Biology: Centipedes and Millipedes

Centipedes and Millipedes

• Centipedes are elongated, segmented creatures with one pair of legs per body segment.
• All centipedes are venomous and can inflict painful stings.
• Centipedes belong to the kingdom Animalia, subkingdom Metazoa, phylum Arthropoda, and class Chilopoda.
• Millipedes have two pairs of jointed legs on most body segments.
• Most millipedes have elongated, cylindrical or flattened bodies with more than 20 segments.
• Millipedes are generally harmless to humans, although some can become household or garden pests.

Insects (Class Insecta)

• Insects have all the characteristics of Arthropods and three body regions: head, thorax, and abdomen.
• Insects also have three pairs of legs, one pair of antennae, and bilateral symmetry.
• Insects belong to the class Insecta, which is distinct from other classes of Arthropods like Diplopoda (millipedes) and Chilopoda (centipedes).

Arthropod Characteristics

• All Arthropods have a chitinous exoskeleton.
• All Arthropods have bilateral symmetry.
• All Arthropods have jointed appendages.
• All Arthropods have segmented bodies.
• All Arthropods have a tubular digestive tract, a dorsal tubular circulatory system, and a ventral nervous system.

Phylum Arthropoda

• The Phylum Arthropoda includes Chelicerata (e.g., scorpions, spiders, ticks) and Mandibulata (e.g., lobsters, insects).
• Chelicerata have mouthparts outside the head, two body regions, no antennae, and four pairs of walking legs.
• Mandibulata include lobsters, which have long bodies with muscular tails, and live in crevices or burrows on the sea floor.

Exoskeleton

• Exoskeleton provides support, allowing for large open spaces.
• Exoskeleton provides muscle attachment points.
• Exoskeleton provides a body covering and good protection.
• Exoskeleton provides water conservation, which is essential for insects.
• Exoskeleton provides growth restrictions, which is a problem.
• Exoskeleton provides good mechanical advantage, enabling insects to perform impressive feats.

Insect Body Regions

• Insect body regions are called Tagma, which are groups of segments that function together to perform a general task.
• Head Tagma: perception, food intake.
• Thorax Tagma: locomotion, food processing.
• Abdomen Tagma: reproduction, excretion.

Insect Head Structures

• Antenna: odor receptors, used for insect identification.
• Compound eyes: composed of many individual eye units called Ommatidia.
• Simple eyes: composed of 1 unit, often arranged in the shape of a triangle on adult insects.