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PHYLUM ARTHROPODA SUBPHYLUM UNIRAMIA/HEXAPODA CH. 21 • Outnumber any other species of animals • Adapted to all climates/all land environments • 200 million insects per every human being • 2 classes in subphylum: Insecta and Entognatha • Entomology- study of insects • Extensive group that provides ecological, medical and economic significance BODY PLAN • Six legs • Uniramous legs (not biramous) • Three tagmata (fusion of segments) • Head, Thorax, and abdomen • Cuticle is made of Four plates • Exoskeleton is made of a complex system of plates • Sclerites Exoskeleton is rigid due to schleroproteins and not due to chiton • Pair of large compound eyes, three ocelli • 1 set of antennae • Mouthparts: Mandible and Maxillae • Each section of thorax has a pair of legs • Legs are modified for special purposes • Many variations among beetles FLIGHT • Only invertebrates that can fly • Wings are not homologous to mammal wings and bird wings • Homologous? - means from a common ancestor • Many variations among wing patterns and development • EX: some are wingless (silverfish) • Female ants lose wings after nuptial flight • Termite workers are wingless • Wing movement may be direct (attached to wing) or indirect (not attached to the wing) • Flight muscle contraction can have two basic types of neural control: • 1) synchronous –single nerve impulse & one wing stroke • 2) asynchronous –complex action depending upon energy storage ; not inline with nerve impulses NUTRITION • Varies depending on species • Digestion system includes: foregut, mouth, esophagus, crop, gizzard, midgut, and hindgut • Most insects feed on plant tissues and juices (herbivorous ) • Many are also parasites Few are saprophagous (feed on dead animals) Some are truly evil and kill their hosts like many wasps( in movie) OTHER SYSTEMS • Respiratory S.- tracheal tubes , spiracles that lead to the outside • Trachea branch out into smaller tubes called tracheoles • Some have air sacs • Aquatic insects have tracheal gills OTHER SYSTEMS • Excretory : Malpighian tubules – operate with specialized glands in wall of rectum. • Nervous System: fusion of ganglia • Sense Organs: keen sensory perception: mechanical, hearing, chemical( odors), and visual OTHER SYSTEMS • Vision- two types of eyes: simple and compound • Nymphs and Larvae may have simple, • Most adult insects have compound eyes • Reproduction: some can reproduce with just females (parthenogenesis) • Majority of insects reproduce sexually • Demonstrate courtship behaviors: • EX: Pheromones (chemicals given off to excite the opposite sex), flashes of light, sounds, colors • Many eggs are produced (great survivability) METAMORPHOSIS • Changing in form from youth to adult stages • Incomplete metamorphosis: EX: grasshoppers, cicadas, mantids, dragonflies Young are called nymphs, increase in size through molting Complete metamorphosis: EX: 88% of insects, stages represent many physical processes from youth to adult COMPLETE METAMORPHOSIS • 1) Larvae- young: ex: caterpillars, maggots, grubs • 2) Pupa-transitional stage, inactive, can survive winter • 3) Adult – • Hormones regulate metamorphosis • Insects may also have a period of hibernation or dormancy • Some have a longer period called diapause DEFENSE • • • • Mimicry- impersonating a poisonous insect Camouflage- blending in with environment Repulsive odors (EX: Stinkbug) Bad taste – Monarch butterfly • Intensely Social creatures: cooperation among all • EX: honey bees, ants, termites • Caste system: Queen, workers, drones, soldiers BENEFICIAL VS. HARMFUL • Important for the cross-fertilization of of crops • Bees pollinate 14$ billion worth of crops every year • Coevolution with plants • Other insects destroy harmful ones : • EX: tiger beetles, praying mantids, ladybugs, ant lions HARMFUL • Destroy crops and forests • 10% are parasites: lice, bloodsucking flies, Anopheles mosquito, mosquito (West Nile) • Destroy food, clothing , and property • Use of pesticides, bacteria and viruses, and biocontrol have all been used to rid harmful insects • Using crop rotation, resistant plant varieties have also been used as of late