introduction to insect classification of insect general characteristic of arthropoda

1. Introduction & Classification
of
Arthropods

2. Features of All Arthropods
 All have exoskeletons for support and protection
 All have jointed appendages
 Body regions include: a head, thorax, and an
abdomen.
 Some have a cephalothorax (head and thorax
are fused together)
 All arthropods molt (shed exoskeleton)

3. General Characteristics Cont’d
 Arthropods use either gills, tracheal tubes, or book lungs
for gas exchange.
 Acute senses include simple and compound eyes,
brains, and many ganglia.
 Arthropods use pheromones to communicate.
 They have open circulatory systems, complete digestive
system, and efficient means of wastes excretion.
 Arthropods reproduce sexually, but some exhibit
parthenogenesis.

4. Phylum Arthropoda is classified
into four subphylla
 1- Trilobita Extinct (Fossilised )
 2- Crustacia (All aquatic forms )
 3- Chelicerata
 Class Arachnida
 ( includes three important orders)
 (A) Acarina (Ticks and mites)
 (B) Scorpionida (All forms of scorpions)
 (C) Areinida (all spiders)
 4- Uniramia – Three classes-Hexapoda;
Chilopoda; and Diplopoda

5. Class Arachnida
 Spiders, scorpions and mites belong to this class.
 Spiders are the largest group of arachnids.
 Most arachnids have only 2 body regions- a cephalothorax and the
abdomen.

6. Arachnids Cont’d
 Spiders have silk glands for spinning webs and for wrapping their
eggs in a cocoon.
 Ticks and mites have only one body segment.
 Ticks feed on mammalian blood and can expand up to 1 cm.
 Mites are very small and cannot be seen by the naked eye. However
their bites, called chiggers, can be felt.
 Scorpions have many body segments and have a long tail with a
venomous stinger at the end.

7. Class Crustacea
 Most crustaceans are aquatic and use gills for gas exchange.
 2 pairs of antennae for sensing.
 Mandibles for crushing food that move side to side.
 Eyes are located on movable stalks.
 Many have five pairs of walking legs used for seizing prey and
cleaning other appendages.
 First pair is often modified into strong claws.

8. Crustaceans Cont’d
 Crabs, lobsters, shrimp, crayfish, barnacles,
water fleas, and pill bugs are crustaceans.
 Some have three body sections, and others
have only two.
 Land crustaceans like pill bugs must live in
damp environments for efficient gas exchange.

9. Class Chilopoda and Diplopoda
 Centipedes belong to class Chilopoda and millipedes belong to
class Diplopoda.
 Centipedes are carnivorous and eat soil arthropods, snails, slugs,
and worms.
 Centipede bites are painful to humans.
 Both have Malphigian tubes for waste excretion.
 Both have tracheal tubes for gas exchange.
 Millipedes eat mostly plants and dead material.
 Millipedes also have stink glands for scaring predators.

10. Class Merostomata
 Horseshoe crabs belong to this class.
 Have remained unchanged since Cambrian period.
 Have exoskeletons similar to trilobites
 Feed on seaweed, mollusks, and worms on bottom of
oceans.
 Females lay eggs on land.

11. Class Insecta
 Insects are the largest group and most successful arthropods.
 Insects may only mate once or twice in their lifetimes.
 Internal fertilization
 Large number of eggs are produced to ensure a large number of
offspring.
 Females lay eggs in wood or the ground.
 May go through complete or incomplete metamorphosis depending
on species.

12. Insects Cont’d
 Complete metamorphosis: egg, larva, pupa, and adult.
 Incomplete metamorphosis: egg, nymph, and adult.
 Nymphs compete with adults for same resources and
are not sexually mature.