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Entomology Biol 405/405L Holly Downing, PhD LSB 111 Introduction • Handout – Course expectations • Collection methods – Supplies distributed Charles Darwin inspecting collected during the voyage of the Beagle. (After various sources, especially Huxley & Kettlewell 1965 and Futuyma 1986.) What is an insect? • Animal Classification – – – – – – – – Domain Kingdom Phylum Class Order Family Genus Species Eukarya Animalia Arthropoda Insecta Hymenoptera Vespidae Mischocyttarus drewsenii Kingdom Animalia Invertebrates • 95% of Animal Kingdom • Multicellular, eukaryotes • Sponges – most primitive – Cells, but no organized tissues • Jellyfish – 2 tissue layers • Other invertebrates and vertebrates have 3 tissue layers • Coelom – body cavity – Arthropoda one of several phyla Vertebrates • 5% or less Animal Kingdom • Includes animals with vertebral column – Some Chordata are considered Invertebrates Phylum Arthropoda • Invertebrate animals with jointed legs • Exoskeleton made of chitin • Molt exoskeleton as grow • Active due to jointed legs • All types of habitats • Very successful group Figure 1.1 Speciescape, in which the size of individual organisms is approximately proportional to the number of described species in the higher taxon that it represents. (After Wheeler 1990.) Entomology • Entomologists study insects – – – – – Anatomy and Physiology Ecology Evolution Behavior Diversity, species richness – Genetics – Biochemistry • Insects make excellent research models – Easy to rear – Short generation time – Simpler anatomy, neurophysiology – Very diverse, in all but under water ocean habitats – Simple to complex behavior Importance of Insects A mature larva of the palm weevil, Rhynchophorus phoenicis (Coleoptera: Curculionidae), a traditional food item in central Angola, Africa. (Larva after Santos Oliveira et al. 1976.) • Research • Food – nonhumans, too • Products such as honey, dyes, shellac • Work such as pollinators, predators • Competitors for crops and spread diseases • Spread diseases in humans, livestock and pets Ecosystem function • Nutrient recycling • Plant propagation • Maintenance of plant community balance • Important source of food for other animals (and some carnivorous plants) • Maintenance of animal community structure Where are insects found? • Antarctic: 2 spp of fly – Bird fleas, lice – Seal lice • Arctic: 300 spp. Mostly flies • Himalayan mts: 1920,000 ft. elevation there are permanent residents • In air: most spp can fly • Deep caves, hot springs, salt lakes, pools of petroleum • 3% freshwater spp • 0.1% intertidal zone – One water strider lives on surface of open ocean – None in deeper water of ocean Why So Diverse and Successful? • Why not in oceans? – Entered terrestrial habitat before other types of organisms – Arthropod body already had exoskeleton and jointed legs that would support movement on shore • Also, protects from desiccation • Internal fertilization • Chorion protects egg Ocean niches filled with Crustaceans, another successful Arthropod group Why So Successful? • Entered terrestrial habitat • Flight before vertebrates – Avoid predation (before • Small size there were birds) – Short generation time – Great reproductive capacity as a result – High fertility – Population explosions can overwhelm predators – Natural selection can work quickly – Easily dispersed on wind – Can travel farther, faster – < 1% are flightless • Holometabolous – Most successful groups – Ability to use multiple niches – Ex. Flies: maggot in garbage or dung; adult is free flying Why So Successful? (Con’t) • Social Behavior – Animal biomass in tropical rainforests: • Insects = 50% • Social insects = 80% of insect biomass! – Cooperative defense & brood care – Increased foraging efficiency – Can utilize resources that single individuals can’t access Evolution of Insects • Onychophora – velvet worms – Probably similar to first arthropods – About 80 spp today – 1.5-15 cm long – Moist, tropical areas – Similar to fossils from Cambrian (500 mya) – Segmented with appendages on each segment -- Cuticle; molts as grows -- Chitin in jaws and leg claws -- Open circulatory system -- Tracheal respiratory system Evolution of Insects (con’t) • Body plan: consolidation of segments – Head, thorax, abdomen – Head : 6 segments • Appendages became mouthparts & antennae • Segment ganglia became enlarged to form brain • Segments fused 1 – labrum (pre-oral) 2 – antenna 3 – lost (brain section there) 4 – mandibles 5 – maxillae 6 - labium Mouthparts also have sensory palps So head = centralized neural processing, sensory input, and food intake Evolution of Insects (con’t) • Thorax: 3 segments – Legs (3 pr) & wings (2 pr) – Strong muscles that attach to infoldings of exoskeleton • Abdomen: 11 segments – Lost most appendages – Some modified for penis or ovipositor • This is basic plan, but there’s a lot of diversity Insect Conservation • Umbrella effect of flagship species – Flagship rarely insects – But they can benefit • Some exceptions – Butterfly and moths • Monarch butterflies • El Segundo blue of LA sand dunes • Queen Alexandra’s birdwing Other showy species such as beetles and dragonflies or economically important species such as bees can be flagship species as well. Insect Conservation (con’t) • Habitat conservation – Many species protected – Species interactions are important – Need to know about the often complex ecology and interrelationships among species for this approach to be successful • Keystone species are those that have a large influence on an ecosystem and the communities of species – Usually think of this as a vertebrate or plant spp – But some insects can have major impacts • Termites, bees, ants Box 1.1 Example of complex habitat requirements – Large Blue and ant host in southern England