Characteristics of Arthropods

Arthropoda Characteristics

• Arthropods have an exoskeleton made of chitin
• Their bodies are segmented
• They have segmented appendages
• They exhibit bilateral symmetry
• They have a dorsal tubular heart
• Their nerve chord is ventral and paired

Classes of Arthropods

• Arachnida: Spiders, mites, ticks, scorpions
• Diplopoda: Millipedes
• Chilopoda: Centipedes
• Insecta: Insects

Arachnida Characteristics

• Arachnids have bodies divided into two parts
• They have four pairs of legs
• They lack antennae
• They lack wings

Chilopoda (Centipedes)

• Centipedes have longer antennae than millipedes
• They are flattened in cross-section
• Each segment has one pair of legs
• They are beneficial predators, preying on other arthropods
• They move quickly
• They have poison glands and can inflict painful bites

Diplopoda (Millipedes)

• Millipedes feed on fungi and decaying plants
• They can damage plants
• They have two pairs of legs per segment
• Their bodies are divided into two parts (head and body)
• They are round in cross-section
• They move slowly

Insect Identification

• Insects are a subclass of arthropods that can be identified from the image provided.

Cuticle

• Insect exoskeletons are formed from epithelial cell layers that produce chitin, proteins, fats, and pigments
• The cuticle has layers, including the epicuticle, exocuticle, and endocuticle

Insect Head Parts

• Genae (Cheeks): The sides of the insect head
• Compound Eyes: Multi-faceted eyes
• Ocelli (Simple Eyes): Smaller, simpler eyes
• Antennae: Sensory appendages
• Clypeus: Part of the head, located below the frons
• Frons: The front of the head
• Mouth: The structures for feeding
• Labrum: Upper lip
• Mandibles: Jaw-like structures
• Maxillae: Parts of the mouth
• Labium: Lower lip

Types of Mouthparts

• Chewing: Grasshoppers have chewing mouthparts
• Piercing-Sucking: Mosquitoes have piercing-sucking mouthparts
• Sponging: House flies have sponging mouthparts
• Siphoning: Butterflies have siphoning mouthparts
• Chewing-Lapping: Honeybees have chewing-lapping mouthparts

Orientation of the Head

• Prognathous: Mouthparts point forward
• Hypognathous: Mouthparts point downward
• Opisthognathous: Mouthparts point backward

Types of Antennae

• Setaceous: Bristle-like (e.g., Dragonflies)
• Filiform: Thread-like (e.g., Cockroaches, Ground Beetles)
• Moniliform: Bead-like (e.g., Termites)
• Serrate: Saw-toothed (e.g., Click beetles)
• Clavate: Gradually clubbed (e.g., Carrying beetles)
• Capitate: Abruptly clubbed (e.g., Butterflies)
• Pectinate: Comb-like (e.g., Male Glow-worms)
• Geniculate: Elbowed (e.g., Ants, Weevils)
• Lamellate: Nested plates (e.g., Scarab Beetles, June Bugs)
• Pulmose: Feather-like (e.g., Mosquitoes, Male Moths)
• Aristate: Pouch-like with lateral bristles (e.g., Flies)

Antennal Structure

• Antennae consist of scape, pedicel, and flagellum

Why Insects are Successful

• Hard and light exoskeletons
• Small body size
• Ability to fly
• Short life cycles and rapid reproduction