INSECTS OF TEXASJohn A. Jackman
Insects Dominant Land
• Most abundant land animals
• More species
• More numbers
• Weigh more than all
other land animals combined
Insect Diversity
Location Approximate
Number of Insects
World 3,000,000
USA 300,000
Texas 30,000
Insect Diversity
• Insects make up about 70% of all living species
• Most insects are harmless and indeed, many are valuable to humans in a number of ways
How Many are Pests?Less than 5% of all insects
are described as pests
Insects Are Pests When They
• Feed on vegetables and flowers
• Destroy structural wood
• Transmit disease
• Bite and sting
• Become a nuisance
Good Things That Insects Do
• Pollinators
• Decomposers
• Commercial Products
• Biological Control
Aquatic Insects
• About 5% of insects are aquatic
• Includes mayflies, dragonflies,
damselflies, stoneflies, and caddisflies
• Other groups like flies and beetles have
many aquatic forms
• No insects live in the oceans
Metamorphosis: change in
form during growth
• Grubs become beetles
• Caterpillars become moths or butterflies
• Maggots become flies
Insect Characteristics
• Hard exoskeleton
• Cold blooded
• Three body regions
• Six legs (usually)
• Many forms have wings
Exoskeleton
The Head
• Several segments fused together
• Occipital foramen
• Structures on insect head include
– Antennae and mouthparts
– Compound eyes and ocelli
The Thorax - Legs
• Three pairs of legs
• Each leg is subdivided
into 6 parts
– Coxa, trochanter, femur,
tibia, tarsus, pretarsus
• Variations in leg structure
– Good indications of habits
– Useful characters in
identification
The Thorax - Wings
• Attached to body wall on 2nd & 3rd thoracic segments
• Flattened and flap-like
• Strengthened internally
• Variations in wing structure
• In a few insect groups, wings are only present in certain individuals
Muscular System
• Several hundred to over 2,000 muscles
• Composed of striated muscle cells
• Attached to the inside of the exoskeleton
Digestion & Excretion
• Digestion as a process
• Alimentary canal
– Foregut, midgut, hindgut
• Glands associated with
digestive system
• Malpighian tubules
Foregut
Midgut
Hindgut
Circulatory System
Respiratory System
• In insects, oxygen and carbon dioxide transport is carried out by the tracheal system