insects of texas - texas master...

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