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•6 legs •Uniramous legs •3 tagmata – head, thorax, abdomen •Appendages •Appendages on head & thorax •Abdominal appendages greatly reduced or absent Class Entognatha Bases of mouthparts enclosed within head capsule Ametabolous Lack wings Order Collembola Order Diplura Order Protura Class Insecta Bases of mouthparts visible outside the head capsule Blattodea Coleoptera Dermaptera Diptera Embiddina Ephemeroptera Hemiptera Hymenoptera Isoptera Lepidoptera Mantodea Mantophasmatodea Neuroptera Odonata Orthoptera Siphonaptera > 1 million insect species Entomology- study of insects Habitat Mainly terrestrial: soils, forest, plants, deserts, wastelands, mountaintops, other organisms Fresh water Few marine: Brackish water, salt marshes, sandy beaches Wide Distribution due to flight and high adaptability Adaptability can be seen in wide diversity Adaptability Cuticular exoskeleton Epicuticle has waxy and varnish layer to close spiracles Extract maximal fluid from food and fecal matireals Retain water produced in cellular respiration (oxidative metabolism) Diapause- resting stage when insects may lie dormant during inhospitable conditions Tagmata: head, thorax, abdomen Cuticle composed of: Sclerites (4 plates) Dorsal Tergum Ventral Sternum Pair of lateral pleura (abdominal pleura membraneous) Tergum Sternum Ovipositor Thorax Prothorax Pair of legs Tagmata: head, thorax, abdomen Head Pair compound eyes, pair of antennae, 3 ocelli Moutparts: labrum, pair o mandibles, pair o maxillae, labium, tonguelike hypopharynx Mesothorax Pair of legs Pair of wings (in most) Metathorax Pair of legs Pair of wings (in most) Legs modified for special purposes Terrestrial: walking legs with terminal pads and claws Pads may be sticky (why?) Grasshopper hindlegs: adapted for jumping Mole crickets: first pair of legs for burrowing Aquatic: paddle-shaped appendages for swimming (i.e. waterbugs) Mantis forelegs: long and strong for grasping prey Double membrane with veins of thicker cuticle What do you think the purpose of these veins are? Are insect wings homologous or analogous to bird and flying mammal wings? Most have two pairs flies only have one pair, second pair being halteres Halteres- balancers Flies: thin & membraneous Beetle forewings: thick & stiff Grasshopper forewings: partchment-like Butterflies/moths: covered in fine scales Caddisflies: covered with hairs Digestive System Circulatory System Respiratory System Excretory System Nervous System Reproductive System Foregut- lined with cuticle Mouth with salivary glands Esophagus Crop for storage Proventriculus for grinding Midgut Stomach Gastric ceca Hindgut- lined with cuticle Intestines Rectum Anus Phytophagous- feeding on plant juices/tissues Some can eat any plant, some are plant-specific Some ants/termites cultivate fungus gardens Mutualistic symbiotic relationship (how is this so?) Saprophagous – feeding on dead animals Many beetles & larvae Predaceous- feeding on other insects & animals Parasitism Fleas- scavengers as larvae, parasites as adults Lice- parasitic throughout life cycle Hyperparasitism……parisitoid Wasp larvae Feeding habits determined by highly specialized mouthparts Biting/chewing mouthparts Mandibles strong with toothed plates to bite/tear food while maxillae holds food to mouth Enzymes secreted by salivary glands add chemical action ot the chewing parts Sucking mouthparts House flies & fruit flies- no mandibles; labium = 2 soft lobes with small tubules for capillary action Horse flies- slender, tapering mandibles to bit and then to suck blood Mosquitos- piercing with stylets and sucking through food channel Honey bees- labium= flexible/contractile “tongue” covered with many hairs for capillary action and pumping pharynx Butterflies/moths- no mandibles; maxillae = proboscis Proboscis coiled while not feeding; extends during feeding while pharyngeal muscles pump fluid Tubular heart in pericardial cavity Dorsal aorta Hemolymph (blood) Accessory pulsatory organs move blood to legs/wings Body movements move blood Consists of plasma and amebocytes Function: distribute substances throughout body (i.e. molting hormones and nutrients) Tracheal system- tubes that pipe oxygen directly to each cell Function: rapid oxygen-carbon dioxie exchange and restrict water loss Abdominal muscles provide pumping action that draws air in/out Spiracles Paired in thorax; 7/8 pairs in abdomen Primitive hole in integument or with valve/closing mechanism Why would this mechanism be a good adaptation? Tracheae Lined with cuticle, shed during molts Taenidia Spiral thickenings of the cuticle Support tracheae & prevent collapse Tracheoles Not lined with cuticle Fine, fluid-filled tubules that tracheae branch into Very small insects Gas exchange through diffusion along concentration gradient Water insects i.e. nymphs, larvae, adults Gas exchange through diffusion through body wall into and out of tracheal network just under integument Aquatic nymphs of stoneflies & mayflies- tracheal gillsthin extensions of body wall containing rich tracheal supply Dragonfly nymphs- rectal gills- ridges in the rectum where gas exchange occurs as water enters/leaves Malpighian tubules- excretory organs & body fluid conservation Environment dependent Arid dwelling insects Reabsorb nearly all water from rectum = nearly dry mixture of urine & feces Leaf-feeding insects Take in & excrete large amounts of water Freshwater larvae Need to excrete water and conserve salts Dry grain-feeding insects Conserve water and excrete salts Brain = fusion of ganglia Some insects have giant fiber system Visceral nervous system (similar to autonomic nervous system of vertebrates) Various sense organs Sense organs detect mechanical, auditory, chemical, visual, and other stimuli Can sense temperature, humidity, body position (proprioception), gravity, etc… All over body, especially on appendages Visual = photoreceptors Ocelli = located on head Dermal light receptors = located on body Compound eyes = large and composed of ommatidia Flicker-fusion tests Auditory Sensilla = sensitive hair-like structures that can detect sounds Modification of cuticular surface for sensory stimuli reception with one or more neurons Tympanis organs = structures sensitive to sonic/ultrasonic sound Sensory cells attached to thin tympanic membrane that encloses air space in which vibrations can be detected Chemoreceptive sensilla Found on antennae, mouthparts, and legs Mechanical stimuli i.e. contact pressure, vibrations, tension changes in cuticle Detected by sensilla or sensory cells in the epidermis Neurosecretory cells located in brain have endocrine function that plays a role in molting and metamorphosis Pheremones = chemicals used to attract a mate Dioecious Can attract mate through pheromones (even those several miles away), flashes of light, sound signals, color signals, courtship behavior Usually internal fertilization Sperm deposited into female at time of copulation Spermatophores being transferred to female Sperm can be stored in seminal receptacle for later fertilization # of eggs Queen honey bee may lay >1 million eggs in a lifetime Some flies = ovoviviparous = one offspring at a time Insects with short life cycles and no offspring care = lots o’ eggs Eggs laid in particular habitat to which they are cued to by visual, chemical, or other clues Random facts o’ interest Butterflies/moths lay eggs on type of plant caterpillar feed on Tiger moth = pigweed Sphinx moth = tomato plant Monarch butterfly = milkweed Terrestrial insects w/ aquatic immature instars lay eggs in water Braconid wasp lay eggs in sphinx moth caterpillar where offspring will feed and pupate in white cocoons Ichneumon wasps deposits eggs in larva for her offspring to be parasites Uses long ovipositors to penetrate wood to find larva of wood wasp or wood-boring beetle Beneficial insects Harmful insects Control of insects