previously inaccessible food sources and to escape quickly from danger.
Basic motion of the insect wing in insect with an indirect flight mechanism scheme of dorsoventral cut through a thorax segment with a wings b joints c dorsoventral muscles d longitudinal muscles

11. Flight
An insect’s wings develop from saclike outgrowths of the body wall of the thorax.
The wings of adult insects are composed entirely of chitin, strengthened by a network of tubes called veins (which carry air and a bloodlike substance).
In most insects, the power stroke of the wing during flight is downward, and it is produced by strong flight muscles.
When at rest, most insects fold their wings over their abdomen, but a few insects are unable to do this.
Most insects have two pairs of wings.
A few groups of insects, such as fleas and lice, are wingless.

12. Flight
In most insects only one pair of wings is functional for flight.
In some species, the second pair of wings serves another purpose.
In grasshoppers and beetles, the forewings act as protective wing covers.
In flies, the hindwings are modified into knoblike structures that help control stability during flight.

13. Social Insects
Two orders of insects, Hymenoptera (ants, bees, and wasps) and Isoptera (termites), have elaborate social systems.
These insects often live in highly organized societies of genetically related individuals.
Within these insect societies, there is a marked division of labor, with different kinds of individuals performing specific functions.
The role played by an individual in a colony is called its caste.
Caste is determined by a combination of heredity, diet (especially as a larva), hormones, and pheromones (chemical substances used for communication).

14. Insect Relatives Centipedes and Millipedes have similar bodies.
Each has a head region followed by numerous similar segments.
Each segment bears one or two pairs of legs.
Centipedes have one pair of legs per segment and can have up to 173 segments.
Modern millipede segments have two pairs of legs.
While centipedes are carnivores, most millipedes are herbivores.

15. Comparison of Crustaceans and Insects
Characteristic
Crustaceans
Insects
Nature of Appendages
Most are branched at the end
Unbranched at the end
Antennae
Two pairs
One pair
Chewing Appendages
Usually three pairs
Location of Appendages
Cephalothorax and Abdomen
Head and Thorax
Respiration
Gills
Tracheal System

16. Subphylum Trilobitomorpha
NB #111
Lived from 600 MYA to 345 MYA
Dominant life form while they lived
Fed on annelids, molluscs, and detritis (decaying organic matter)
Body flat and divided into three segments:
Head, thorax, and pygidium
Could roll into a ball for protection (kind of like an arthropod of today)
Branched appendages possibly used for walking, digging, or swimming

17. Subphylum Crustacea Includes crayfish, shrimp, lobsters, and crabs
All aquatic….
Except some isopods and crabs
Differences from other arthropods..
2 pairs of antennae (other arthropods have 1)
Biramous appendages
Segments with two rami (structure that gives appendage a Y shape)

18. Subphylum Crustacea Class Malacostraca
Largest class of crustaceans
Crabs, lobsters, crayfish, shrimp, mysids, shrimplike krill, isopods, and amphipods

19. Subphylum Crustacea Class Malacostraca
Crayfish:
General crustacean characteristics
Two body regions:
Cephalothorax
Fused head and thorax
Abdomen
Posterior
Locomotor and visceral functions
Form of a muscular tail

20. Subphylum Crustacea Class Malacostraca
Crayfish:
Paired appendages present in both body regions
Two pairs of antennae
3rd-5th pairs associated with the mouth
3rd pair modified into mandible
Chews and grinds food
4th & 5th pairs called maxillae
Food handling
6th – 8th- maxillipeds- handle food
9th-13th- pereopods- walking legs
1st pereopod is a cheliped (large pincher)

21. Subphylum Crustacea Class Malacostraca
Crayfish:
Diet- other invertebrates, plant matter, and dead or dying organisms
Large stomach specialized for grinding (foregut)
Digestive gland secretes digestive enzymes to break down food
Gills- located in chambers
Sensory structures:
Compound eyes, simple eyes, statocysts, chemoreceptors, proprioceptors, and tactile setae

22. Subphylum Crustacea Class Malacostraca
Crayfish:
Excretion:
Green glands or antennal glands (actually green in color)
Reproduction:
Dioecious
Mate after female has molted
Male flips the female on her back
Fertilzation occurs after copulation
Sperm deposited on female
Eggs are sticky and secure to the female’s pleopods

23. Subphylum Crustacea Class Branchiopoda
Primarily live in freshwater
Fairy shrimp and brine shrimp
Flattened, leaflike appendages used in…
Respiration
Filter feeding
Locomotion

24. Subphylum Crustacea Class Maxillopoda
Short bodies and a unique combination of 5 head, 6 thoracic, and 4 abdominal segments, plus a telson
Copepods- abundant (vector for Guinea worm)
Barnacles- sessile & may colonize on ships
Mostly marine
Copepod
Barnacles

26. Subphylum Chelicerata
Spiders, mites, ticks, horseshoe crabs, and sea spiders
Two tagmata
Prosoma (cephalothorax)
Sensory
Feeding
Locomotion
Opisthosoma
Digestion
Reproduction
Excretion
Respiratory organs