Insects Chapter 37

The Insect World Section 37.1

Characteristics of Insects Three tagmata: Head: mandibles to chew, pair of antennae for sensory Thorax: 3 pairs of jointed legs, most have 1 or 2 pairs of wings Abdomen: 9-11 segments

Head Thorax Abdomen

Exoskeleton with… Antennae Examples: Leg Examples:

Appendage examples:

Two types of mouthparts: Sucking Chewing

Entomology: The study of insects Person = entomologist & other terrestrial arthropods Person = entomologist Classify insects into 25 orders based up: Mouthparts Number of wings Type of development

Classification of Insects Subphylum: Hexapoda Class: Insecta Common Orders: Hemiptera Homoptera Isoptera Odonata Orthoptera Coleoptera Diptera Hymenoptera Lepidoptera Table on page 743

Success of Insects Insects live everywhere (except deep ocean) 1 million species (more than 3x all other animals!) 10 million might exist Why so many? Ability to fly Escape & dispersal Small Short life spans Quick adaptations

Insects and People Competition for food  Spread diseases  Plague, typhoid fever, malaria Consume clothing & carpet  Crop pollination  Make commercial products  Wax, silk, honey Recycle nutrients  Video

Insect Development Hatchling must go through several molts to reach adulthood (sexual maturity) Metamorphosis: major developmental changes from larvae to adult Two forms: incomplete & complete

Incomplete Metamorphosis Nymph: immature form of insect that looks like adult Only the adult can fly and is sexually mature

Complete Metamorphosis Two stages of development that look drastically different Pupa: changing from larvae to adult Cocoon: protective covering of pupa Chrysalis: butterfly pupa protection

Insect Defense Passive defense examples: Aggressive defense examples: Camouflage Look like plants Aggressive defense examples: Venomous stingers Harmful chemicals Warning coloration: color pattern to warn of poison

Mimicry Mullerian mimicry: poisonous species mimics the coloration of another poisonous species Bees & wasps Batesian mimicry: harmless species mimics the coloration of a poisonous species Monarch & viceroy butterflies

Grasshoppers Subphylum Hexapoda

External Structures: Head = mouthparts, antennae, simple & compound eyes Thorax = 3 parts: Prothorax = 1st pair walking legs Mesothorax = 2nd pair walking legs & forewings (protective) Metathorax = 3rd pair legs (jumping) & hindwings (flying)

Abdomen = upper & lower plates connected by flexible exoskeleton Covered by waxy cuticle (prevents desiccation)

Video Feeding Chewing mouthparts (feed on plants) Labrum: functions like upper lip Labium: functions like lower lip Mandible: tears food Maxilla: helps hold & cut food Video

Digestive Tract Mouth  saliva (from salivary glands)  esophagus  crop (storage)  gizzard  midgut/stomach (bathed in enzymes from gastic ceca)  nutrients absorbed in hindgut/intestine  anus

Circulation, Respiration, & Excretion Circulatory system: Open Aorta (large, dorsal vessel) Heart (pumping organ) Respiratory system: Tracheae (site of air diffusion inside body) Spiracles (openings to allow air in/out) Excretory system: Malpighian tubules: return most water back to hemolymph, rest leaves body via feces

Neural Control CNS = brain, ventral nerve cord, & ganglia at each segment Antennae – touch & smell 3 simple eyes – intensity of light 2 compound eyes – sight Tympanum – sound & communication Sensory hairs - touch

Reproduction Separate sexes (male & female) Sexual Reproduction: male deposits sperm into female seminal receptacles Eggs released from ovaries Internal fertilization Ovipositor: digs a hole in soil to lay eggs

Insect Behavior Section 37.2

Communication Chemical communication via pheromones Chemical released that affects behavior or development of other members of same species Uses of pheromones: Attract mates Identify hives Food trails video

Communication Con’t… Sound communication via chirping, buzzing, etc. (crickets, mosquitoes) Attract females Protect territories Sight communication via flashes of light (fireflies) Find mates

Behavior in Honeybees Social insects: insects that live in colonies with division of labor Innate behaviors: genetically determined Not taught or learned Three types of honeybees: Worker Drone Queen

Worker Bees Sterile females First adult week: feed honey & pollen to queen, drones, & larvae Royal jelly Next two weeks: secrete wax (build & repair honeycomb), remove wastes, guard hive, circulate air in hive

Continued… Last weeks of life: collect nectar & pollen Adaptations: Barbed stingers for protection of hive Mouthparts for lapping nectar Legs with pollen packers, baskets, & pollen combs

Drones Males developed from unfertilized eggs Parthenogenesis Can travel from hive to hive Sole function: deliver sperm to queen succeed in mating = death penis and associated abdominal tissues are ripped from the body at intercourse

Queen Bee Continuous diet of royal jelly as larvae = queen bee Secretes pheromone “queen factor” that prevents other females developing into queens Sole role: reproduction Mates only once Sperm remains inside her for 5+ years Lays millions of eggs per year! Video

The Dances of the Bees Round Waggle Dancing performed by scout worker bees Round dance: told workers that food was nearby but not exact location Waggle dance: told workers that food was far away and told location Round Waggle

Altruistic Behavior Definition: aiding other individuals at one’s own risk or expense Kin selection: increasing the propagation of one’s own genes by helping closely related individuals reproduce Example: worker bee stinging = death Video