ENT101 Fall 2024 Final Study Guide PDF

Prepping for the Final: Below you will find some practice questions for the Ent 101 final exam. You can expect to see questions similar to this on the final. The Coursera and eClass quiz questions also function as excellent practice material, since the exam questions will be quite similar in terms o...

Prepping for the Final: Below you will find some practice questions for the Ent 101 final exam. You can expect to see questions similar to this on the final. The Coursera and eClass quiz questions also function as excellent practice material, since the exam questions will be quite similar in terms of format and the type of knowledge tested. I have included a list of major topics discussed in the course before the midterm, with which you should be familiar. In addition, answers to commonly asked questions about the midterm are included below. PRE-MIDTERM TOPICS: Module 01: Introduction to Insects and their Terrestrial Relatives Arthropods ○ Taxonomy Arthropoda: Jointed appendages Bilateral symmetry Segmented bodies Ventral nerve cord Dorsal blood vessel Exoskeleton Hexapoda: includes all insects and some non-insect groups ○ Characteristics # of tagmata → 3 → Head (sensory organs), thorax (leg + wing attachments), abdomen (organ systems) # of legs → 3 pairs as adults = total of 6 # of antennae → 1 pair Presence of wings as adults (of the arthropods, only insects have wings) Mouthparts → ectognathous (external) mouthparts ○ Evolution and classification First arthropods appeared >520 million years ago (Cambrian period) Early arthropods → spiders, scorpions, millipedes, very similar to what they are today, just bigger First insects appeared ~400 mya Earliest (Carboniferous): dragonflies (Odonata), grasshoppers (orthoptera), true bugs (Hemiptera) Latest (Paleogene): bees (Hymenoptera) 1  ○ Body regions Head (sensory organs), thorax (leg + wing attachments), abdomen (organ systems) Moulting ○ Structure of the cuticle “Top” layer: epicuticle → thin, layers of wax + cement Exocuticle → hardened, pigmented Endocuticle → softer, more flexible Epidermis “Bottom” layer: basement membrane ○ How moulting works Step 1: apolysis → ecdysteroid moulting hormone causes epidermal cells to replicate, separating the old cuticle EMH is released by the prothoracic glands Step 2: digestive fluid is secreted; it breaks down the endocuticle for resorption by epidermal cells It’s used to form new cuticle New cuticle secreted Step 3: Ecdysis: the arthropod increases body volume to push out of old cuticle by contracting muscles The new cuticle must “tan” or harden Arthropod keys to success ○ Small body size Absorbs heat quicker Passive dispersal is easier Muscular efficiency → more efficient ○ Metamorphosis Allows for specialization at different life stages Ametabolous: no metamorphosis Hemimetabolous: egg → nymph → adult ○ Exopterygote (external wings) ○ Odonata (Eg. dragonfly) Direct flight muscles 4 large wings that do not fold ○ Blattodea (Eg. cockroach) Eusocial Leathery tegmina Dorsoventrally flattened Wings fold over body 2  Gut microbes ○ Orthoptera (Eg. grasshopper) Mostly leaf eaters Leathery tegmina Hind legs for jumping ○ Hemiptera (Eg. bedbug) Liquid feeders Piercing sucking mouthparts Hemielytra Holometabolous: egg → larva → pupa → adult ○ Endopterygote (internal wings) ○ Larval state is very different from adult state and occupies a different niche ○ Coleoptera (Eg. ladybug) Very diverse Forewings modified into hardened shells called elytra ○ Hymenoptera (Eg. bee) Hapolodiploid sex determination → eusocial Some have stingers (modified ovvipositor) Chewing lapping mouthparts (for bees) ○ Lepidoptera (Eg. butterfly) Wing hairs modified into scales Many larvae are pests Siphoning mouthparts ○ Diptera (Eg. house fly) Hindwings modified into halteres Some have sponging or piercing suck mouthparts Important disease vectors ○ Diapause Developmental arrest to help survive unfavourable conditions ○ Dispersal capacity Wings, jumping, passive dispersal ○ Reproductive capacity Large number of eggs Short generation time Major insect orders (Complete vs incomplete metamorphosis, Types of development, Characteristics of major orders) 3  ○ Odonata Dragonflies and damselflies Incomplete metamorphosis Aquatic/semiaquatic juveniles Fore and hindwings for flight ○ Blattodea Cockroaches and termites Eusocial Incomplete metamorphosis Hindwings for flight (forewings are tegmina) ○ Orthoptera Grasshoppers, crickets, katydids Incomplete metamorphosis Herbivorous Leathery forewings Hindwings (forewings are tegmina) ○ Hemiptera Half-hardened forewings ‘True bugs” Piercing-sucking mouthparts Incomplete metamorphosis Fore and hindwings ○ Coleoptera Beetles Sclerotized forewings Complete metamorphosis Hindwings (forewings are elytra) ○ Hymenoptera Ants, bees, sawflies Complete metamorphosis Fore and hindwings ○ Lepidoptera Fore and hindwings ○ Diptera “True flies” Complete metamorphosis Halteres → modified hindwings Forewings for flight Insect Collections 4  ○ Their value and purpose Shows how species and/or populations have changed over time Creates the basis for comparison studies ○ Methods of collection Chasing Traps Malaise trap Pitfall trap Lures and baits (pheromones, plant volatiles) Sweep net ○ Preservation Pinning Vials of ethanol Pointing ○ Proper labelling Location Date Collector Taxonomic info Module 02: The Business of Being an Insect I Insect body regions ○ Features of the head Sensory structures Antennae ○ Peripheral nervous system ○ Have sensilla Compound eyes ○ Made of ommatidia Ocelli (single eyes) Mouthparts and mouthpart modifications Labrum Mandibles Maxillae Labium ○ Features of the thorax ○ Features of the abdomen Digestive and excretory system 5  ○ Regions and parts of the alimentary canal Foregut → food is digested and broken down Proventriculus: between fore- and midgut, mechanically breaks down food Midgut → digestion and absorption of nutrients No cuticular lining; lined by peritrophic membrane which encapsulates the bolus ○ Protects midgut epithelium and compartmentalizes digestion Gastric cecae → hold symbionts that help break down things like wood ○ Provides increase surface area Malpighian tubules: removes nitrogenous waste and maintains osmoregulatory balance Hindgut → resorption of water, salts, remaining nutrients ○ Fat body Metabolism of macronutrients Storage organ for nutrients ○ Gut modifications ○ Microbiome Circulatory system ○ Hemolymph doesn’t carry oxygen – gas exchange is a separate system ○ Structure ○ Constituents Dorsal blood vessel Covered in Ostia → one-way valves to the dorsal vessel ○ Blood moves into the ostia and toward the head, then flows to the back of the body Ventral and dorsal diaphragms: guide flow of hemolymph Respiratory system ○ Air flow based on diffusion High to low concentration Tissues us O2 so they have lower O2 concentration than air in tracheoles CO2 is higher in tissues, so is released into tracheoles and hemolymph ○ Structure Tracheae: allow gas exchange Tracheoles: smaller tubes, around tissues with high oxygen 6  demands Spiracles: connect tracheae to outside Air sacs: reservoir to increase ventilation, aid in sound production, and provide room for growth when necessary Expansion/contraction aid air flow in trachea ○ Modifications Module 03: The Business of Being an Insect II Nervous system ○ Structures and mechanisms Neuron: made of dendrites, cell body, and axon Signal received at dendrite and pushed through the axon Sensory neurons, motor neurons, and interneurons Communication at nerve synapse uses neurotransmitters ○ Peripheral nervous system Structures Trichoid sensilla (little hairs) ○ Passes environmental signals through cuticle to neuron ○ Mechanoreception ○ Chemoreception → pores for liquid and gas Olfactory (through air) Contact (through fluid) Types of sensory receptors ○ Central nervous system Structures Brain, ventral nerve cord ○ Brain → 3 pairs of ganglia 1. Associated with optic lobes and mushroom bodies Recieves information from Compound eyes + ocelli Performs central processing/learning (mushroom bodies) 2. Receives and transmits signals from Antennae Olfactory information 3. Receives information from the rest of the body and controls mouth muscles 7  Labrum + foregut, rest of the body (4. Subesophageal ganglion: connect the brain and rest of the central nervous system) Ganglia: bundles of nerve cells ○ Joined by connectives ○ In derived insects, groups in body regions Hormonal regulation Corpora Cardiaca: produces neurohormones that stimulate production of edysteroids by the prothoracic gland ○ Edysteroids: moulting, growth, and development ○ Corpora allata: produces juvenile hormone Juvenile hormone: metamorphosis and reproduction ○ Axonic poisons ○ Synaptic poisons Reproduction ○ Mate finding Chemical cues Pheromones → alter behaviour and/or physiology of conspecifics Auditory cues May accidentally attract predators → risky Visual cues Followed by courtship ○ Courtship Courtship behaviors Dances Appearance Aphrodisiacs Nuptial gifts Food item Spermatophylax: includes nutrients and spermatophore Reproductive system ○ Female organs Ovaries: hold developing eggs Ovarioles: produce eggs Yolk + nutrients Chorion: shell Spermatheca: stores sperm 8  Only non-paired element Accessory glands: produce lubricants + glues ○ Male organs Testes: make sperm Vas deferens: connects testes to seminal vesicles Seminal vesicles: sperm storage Accessory glands: lubrication Aedeagus: external organ ○ Sperm transfer Internal fertilization: Protects gametes, but requires sexual interaction which can be very complex Females make the largest investment, so the male need sto prove they are worth it Courtship behaviours proves the fitness of the mate which can be difficult and dangerous ○ Gifts, displays, exaggerated morphology ○ Sexual conflict ○ ○ Types of sexual reproduction Oviparity Females lay eggs on external surface May be cared for (expensive) or be given defences and left (less expensive) Ovoviviparity Offspring are released from female when they are ready to hatch More investment in eggs but reduces the time that eggs are exposed and vulnerable Viviparity Embryos develop within female after hatching Nourishment is provided from other tissues than the yolk ○ This is the big difference between ovoviviparity and viviparity Costly but best chance of offspring survival Limited number of offspring ○ ○ Types of asexual reproduction Parthenogenesis Unfertilized eggs develop into embryos Polyembryony 9  Single egg splits into many embryos Paedogenesis Bypass pupal and larval form and reproduce as larvae Hermaphroditism Single insect contains both male and female reproductive organs Sexually produce or fertilize self ○ Targeting reproduction in pest management Mating disruption Apply mass pheromones to interfere with mate-finding Sterile insect technique Dilute population with sterile individuals Module 04: Insect Locomotion Dispersal ○ Passive dispersal When an insect’s movement is aided by external sources Advantageous due to lack of energy required to move long distances Wind dispersal Phoresy: transportation of an organism by a larger organism of a different species ○ Active dispersal When an insect expends energy to move itself Increases the chances that an insect will find a suitable habitat compared to passive dispersal Unusual locomotion ○ Water striders Two long rear legs splayed out and two short first legs held in front of the body Mesothoracic legs row the insect along by forming vortices in the water The metathoracic legs steer (like a rudder) Tarsi are covered with densely packed hydrophobic hairs which trap air, increasing buoyancy and allowing the water strider to float without breaking surface tension ○ Marangoni propulsion Stenus beetles excrete a mixture of hydrophobic chemicals when they accidentally drop into water; the chemicals reduce surface 10  tension and propels them forward faster than they are capable of swimming Insect musculature ○ Structures Apodemes: structures on the exoskeleton to which muscles are attached → ridges of thickened cuticle on the inner surface of the exoskeleton Resilin: an elastic protein that allows flexibility in the muscle attachment sites → common at joints such as wings and legs ○ Efficiency Due to the relationship between power and mass, insects’ small size makes their muscles more efficient Insect legs ○ Leg segments (Proximal-most) Coxa Trochanter Femur Tibia Tarsus (Distal-most) Pretarsus ○ Tripod gait 3/6 legs at a time remain in contact with the ground while walking Very stable, centre of gravity remains balanced while walking ○ Leg modifications Cursorial legs: for running Cockroaches Raptorial legs: for grasping and holding Praying mantis Diving beetles Giant water bugs Some assassin bugs Fossorial legs: for digging Mole crickets Saltatorial legs: for jumping Grasshoppers, crickets, katydids (orthopterans) Fleas Some hemipterans Natatorial legs: for swimming Backswimmers (hemipterans) 11  Water beetles (coleopterans) Insect wings ○ Evolution Evolved once Two major groups: Paleoptera (old wing) → hold their wings out to the side or vertically over their bodies Neoptera → can be folded back over the abdomen ○ Wings are protected from physical damage when folded ○ Makes the insect more compact ○ Structure Wing membrane: two thin layers of tightly appressed cuticle Supported by a system of veins → hollow tubules of cuticle ○ Contain tracheae, nerves, and hemolymph ○ Allow nutrient transportation and gas exchange within the wing ○ Wing modifications Tegmina: thick, leathery forewings Used for protection and steering Can be used for sound production Can be used for camouflage Grasshoppers, mantises, and cockroaches Hemelytra: proximal portion of the forewing is leathery Some hemipterans Aphids, cicada Provides some additional protection Elytra: completely sclerotized forewings Protective Unique to coleopterans Makes these insects weak flyers, but they provide some stability and lift in flight Scales: highly modified setae (hairs) covering the upper and lower surfaces of the wings Set in sockets at an angle to the wing surface Colourful (structural or pigment) Camouflage, mimicry, mate attraction, thermoregulation, protection ○ Easily dislodged = quick escape 12  ○ Absorbs radiant energy from the sun (if darkly coloured) Some have androconia → specialized wing scale containing aphrodisiac-producing glands Halteres: knob-like hindwings used like gyroscopes to improve stability in flight True flies = Diptera Makes flies extremely agile Contains many campaniform sensilla Flight musculature ○ Direct vs indirect Direct: flight muscles attach directly to sclerites to power wing movement Upstroke → muscle attached proximally to the pivot point contracts Downstroke → muscle attached distally to the pivot point contracts Highly agile flight Indirect: distorts the thorax to initiate wing movement Upstroke → dorsoventral (up and down) muscles contract Downstroke → dorsal longitudinal (front to back) muscles contract ○ Synchronous vs asynchronous Synchronous: each contraction cycle is directly stimulated by a neural impulse Asynchronous: do not need direct nervous stimulation for each contraction cycle → stimulation of muscles releases tension in one muscle, which stimulates the contraction of the other Tools for studying insect flight ○ Digital particle velocimetry Precisely analyze the flow field around an insect wing and the forces produced ○ Flight mills Central post with a sensor, an insect is tethered to a lightweight arm that spins as the insect flies. Can be used to determine relationship between flight propensity/distance and semiochemical exposure, mating status, body weight, wing size, or fat content ○ Wind tunnels 13  Can study the response of insects to olfactory and visual cues in flight Large, mostly empty fume hood/box Lights and fans for wind Flight pattern is recorded Insect migration ○ Persistent movement ○ Relatively straight direction ○ No stopping regardless of stimuli ○ Pre and post migratory behaviours ○ Involves physiological changes ○ Not considered dispersal → movement of entire populations ○ Biological and physiological adaptations Migratory syndrome → environmental cues alter the insect’s energy allocation and locomotory ability Presence of wings, larger wings Reproductive diapause → oogenesis-flight syndrome ○ Phases of migration 1. Initiation 2. Transmigration → sustained flight phase 3. Termination ○ Locust migration Population densities are high = gregarious and migratory form of grasshoppers called locusts Polyphenism Aggregation, daytime flights, long-distance migrations Higher metabolic requirements, shorter lifespans, fewer eggs per egg pod ○ Monarch migration Oogenesis flight syndrome triggered by suppression of JH Southward part → single generation followed by overwintering Return northward → multiple subsequent generations Relies on circadian rhythm Internal compass based on solar cues Module 05: Insects as Decomposers Nutrient cycling Detritivore feeding guilds + Adaptations for these lifestyles ○ Mainly cycle carbon, nitrogen, and phosphorous 14  ○ Xylophagy = wood Digest cellulose with aid of symbiotic gut microbes Microbes passed on through trophallaxis (mouth to mouth or hindgut secretions) ○ Coprophagy = dung Rich source of nutrients but short lived Adults: powerful senses and can have biparental care For detection and protection of rare resources Larvae: often live-born or hatch quickly Dung beetles are important in the breakdown of dung ○ Necrophagy = carrion Similar to corpophages, but must deal with vast competition and bacteria Insect development ○ Moulting ○ Metamorphosis ○ Voltinism ○ Degree-day models Forensic Entomology ○ Stages of decomposition Fresh – blow flies, flesh flies, house flies, some carabid beetles Putrefaction – cheese flies, faniid flies, rove beetles, carrion beetles, hister beetles, checkered beetles Black putrefaction – maggots exit to pupate; adult flies leave; beetles dominate Butyric fermentation – flies have pupated; replaced by beetles and predatory mites Dry decay – dermestid beetles and incidental species ○ Estimating post-mortem index Using degree-day models 1. Collect arthropod colonizers from the corpse ○ First wave: all life stages can provide info 2. Species identification of the initial colonizers ○ Often identification is done genetically – some are reared to adulthood for easier identification ○ Can then use the correct degree day model 3. Estimate the developmental stage at which the insects were collected ○ Use morpholou (dry weight, ehad capsule, etc) 15  4. Collect short-term climatic data ○ And other potentially important conditions 5. Calculate degree days ○ Use developmental threshold and climate data 6. Estimate PMI ○ Use degree days and any other info collected Using insect succession ○ Other information provided ○ Challenges Module 06: Plant Feeding and Impacts of Herbivory Coevolution ○ Evolution influenced by 2 or more species ○ Specific vs diffuse Specific: relationship between just two species (one plant and one herbivore, for example) Diffuse: multiple species influenced by one or more other species ○ Ecological fitting Pre-existing traits “fit” newly encountered ecology Can lead to host race formation New adaptations arise in response to a new host May lead to speciation ○ Host race formation As a population begins to specialize on new organisms, it becomes separated from the original population Diet specialisation ○ Monophagy = one food source May be difficult to locate food source Less resource competition Requires physiological specialization Can provide defensive benefits ○ Oligophagy = limited plant food sources Still relies on the presence of resources Also are able to overcome a degree of defences and use plant chemicals ○ polyphagy = many food sources Generally less limited by resources More susceptible to some plant defences 16  Plant defences ○ Constitutive vs induced ○ Physical defences Trichomes Specialized hairs on the plant Non-preference defence Leaf toughness Silica Resins ○ Chemical defences Secondary plant metabolites Metabolites not used in growth and development Many different purposes Toxins for antibiosis Attraction of predators/parasitoids to prey on herbivores Resins Antibiosis Interrupts metabolism ○ Mutualistic relationships Myrmecophytes Ants as defense → ants live inside the plant and defend it against attackers ○ Behavioral defences Herbivore feeding guilds + Adaptations for these lifestyles ○ Defoliators Eat leaves → biting and chewing mouthparts ○ Leafminers Feed and live between layers in a leaf Dorsoventrally flattened with forward-facing mouthparts ○ Seed/fruit feeders Various feeding styles (chew, suck, bore) Considered predators since they are killing the organism ○ Sap feeders Feed on various sap fluids Piercing-sucking mouthparts ○ Root feeders Larvae eat externally or burrow into roots ○ Stem feeders Powerful biting and chewing mouthparts 17  ○ Gall formers Induce galls on plants by physically altering the growth of the plant through feeding/injection → increases cell size and/or numbers Impacts of herbivores ○ As pests Invasive species ○ As weed control POST-MIDTERM TOPICS: Module 07: Pollination and Beekeeping Pollination ○ Entomophily: insect pollination ○ Gymnosperms: non-flowering plants; pollinated by wind and water (some insect pollination) ○ Angiosperms: flowering plants, also pollinated by insects ○ Evolutionary history Before flowers, wind and water carried pollen to fertilize plants Angiosperms evolved with complex reproductive organs Insects and plants coevolved Beetles were the first pollinators Early flowers were bowl-shaped to facilitate landing Generalists vs specialists Generalists: more resilient system but less efficient pollination Specialists: more reliance, but insect gets exclusive access and plant is more likely to be fertilized ○ Animal pollination More targeted and efficient than wind pollination Pollinators travel toward flowers Plants that use animal pollinators don’t need to produce as much pollen as wind-pollinated plants (saves energy) Drives the evolution of specialized reproductive structures ○ Pollinator cues Flowers are brightly coloured, which makes them easy to locate Nectar guides → markings that direct pollinators to nectaries at the bases of flowers ○ Often reflect UV light 18  Scent → helps for low light conditions or in environments with low visibility ○ Necrophagous insects can be tricked into pollinating flowers that give off corpse smells Can also be red and warm like a carcass Insect mimics → mimic potential mate Challenges Faced by Pollinators ○ Habitat loss Driven by growth and spread of agriculture and industrial development Reduce floral diversity and abundance → less food ○ Insecticide use Non-target impacts Neonicotinoids Safe for vertebrates Can be applied to coat the seeds of the crop plant so that they are taken up by the roots once growth begins ○ Systemic insecticides ○ Poisons herbivorous insects when they eat the plant ○ Also exist in the nectar and pollen May not kill bees, but can impact the bee’s ability to learn ○ Ability to return to nest ○ Ability to find mates Heavily applied to ornamental plants Managed Pollinators ○ 4 types of managed pollinators European Honey bees → honey production and wax Bumble bees → buzz pollination for greenhouses Leafcutter bees → solitary Megachile rotundata → used as pollinators because they’re a bit more robust than honey bees, which is important for alfalfa ○ Alfalfa has defense mechanisms that hits bees in the face and cover them with pollen Osmia lignaria → mason bees, pollinators of fruit trees, only visit flowers a short distance from the nestin site ○ Easy to direct bees to the target crop Apiculture ○ History 19  Honey bees are the first domesticated bees Earliest documentation is a painting in Spain from 9kya ○ Purpose Honey Bee pollen Nutritional supplement Royal jelly Supplement + cosmetic product Beeswax Cosmetic product Pollination services ○ Types of honey bees European honey bee Nest in natural cavities = easy transition to human-made hives Generalist pollinators Produce large quantities of honey Can regulate colony temperature, allowing for overwintering African honey bee Aggressive defenders Great honey production Does well in tropical climates Africanised honey bee Intentional cross of African and European honeybees (with unintentional consequences) Can take over other honeybee hives Same sting but aggressive behaviour More guards Asiatic honey bee Can deal with giant northern hornets (buzz and smother) ○ Bees can decouple their flight muscles from their wings and vibrate, raising their body temperatures by as much as 10 degrees. They can swarm intruders to the hive and raise temps and CO2 levels to cook and suffocate them Smaller than European honey bee Can tolerate lower temperatures More resistant to parasitic mite infestations 20  Giant honey bee Nests in the open under rock faces or tree branches ○ Hard to domesticate since they nest in the open More aggressive than European honey bees Produce a lot of honey Dwarf honey bee Nests in the open Do not produce much honey Coat tree branches with propolis (beeswax and saliva) which traps any foraging ants The Eusocial Societies of the Honey Bee ○ Eusociality: 1. Cooperative brood care whereby individuals care for offspring that are not their own 2. Overlapping generations in which offspring assist the reproductive(s) with colony tasks 3. A caste system whereby the colony is primarily composed of individuals that do not reproduce and only one or a few reproductive individuals ○ Haplodiploidy Males develop from unfertilized eggs (haploid – one set of chromosomes) Females develop from fertilized eggs (diploid – two sets of chromosomes) ○ Honey bee castes Workers All female Most populous group Do all the labour tasks ○ Foraging, brood care, hive defence ○ Start as nurses → become guards → as they’re older they become foragers Can ley eggs but can’t mate – all their babies will be male (doesn’t occur unless the queen is removed) Stinger = ovipositor Queen Only one who reproduces Reared in special queen cells and fed royal jelly Once she emerges from her cell, feeds and searches for 21  mates Takes up to 15 nuptial flights ○ Mate in midair with multiple males ○ Gives her enough sperm to fertilize up to ~1500 eggs a day for 3-4 years Drones Male honey bees Only purpose is to mate Super large eyes to spot queens Highly sensitive antennae to detect queen’s sex pheromone No stinger No pollen basket Short proboscis Caste determination Sex is determined by the number of sets of chromosomes Caste is determined by nutritional components in the food provided to developing larvae ○ No difference between eggs ○ Cell shape determines: Fed worker jelly vs royal jelly amount of food ○ These two factors alter JH levels and causes them to grow differently Cell shape is determined by queen’s activity Honey Bee Biology ○ Adaptations for foraging Chewing lapping mouthparts Mandibles used to build, maintain, and defend hives, manipulate food and wax Pollen collecting structuring on their hind tibiae called pollen baskets Excellent vision with ultraviolet range Can also detect polarized light ○ Honey How it’s made Bees regurgitate nectar to each other so that each bee can add more digestive enzymes to help break down the nectar It is deposited into a cell Workers fan the nectar with wings to evaporate extra 22  moisture Workers then cap and seal the cell with wax Other attributes Low water content + acidic nature = inhospitable to fungi and bacteria ○ Can remain edible for centuries to millennia ○ Swarming A new colony is formed by an abundance of individuals The swarm contains a queen and searches for a new nest site Before a swarm forms, there must be more than 1 queen An egg is put into a queen cell so that a queen rears at the same time as the swarm forms Workers feed the existing queen less and push her around, forcing her to lose weight so that she can fly Workers eat more to survive the flight Once the swarm cluster forms, scouts with search for new potential build sites Honey Bee Communication ○ Dance Round dance: simplest dance Advertises food close to the nest, usually within 15m Dancer moves in a circular pattern and offers pollen and nectar, giving observers the scent Alerts observers to food in the area, but not where Waggle dance: communicates precise information to other bees Direction and distance of far away food Figure eight pattern during which the bee waggles her abdomen The waggle phase corresponds to the direction of food at an angle relative to the sun Length of the waggle phase tells observers about the relative distance ○ Communicated in terms of the amount of effort required More pollen and nectar = more waggles in the dance Dorsoventral abdominal vibration dance (DVAV) Thought that the dance is used to regulate foraging activities in response to seasonal food availability 23  May also influence emergence of new queens or initiate swarming behaviour ○ We don’t really know ○ Pheromones Nasanov’s gland in abdomen or Tarsal glands in the tarsi produce footprint pheromones Attract bees to places Mandibular and abdominal glands produce alarm pheromones Released when worker bees defend the hive against raiding bees or other animals Queens produce the queen mandibular pheromone constantly Informs the colony of a healthy queen and inhibits egg production in workers She also has chemicals that inhibit queen cell construction, allow workers to recognize her, and that influence swarm behaviour Also produces sex pheromones Larvae also produce pheromones that indicate their presence to nurses Threats to European Honey Bees ○ Biological threats Colony Collapse Disorder Occurs if the majority of workers abandon a hive, leaving behind the queen, brood, a few nurse bees, and the food Cause and validity is debated ○ Poor quality management? Varroa mites External parasites that feed on the fat body of adult and larval honey bees Only mature females are seen by beekeepers (haplodiploidy) Carry many diseases, including wing virus Tracheal mites Very small → live inside the tracheae of honey bees ○ Pierce the tracheal wall and feed on the bee’s hemolymph Mate inside the tracheae Disperse through contact between bees Create wounds as they feed, which can become infected 24  Presence of mites impact gas exchange in the bee Treatment against Varroa mites also treats tracheal mites Fungi Chalkbrood disease, caused by the fungus Ascosphaera apis Only affects larvae but can be transmitted between other bees If the gut flora in the larva isn’t enough to compete with the fungal spores ingested, the fungal spores germinate and kill the larva. Viruses Deformed wing virus is vectored by Varroa mites Cause bees to die as pupae or soon after eclosing Bees that survive to adulthood are unable to fly Bacteria American foulbrood affects larval bees ○ Caused by bacteria Paenibacillus larvae ○ Highly contagious and very destructive ○ Spores are ingested, then germinate in the midgut and absorb nutrients from the host ○ No cure ○ Other Issues Agriculture Reduces flower diversity ○ Doesn’t provide the diversity of pollen and nectar for a healthy bee colony Insecticide use Can contaminate nectar and pollen Neonicotinoids are banned in many countries for weakening and killing bees ○ Helping Honey Bees Beekeepers must provide timely and sufficient carb sources after harvesting honey to prevent starvation Place hives near a diversity of flowers Limit exposure to insecticides Apply at non-active intervals of the day to minimize exposure Leave untilled ground, unmowed fencelines, and hedgerows around farm fields to provide habitats for pollinators 25 Module 08: Insects and Disease Insects as Etiological Agents ○ Etiological agent: organisms that directly cause disease in another organism Flies and other irritants cause stress Bites and stings Bedbugs, parasitic flies (botflies), scabies mites and lice Act like a disease but don’t transmit diseases May also cause exsanguination in large numbers Secondary infection is always a risk ○ Disease: a disorder of structure/function not just caused by physical injury; usually affects a specific location ○ Disease vector: carries and transmits disease-causing organisms ○ Pathology: involves the development, cause and effect of diseases ○ Arthropod examples Bedbugs Bed bugs do not transmit pathogens but bite and cause stress Lice Blood feeders – can cause severe itchiness Historically were vectors of epidemic typhus Ticks Lyme disease ○ Ways in which insects can act as etiological agents Anxiety and stress from insects around the eyes, nose, and mouth can cause a loss of appetite and self-injury (livestock) Phobias Entomophobia Delusional parasitosis – the individual is convinced that they are being attacked by insects or other parasites Bites and stings can range from annoying to causing mild to severe injury Exsanguination – severe blood loss from biting insects Invade host tissues – subcutaneous tissues or internal organs Can be ingested or inhaled Insects as Disease Vectors ○ Types of hosts Definitive host: the disease-causing organism sexually reproduces 26  within the host Intermediate host: the disease-causing organism does not reproduce sexually within the host Asexual reproduction may occur ○ Routes of disease transmission Mechanical Occurs through direct physical contact between vector and vertebrate host; no biological relationship ○ The disease-causing organism doesn’t undergo any development or reproduction on or within the vector Number of infectious units + probability of disease transmission decreases over time Biological Involves some development or reproduction of the disease-causing organism within the arthropod vector Number of infectious units + probability of disease transmission increases over time Horizontal Movement of disease-causing organisms between hosts and vectors/between vectors within the same generation (between individuals) Vertical Movement of disease-causing organisms between generations of either the vector or the host (parent to offspring) ○ Vector competence A vector’s ability to acquire, maintain, and transmit the disease-causing organism ○ Invasive vectors and emerging diseases Invasive arthropods may not have the same level of vector competence in the new range Asian longhorn tick has been found in eastern US → vectors several human and animal diseases Determine potential range expansion and vector competency in new range ○ Look at ecology, habitat, and feeding preferences Trade and travel have impacted the incidence of emerging vector-borne diseases carried by arthropods Deforestation and other human activities can change transmission 27  dynamics Climate change can influence vector-borne outbreaks → temperature + humidity influence development, abundance, spread, and distribution of disease-causing organisms, vectors, and hosts Arthropod-borne Human Diseases ○ Morbidity: being sick ○ Mortality: measure of deaths in a population ○ Medical entomology: studies the impacts of insects and other arthropods on human health Investigates behaviour, ecology, and biology of arthropod disease vectors Also study the epidemiology of arthropod-borne diseases ○ Historical impacts on war More soldiers died from diseases during WW2 than from battlefield injuries (unhygienic conditions of the battlefield) ○ Major epidemics Epidemic typhus Vectored by the human blood louse → disease-causing bacteria is an intracellular parasite that damages cells lining blood vessels ○ Causes fever, rashes, and muscle aches ○ Patient slips into a coma and dies ○ 10-60% mortality rate May have killed up to 50% of Napoleon’s soldiers in 1812 ○ Contributed to the failure of the French invasion of Russia ○ Killed >3 million people in WW1 and Russian Revolution Classified as a bioterrorism agent Plague Vectors: oriental rat flea and the human flea Bacteria invades lymph nodes; they swell and break open, spreading to the bloodstream and lungs Justinian plague, Black Death, current outbreak in China and India ○ Modern human diseases Lymphatic filariasis AKA elephantiasis 28  Disfiguring disease ○ Causes extreme tissue swelling and thickening of skin on limbs, chest, and genitals Caused by filarial nematodes → roundworms ○ Transmitted by female mosquitos Low mortality but high morbidity Preventative chemotherapy and deworming drugs Malaria Caused by protozoan parasites, vectored by female mosquitos High mortality in children, but pregnant people and HIV patients are also at risk Causes anemia and multiple organ failure Malaria transmission cycles are interrupted by mosquito nets and insecticides to target the insect vector ○ Supplemented with antimalarial drugs ○ Emerging human diseases Zika Can cause congenital brain abnormalities and other severe disorders in a developing fetus Mosquito vectors Lyme Caused by bacteria Vectored by ticks Multisystemic disorder → varying symptoms Swift diagnosis and treatment is crucial ○ Can cause severe chronic neurological and heart complications Arthropod-borne Animal Diseases ○ Insects as etiological agents of animals Mange → caused by feeding activity of some mite species on and within the skin causing persistent inflammation Causes itching, lesions, and hairloss from scratching Spread through physical contact Treatment is expensive ○ Insects as vectors of animal diseases Dog heartworm Transmitted by mosquitos to a dog host → caused by filarial nematodes 29  Larvae mature in the canine’s heart, blood vessels, and lungs Cause exhaustion, reduced lung function, and death Treatment can be costly but preventative medications are available Bodies of dead worms after treatment can still cause problems Can infect humans, but they can’t be transmitted from a human Bluetongue Vectored by biting midges Mainly affects sheep but also other ruminants Causes cyanation of the tongue and other significant symptoms Usually leads to death Nagana Caused by trypanosomal parasites; vectored by tsetse flies In cattle, infect the red blood cells and cause fever, weakness, and lethargy Infected animals are useless as working animals High mortality rate Arthropod-borne Plant Diseases ○ Viral Types of viral plant disease transmission Non-persistent → the viral particles are only on the mouthparts of the insect vector ○ From one feeding to next feeding ○ Remain infectious for a short period of time ○ No incubation period required ○ Mostly by aphids Semi-persistent → retained in the insect’s foregut (and mouthparts?) but not tissues ○ Do not circulate or replicate within the vector ○ Don’t usually require a long incubation period Persistent → maintained within a vector for the remainder of its lifespan ○ Virus circulates and replicates within various organs ○ Transmission may require extended feeding to become infectious 30  ○ Virus enters midgut and hemocoel and colonizes other tissues ○ Can be passed from female vectors to offspring if it infects the ovaries ○ Leafhoppers transmit viruses like this Potato leafroll virus ○ Bacterial Fire blight Particularly destructive to apples and pears Caused by bacteria → can colonize any tissues of the plant ○ Causes tissues to wither and darken and look scorched ○ On fruits, produces a bacterial ooze Can disperse by wind or rain to new tissues and plants Insects can pick up the disease through feeding activities ○ Fungal Dutch elm disease Not native to North America; American elm trees have not coevolved and cannot tolerate the infection Vectored through a few species of elm bark beetles Caused by a fungus ○ Grows in vascular tissues of trees, blocking water and nutrients and causing die-off around the infection ○ Can kill weakened trees in months Module 09: Sustainable Human-Insect Interactions: IPM Integrated Pest Management ○ IPM integrates multiple control methods to manage pest populations ○ The Four-Tiered IPM Implementation Approach 1. Economic/action thresholds Level of a pest population that will require managers to implement control measures to prevent losses ○ Can be measured by estimating number of pests ○ Can be measured by other easier to notice factors like damage to the ecosystem ○ Generally, don’t control when populations are below the ET 31  However, start to control before pest densities rise above the economic injury level The economic injury level is slightly higher than the economic threshold 2. Identification and monitoring Monitoring efforts occur before the implementation of control measures, but continue during and after controls have been applied ○ Direct surveillance or monitoring pest activity/damage Correct identification of the pest is necessary for monitoring and control Sampling methods ○ in-situ sampling: on the ground looking at individuals involves manual inspection of the affected resource for the insect or its associated damage Laborious Efficient – needs few samples ○ Sweep netting: general sampling in field ○ Knockdown method: trees in orchards plant is struck and insects fall to a tray or sheet underneath Sometimes gaseous chemical helps dislodge them ○ Passive traps: general monitoring provide a sample of natural insect movement and distribution in the managed area monitoring traps that attract insects can assess population density at low population densities over a large area, and remain effective for a long period of time Trapping insects also allows managers to preserve insects and count them at a later date ○ Pheromone baited traps: for specific pests often baited with attractive visual and chemical cues that lure in the target pest species Tends to be sex-specific 3. Prevention 32  Considered the first line of defence in pest management Regulatory practices, quarantine regulations, and other preventative tactics Limit goods movement ○ Quarantine + inspection ○ Sanitation and removal of infested plants ○ Selection of resistant crops 4. Control Effective IPM programs integrate multiple control methods together Evaluated based on economics, efficiency, effectiveness, human health risks, and environmental risk. Insecticide Usage ○ Pesticides must be evaluated by managers using several criteria: Safety for the user Species specificity Effectiveness/efficiency Persistence of the chemicals in the environment Speed of action Cost of use ○ Modes of insecticide application Stomach poisons must be ingested in order to impact the insect, and so can be applied to the resource that the insect uses as a food source ○ Some stomach poisons are even applied as systemic insecticides so that they are absorbed by the plants and become present in all of its tissues Neonicotinoids (remember the pollination module) Contact poisons penetrate the insect cuticle to enter through the body wall the insect needs only to crawl over a treated surface to absorb the poison through contact. contact poisons tend to be ineffective for insects that feed within a plant Synthetic chemicals, such as the synaptic poison Malathion, can also be contact poisons Fumigants 33  Fumigants are insecticides that are gaseous above 5 degrees celsius, applied as a sort of vapour or smoke to the area The poison enters the body of an insect through the spiracles and invades the tracheal system, from which it can be absorbed into the body tissues Can kill all life stages, including eggs Can reach areas not reached by sprays Primarily applied in enclosed environments ○ Some are toxic to humans and others ○ Types of chemical insecticides Natural insecticides Sulphur is attractive to pest managers due to its low cost, high availability, ability to mix with other pesticides and species specificity. ○ Low effect on bees and humans Most natural insecticides are natural botanicals ○ Toxins against herbivory produced in specific parts of the plant ○ Pyrethrins are broad-spectrum → affect a wide range of insects but low mammalian toxicity (safe for humans) ○ Nicotine → toxic to both insects and mammals ○ Collection can be costly ○ Natural insecticides tend to break down easily in the environment and need to be reapplied often ○ Synthetic insecticides We can manipulate features to make them more useful More effective against pests than other compounds Reduce their impacts on non-target organisms (humans) Selected based on: ○ Modes of action ○ Impact on insect physiology Axonic poisons impact the transmission of action potentials along the axons of nerve cells Disrupts the balance of sodium and potassium influxes along the axon’s membrane DDT → developed in WW2 (chlorinated hydrocarbon) 34  ○ Broad spectrum ○ High chemical stability, fat soluable Accumulates in fatty tissues and not excreted with waste → increases in higher trophic levels (biomagnification) ○ Potentially carcinogenic ○ Lowers reproductive success in humans ○ Eggshell thinning in birds → drops in predatory bird populations Pyrethroids → mimic pyrethrins (oids = synthetic) ○ Toxic to inverts but not vertebrates ○ Fast acting ○ act as axonic poisons by keeping the sodium channels in the axons open, preventing a sodium gradient from being established across the axon membrane. interrupts transmission of nervous impulses, which causes a loss of locomotory function, tremors, and a loss of control over the nervous system ○ Higher stability than natural counterparts but don’t persist in the environment for long Doesn’t accumulate in the environment Synaptic poisons Disrupts nerve impulses at the synapses (junctions between nerve cells) Organophosphates ○ inhibit acetylcholinesterases, which break down the excitatory neurotransmitter, acetylcholine ○ As the neurotransmitters are not broken down by enzymatic activity, they stay in the synapse and cause constant stimulation of acetylcholine receptors in the dendrites of the receiving neuron causes rapid nerve firing, tremors, and death ○ Highly effective ○ Break down in UV → don’t bioaccumulate ○ Can be toxic to vertebrates 35  Used for mosquitos that transmit West Nile Virus but not in home gardens ○ Ex. Malathion Neonicotinoids ○ cannot be broken down and cleared by the enzyme acetylcholinesterase ○ results in the post-synaptic acetylcholine receptors being continuously activated and resulting in similar symptoms as organophosphate poisoning. ○ Low mammal toxicity ○ Linked to the decline of bees and other pollinators ○ Can mitigate the development of resistance to other poisons when alternated Muscle poisons act by depleting calcium stored in muscle cells through activation of the receptors that stimulate calcium release. ○ Leads to paralysis and death Chlorantraniliprole ○ Can impact any life stage in most species ○ Kills after contact or ingestion ○ Minimal impacts on pollinators, detritivores, and natural enemies ○ Safe for user Hormone analog insecticides Disrupts growth and metamorphosis Analog of Juvenile Hormone ○ Interferes with metamorphosis ○ Larva may produce extra, larger instars instead of JH dropping and triggering transition from larva to pupa Unable to moult into reproductively capable adult ○ Especially effective against insects that are pests as adults Ecdysteroids → mimic ecdysone ○ Binds to moulting hormone receptors 36  Cannot be cleared from receptors → process is disrupted Insects cannot finish their moults and die Little effects on vertebrates and non-target organisms ○ Many are specific to certain insect groups ○ Flexible application timing Limitations of Insecticide Use ○ Non-target effects Pollinators can ingest insecticides present on flowers or systemic insecticides Predators can come into contact with these poisons as well Insecticides that leach into water systems can kill aquatic arthropods, and even larger animals like fish and amphibians broad-spectrum insecticides and neurotoxins can be dangerous for larger animals the neurons of vertebrates function in much the same way as they do in insects Disposal: Pesticide-contaminated wastes are dumped into a designated biobed area, which is filled with a mixture of plant material and soil that provides an excellent habitat for microbes which break down pesticide residues. ○ Resurgence 1. Broad-spectrum insecticides are applied to a managed area to kill pests 2. Insecticide kills natural enemies (predators and parasitoids) Natural enemies take a long time to recover (reliant on other species) but herbivore populations can recover quickly 3. The herbivorous population surges due to lack of natural enemies keeping them in check Has occurred with strawberries in the US and Cyclamen mites ○ Replacement 1. Broad-spectrum insecticides are applied to a managed area to kill pests 2. Insecticide kills natural enemies (predators and parasitoids) Natural enemies control both target pest and other herbivorous species 3. Previously non-problematic herbivorous insects surge to populations higher without natural enemies, and thus become a 37  pest Spider mites: pyrethroids used against thrips but also eliminated non-target arthropods, allowing spider mites to move in ○ Resistance a reduction in the sensitivity of a pest population to a particular method of pest control, typically chemical controls such as pesticides occurs through genetic means and arises due to natural selection Happens anytime that offspring aren’t genetic clones Pests that have a limited range of resources and disperse over only short distances can face greater exposure to insecticides, and thus a greater selective pressure to evolve resistance to the poisons If a pest species has short generation time/produces lots of offspring, there is a higher likelihood that individuals resistant to the insecticides will appear in the population Operational factors: Setting low economic thresholds can increase the rate that resistance develops If the chemical is applied before mating, only resistant adults get to produce offspring and pass on their genes Mechanisms of resistance ○ Behavioural resistance When a pest species modifies its behaviour in a way that decreases its exposure to a toxin Location of habitation/oviposition Slowed feeding ○ Metabolic resistance Most common the poison is detoxified or destroyed by enzymes in the insect before it can reach its target site of activity Sometimes excreted/molted Sometimes sequestered ○ Altered target site resistance 2nd most common changes to the receptors to which the insecticides normally bind, making them less receptive to the poison occurs in response to treatment with hormone analog 38  insecticides ○ Penetration resistance adaptations to the exoskeleton that decrease penetration of the cuticle by insecticide can make other forms of resistance, such as metabolic resistance, more effective Thicker exoskeleton, hydrophobic wax layer Often linked to other mechanisms Occurs in some populations of Anopheles mosquitos ○ Cross-resistance an organism develops a resistance to an insecticide, which in turn allows it to tolerate other insecticides as well, even if it hasn't been exposed to them. Has occurred in some house fly populations that were heavily exposed to DDT and became resistant to other types of axonic poisons, such as pyrethroids ○ Slowing resistance The best way to do so is through an Integrated Pest Management system that relies on a concert of techniques to control pests rather than traditional chemical controls alone alternate the application of insecticides with different modes of action a mutation that allows an insect to resist one type of insecticide in one season will be useless during the next season when an insecticide that acts on a different biological system is used Provide a refuge for the pest population that is insecticide-free Immune and susceptible individuals mate to produce some offspring that are still susceptible Resources can be supplemented that support natural enemies → no selective pressure Module 10: Sustainable Human-Insect Interactions: IPM (Biological and Cultural Control) Concepts Underlying Biological Control ○ affects pest populations through naturally occurring trophic interactions refers to an organism’s position within a food web 39  Four basic trophic levels: 1. Autotrophs = producers (plants) 2. First-order consumers = herbivores 3. Second-order consumers = carnivores that eat herbivores 4. Third-order consumers = carnivores that feed on other carnivores ○ In most pest management situations, the herbivore is the management target. These are kept in check by natural enemies in the third trophic level can include predators, parasitoids, parasites, and pathogens such as bacteria, viruses, and fungi achieved by introducing, augmenting, or conserving populations of natural enemies within a managed habitat Biological Control Agents ○ When natural enemies are recruited or managed by humans in order to reduce pests populations ○ Parasitoids insects that are parasitic as larvae, and eventually kill the arthropod host in contrast to parasites, which do not normally kill the host to complete their life cycle Some are generalists and some are specialists Affect fewer ton-target species that insecticides Have specialized host-finding → but dependent on oviposting females Most used as BCA are Hymenoptera and Diptera, some Strepsitera Types of parasitism Endoparasitoids: develop within the host and feed on internal tissues Ectoparasitoids: live on the host and feed from outside Koinobiont: develop while the host continues to feed and grow Idiobiont: inhibit the development of their hosts ○ Most are ectroparasitoids Superparasitism: a host is attacked multiple times by individual parasitoids of a single species ○ Uncommon → introduces intraspecific competition 40  Multiparasitism: Parasitoids of multiple species parasitise a single host simultaneously ○ interspecific competition between larvae of different parasitoid species usually results in only a single species completing development Hyperparasitism: parasitoid larvae or pupae may serve as a host for yet another parasitoid species ○ occurs at the fourth trophic level Dealing with the host’s immune response Encapsulation: hemocytes form a cover over the foreign body (the parasitoid) → kills egg or larva by cutting off nutrients and oxygen ○ Some dipterans hijack it and use it for protection Evasion: Endoparasitoids can evade a host’s immune system is by carefully placing offspring in regions within the host’s body that have a weak immune response ○ eggs oviposited within the ganglia of the host’s central nervous system are shielded from host immune responses Immunosuppression ○ parasitoid wasps harbour symbiotic viruses that are injected into the host with their eggs Polydnaviruses infect the host and suppress its immune responses, allowing the parasitoid larvae to successfully complete development within the host Behaviour manipulation ○ Bodyguard manipulation: The host is not killed, even after the wasps emerge to pupate, but instead its behaviour is modified to protect the pupae Guards pupae Defends pupae Seek shelter before pupation or use silk to spin a protective cocoon ○ Predators free-living organisms that feed on other animals, killing their prey more rapidly than parasitoids require multiple prey items to survive, and therefore attack and kill several animals in their lifespan 41  most predators feed on multiple prey species Ladybird beetles, predatory mites, and lacewings added benefit of being predators in both larval and adult stages, unlike parasitoids, which only feed on hosts during their larval stages Generalist predators are typically most effective when pest populations are low. At high pest densities, generalist predators can not keep up with prey populations. ○ Pathogens Bacteria The bacteria enter the pest species and may release toxins that kill the insects ○ Bacillus thuringiensis or Bt is widely used naturally occurs as a soil-borne bacterium Applied to the surface of plants, must be ingested by the insect produces crystals that contain endotoxins which damage and paralyze the midgut Causes starvation and infection → guts leak into hemocoel Fungi Once the spores land on and attach to the insect’s exoskeleton, they germinate and penetrate the cuticle, gradually infecting the hemocoel, and typically killing the insect in the process. Beauveria bassiana is a species of fungus commonly used as a biological control agent Viruses Infect and replicate within the cells of a living organism, and can kill them in the process ○ Many only attack insects and break down quickly in the environment Used to control gypsy moths and codling moths ○ Other biological control agents Manipulating endosymbionts We can inlict various kinds of effects on insect pests by disturbing or manipulating the microbiome of endosymbionts ○ effects may include decreased growth rates, 42  diminished reproductive success, or even a reduction in the ability of insect vectors to transmit diseases Three techniques: ○ introduction of novel microorganisms into an insect’s microbiome has been done in Aedes aegypti mosquitoes → negatively affect the mosquito’s reproductive success, and ability to transmit dengue fever ○ Genetic modification of microorganisms already present in the pest species genetically modified E. coli have been introduced into the kissing bugs that vector of Chagas disease After ingestion and establishment in the microbiome, the modified bacteria make molecules that interfere with natural gene expression in the insects ○ disrupt protein synthesis that causes a reduction in oviposition success ○ increase in juvenile mortality. ○ Elimination of microorganisms If we can remove symbionts on which a pest relies for growth, reproduction, or survival, pest populations and their associated damage could be reduced. Herbivores insect herbivores or even plant pathogens can be employed as biological control agents in order to control weeds ○ a program has been developed to control the invasive yellow toadflax in Alberta, Canada. A gall-forming weevil, Rhinusa pilosa, has been released in areas where the toadflax weed is abundant to reduce the prevalence of the weed. Through their feeding activity, these beetles have effectively reduced the presence of toadflax in these areas 43  Types of Biological Control ○ Importation/classical biological control Importation biological control used to be called classical biological control Introduction of non-native biological control agents to control non-native pest species in an expanded range Once these natural enemies have been determined suitable, they are imported under strict government regulation The goal is to ensure that introduced populations of natural enemies become self-sustaining. The natural enemies are intended to control, but not eliminate, an invasive pest species, to maintain a self-sustaining population that provides continuous control of the pest species without the need for further introductions Used for the alfalfa weevil in the US ○ Augmentative biological control active manipulation of populations of biological control agents to control pest species that can be either native or invasive control agents are not expected to become fully established in the area, and future management is necessary for continued control in later seasons. Inundative involves the release of large numbers of natural enemies to immediately reduce pest populations during or just prior to an outbreak ○ Corrective measure rather than preventative goal is for the natural enemy to quickly overwhelm the pest population and provide immediate pest control Inoculative involves the release of small numbers of natural enemies at timed intervals throughout the activity period of the pest species, and sometimes before pest activity ○ control agents are expected to reproduce to provide continued control by the progeny, but additional applications are typically necessary to support their populations. ○ Conservation biological control manipulation of specific variables in the environment to enhance the efficiency and persistence of natural enemies already present in 44  the ecosystem by reducing factors that interfere with the success of natural enemies, such as insecticide use ○ Practices such as pesticide application, tillage, and weed removal, can be limited to reduce disturbance of natural enemies present in the area or by enhancing resources necessary for their survival, such as food supply ○ provision of alternative hosts, food sources, or favourable overwintering habitats. ○ Managers can also support natural enemy populations by enhancing certain habitat features that provide refuge and resources for natural enemies Nesting sites or overwintering habitats Source of additional prey items or alternative hosts Pros and Cons of Biological Control ○ Pros: reduced impact on the environment compared to chemical controls Chemical insecticides can have very stable molecule structures Biological control agents are living organisms with a definite lifespan Partially addresses the growing problem of pesticide resistance Increased awareness of environmental impacts in farming practices Organic products command a higher market price (benefit to farmers) Can be cheaper to implement than traditional controls From stricter governmental regulations Also less likely to damage plants Classical/importation biological control can be very cost effective ○ Short-term costs are high, but self-sustaining natural enemies provide continuous control with no extra cost ○ Cons: can require more research on the biology and ecology of all species within the habitat compared to conventional pest management tactics more time to develop 45  Biological control agents are living organisms: may require additional resources for survival, such as alternate hosts or refuges activity may be affected by environmental conditions as well, such as temperature or day length they interact with other organisms in the environment. a lack of information about the pest, the control agent, and the surrounding ecosystem, can cause biological control to backfire ○ Happened with the Asian lady beetle, brought to NA to suppress aphid populations; outcompeted native ladybird beetles If the control agent has a broad diet breadth, its impact on the pest can be diluted through the consumption of non-pest species ○ Host-specific parasitoids and predators are preferable since they have adaptations to efficiently search out specific pests and will not attack non-target species. a restricted host range can mean that multiple types of biological control agents are necessary to control a complex of pests, which increases management costs broad-spectrum insecticides are unlikely to be used simultaneously with the release of predators or parasitoids since they may harm the biological control agents Much of the time the effects are not as instantaneous as with chemical controls Bad for high value crops, extremely damaging pests, or environments (greenhouses) where pest populations build quickly The number of available biological control agents in a certain region may be limited by regulations, which are ultimately set in place to prevent potential damage to the ecosystem Cultural Control ○ AKA Ecological management ○ involves purposeful manipulation of the environment to reduce the number of pests present and mitigate the damage they cause encompasses virtually all pest control methods that are not chemical controls, and do not manipulate natural trophic 46  interactions as is done in biological control. requires a thorough understanding of the biology, behaviour, and ecology of a pest species ○ Reducing favourability of the habitat can be achieved by eliminating suitable pest habitats, restricting pest access to resources, or by modifying environmental conditions Remove refugia Standing water for egg-laying by mosquitos Clean and seal cracks and crevices (roaches and bedbugs) Physical barriers Insect netting Tillage agricultural technique that mechanically disturbs the soil to prepare land for cultivation can also be used to expose soil-dwelling life-stages of an insect pest to predators and environmental conditions Remove overwintering sites removal of crop residue after harvest ○ Apple maggot Destroy alternate plant hosts ○ Manipulating timing disrupts the chronological continuity between pests and their hosts. Crop rotation different crops are planted in the same area over consecutive seasons. World best for insects with an immobile life stage Used for the Western Corn Rootworm Some insect specialists feed only on the host plant at a specific stage of development By changing the planting and harvest dates of annually produced crops, we can alter the crop’s phenology and hopefully reduce pest impact (Plant crops earlier so that they aren’t compatible with the insect’s life cycle) ○ Diverting pests Trap cropping is the practice of planting crops adjacent to the main crop that are attractive to the target pest to divert the pest infestation and dilute damage to the crop Insects in trap crops can then be controlled without worrying 47  about damage to the main crop often involves the use of semiochemical lures that help attract insects to the trap crop Synthetic pheromones can also be used to divert insect pests away from a protected resource. Intercropping involves the planting of multiple types of crops in the same area increase crop yield by making the most efficient use of resources on the land it can be purely physical, such as making host plants less apparent by hiding them under other crops with a higher canopy or a strong aroma The intercrop may be selected specifically because it is repellant to pest insects Not great for large-scale harvests Chemicals such as DEET provide personal protection by making humans and other animals less attractive to biting in