Survey
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Announcements • Insect collections due April 2 – ID to order only • Field trips next two Mondays – FOP – Laguna – Arrive by 8 am for departure and arrival at SSU again by noon – Wear clothes that can get damp Reproductive system • • • • • • Dioecious- female and male Usually reproduce sexually, and both sexes present If asexual reproduction, males absent Internal fertillization Sperm stored in spermatophore Usually eggs laid, some live birth • For now skipping insect sensory structures Female reproductive system • Eggs made in ovaries • Sperm stored in spermatheca (up to 20 yrs) • Copulation in genital chamber • Accessory glands secrete compounds for eggs Aquatic Insects • Repeated colonizations of freshwater by terrestrial insects • Hemimetabolous: – Mostly aquatic • Ephemeroptera- Mayflies • Odonata- Anisoptera, Zygoptera • Plecoptera- Stoneflies – Mostly terrestrial • Hemiptera or True Bugs • Holometabolous, colonized water more recently – Neuroptera and Megaloptera- Alderflies, Dobsonflies – Trichoptera- Caddisflies (mostly aquatic) – Lepidoptera- Butterflies & Moths – Coleoptera- beetles – Diptera- Flies Male reproductive system • Spermatozoa produced in testes • Sperm stored in vas deferens • Semen or spermatophore transmitted during mating through ejaculatory duct Habitats for aquatic insects • Lotic- flowing water – influenced strongly by velocity of flow • Particle size • Substrate type – Inputs from outside and local nutrient supplies •Lentic- standing water –Often strong zonation •Limnetic zone- penetrated by light •Profundal zone- deeper zone w/o much light 1 River Continuum • Energy inputs • Morphology Unusual habitats • Temporary water bodies (e.g. vernal pools) • Marine environments – Intertidal habitats • Between high and low tide • biting flies, plant feeding insects, detritovores – Littoral habitats • Coastal regions with shallow water • Some midges and beetles – Open ocean- water striders feeding on food of terrestrial origin Ephemeral Water • Seasonal rainfall • Adaptations Marine, Intertidal, Littoral Water • Few truly marine insects How do aquatics obtain oxygen? Oxygen supplies • Air- 200,000 ppm (20%) • Lotic environments (15 ppm) – Depends on O2 production/consumption by plants – Affected by turbulence and water quality • Lentic environments – oxygen levels vary with temperature and salinity – turbulence affects nutrient and oxygen distribution • Anoxic – no oxygen present • Atmospheric oxygen – Keep part of body out of water – Carry oxygen into water • Aqueous oxygen – Use of open tracheal system • Adult insects • Immature forms – Use of closed tracheal system • Specialized structures for gas exchange in water • Often adults have open tracheal system 2 Closed Tracheal System Tracheal system Mosquito larva Dragonfly larva • Gills- lamellar extensions of tracheal system • Found in many insect orders • Gills may be in many places – Base of legs – Abdomen – End of abdomen Mayfly larva Mosquito larva Open Tracheal System in flies • Respiratory siphons near abdomen or thorax • Different location in mosquito pupa than larva Other air bubble gills • Water kept away from body through ‘hairs’ or ‘mesh’ • Oxygen diffuses from water to air against body • Usually slow moving insects with low oxygen demand Open tracheal system in diving beetles • Bubble stored beneath elytra • Gas exchange can occur in water Lotic Adaptations • Flattened bodies • Attachment through suckers 3 Lentic Adaptations More Lotic Adaptations • Taking advantage of surface tension of still water • Nets • Cases Water strider Whirlgig beetle Zonation in lentic habitats Using insects to monitor aquatic environments • Usefulness – Diverse taxa to choose from, many common – Functionally important to ecological community – Ease of sampling many individuals without major ethical constraints – Ability to identify species • Responses – Increases of certain taxa in waters with sediment, low oxygen, increases in temperature – Loss of diversity with pollution and or eutrophication Ephemeroptera mayflies • Wings held above body at rest • Antennae inconspicuous • Often have ‘tails’ • Found near streams • Preserve adults and nymphs in alcohol Odonata dragonflies and damselflies • • • • Immature stages aquatic, adults often near water 4 elongate, many-veined membranous wings Antennae small, bristle-like Pin adults, preserve nymphs in alcohol 4 Hemiptera true bugs Plecoptera stoneflies • Somewhat flat, drabcolored • Wings at rest flat over abdomen • Long antennae • Near streams and rocky shores • Adults, nymphs in alcohol Hemiptera water boatman • Diving or at surface • Adults and immatures both aquatic backswimmer creeping water bug Coleoptera beetles • Live at surface or at bottom • Generally pupate on land • Often predatory Left: Nepidae tails are breathing tubes Right: Belostomatidae egg tending by males Trichoptera caddisflies Diptera flies • Adults resemble moths, but have long slender antennae • Larvae case-building • Wings held roof-like • Adults and larvae in alcohol • 1 pair of wings • Hind wings are ‘knobs’ • Pin or point adults • Larvae in alcohol 5 Neuroptera & Megaloptera 6