Insects Quiz 5
Name 3 conditions necessary for locust swarm formation and briefly describe how they are related.
1) Little rainfall that is not sustained leads to (2) sparse food. Thus large numbers of locusts are funneled into dwindling patches of remaining vegetation where they are forced into close contact with each other. This (3) crowding triggers a dramatic and rapid change in the locusts' behavior.
Order of colonization of dead bodies
1. blowflies (minutes to hours post-mortem)--prefer natural openings e.g. gunshots, stabbings 2. fleshflies (laid as larvae, predators on colonists)--prefer spots where blowflies are 3. dermestid beetles--some prefer moist tissue and others prefer dry 4. house flies 5. predators/parasites of earlier colonizers 6. beetles/moths--prefer skin and hair
Describe two potential downsides/drawbacks to pheromone-based communication systems in ants.
1.) Other predators can mimic these cuticular hydrocarbons and invade the nest, using it as a continuous food resource. Parasites and caterpillars go unnoticed as predators can eat freely in these nests, because the ants can't recognize they are there, chemically. 2.) They can lead to miscommunication that leads to the death of the entire colony. The example used in class was that sometimes ants will leave circular chemical pheromone paths, and the ants will literally keep walking in circles and die because they are confused
List and describe 4 reasons why conservation of species is important.
90% of pharmaceutical drugs are derived from plants and insects (thus, giving economic and health reasons) It's important to conserve some insects as they help control some insect pests Some insects are decomposers which are vital to our ecosystem We eat plants and some insects, which thus make them important to conserve
Describe the morphological specializations (ie..,e physical traits or coprophagous insects for exploiting that resource.
Antennae with chemoreceptors that allow them to 'smell' the presence of poop Specialized forearms/tarsi that they use to carve out and form sphere of poop to roll away for their larvae to feed on
How do do back brooding and non-back brooding water bugs differ in their behavior caring for offspring?
Backbrooders (derived trait) attend to their eggs above the water surface (carry eggs on back and bob in shallow water) where they may give their eggs enough oxygen, moisten them, shade them, and guard them against predation. Nonbackbrooding water bugs (basal trait) guard their eggs on vegetation at night, protecting the eggs and preventing them from drying out.
Why is there DDT in the blood of millennials?
Because we import our food, and DDT is still used in other places in the world that can't afford more expensive/less harmful ways of combating malaria. DDT is in the food we eat in the United States, but not in the food we grow here in the United States.
What are the benefits and drawbacks to nuptial gift giving among insects?
Benefits of nuptial gift giving: o More sperm transfer (more offspring are mine) o Better chance of offspring surviving (because since the female ate, the eggs are larger/more statistically likely to survive) Drawbacks of nuptial gift giving: o While the male is out looking for a nuptial gift, he is more vulnerable to predators bc he is distracted trying to find the optimal nuptial gift o More energy expended searching for large prey item o More time spent looking for prey item and not mating
What kind of disease vector is the malaria mosquito?
Biological
What traits make for an excellent insecticide?
Cheap and easy to produce How well it can kill insects → effectiveness and specificity at low dose Does not persist in environment
Briefly describe two different foraging communication systems used by social insects.
Chemical Trail (pheromones): (cuticular hydrocarbons)--> ants utilize cuticular hydrocarbons to "leave out" their paths from food sources. They are able to do this because they have direction vectors input in their memory that tells them which direction they are in relationship to the nest. Other ants use chemoreceptors on their antennae to follow these paths to food. Dance/Behavioral Method of Signaling: Certain bees, for example scout bees, perform a "waggle dance" to indicate distance and direction from the nest to the food source. Pollinators then use information gleaned from this dance (behavior) to locate the source of pollen + nectar. They pay attention to the duration and angle from the comb to the sun (perpendicular) to gauge distance + direction.
Why can't desert ants rely on pheromones?
Climate is too hot and dry -> the pheromones evaporate before they can be used as reliable sources of information towards the nest.
How do some predatory animals take advantage of social insects? Give two examples with your answer.
Concentrated resource in two ways—large numbers of prey (ant/bee/wasp, termite colony) in one place &/or consumption of sequestered resources (honey/pollen &/or larvae in nursery). Actually consuming the social insects or their resources: Bears consuming honey/pollen/grubs in comb. Anteaters consuming lg # of ants/termites Or taking advantage of their presence: Birds that hang out near army ants and catch insects fleeing in front of the advancing column
Why is DDT no longer used in the US?
DDT is lipid-soluble and therefore bioaccumulates in the storage tissues of organisms. This is mainly a concern for organisms that need to use these tissues under times of stress (e.g. birds in winter/reproduction). It has been found to inhibit calcium metabolism which causes weak eggshells, leading to losses in bird populations. It has also been shown to cause cancer in humans.
How did the use of DDT as a pesticide lead to a decline in songbird populations in the United States?
DDT may not be found on any particular organism in a lethal dose but as these organisms are consumed by animals farther up the food chain the amount of DDT in their tissues increases due to eating many individuals, each with a small amount. DDT in birds interferes with calcium metabolism making it difficult for birds to build thick egg shells. These eggs with thin shells tend to crack allowing the egg to desiccate enough cause the chick to die before hatching.
Why does this seem to make sense given the nature of what interests humans?
Day active, colorful, some have behaviors that or "interesting" to humans. These groups hit the trifecta.
How do desert ants navigate back to their nests?
Desert ants count their steps (cut off leg study) walking out, and then return to the nest based off that number.
How does knowledge of timing of colonization of a corpse by different insects help in solving a potential crime?
Different insects colonize a corpse at different times, thus based on which insects are present when the corpse is being examined, we can determine how long ago the body was murdered. For example, if flies are present we know it has been a relatively short time whereas if moths are present, odds are it has been awhile since moths eat the fingernails, hair, etc.
How does the 4 word term "energy flows, nutrients cycle" apply to trophic pyramids?
Energy passes (flow) from one trophic level to another by consumption of the lower level by the upper level. The upper level uses this energy in their metabolism (growth, maintenance, repair, reproduction). Once used to do work it cannot be used again. It leaves the biosphere as heat and cannot be recollected, compacted to useable form and used again - flows out of the system. Nutrient cycles—matter is not destroyed in the process of being used. It changes form as it passes from plants to animals then back into soil to be picked up by plants. Matter cycles through the biotic into the abiotic, then back into biotic portions of the ecosystem. However they describe energy flow it has to have the idea of "used once and lost to the system as heat". Energy can't be recycled. Nutrients as matter, remain in the system recycling between complex molecules manufactured by organisms using energy ultimately coming from the sun, then broken down into constituents when broken to release energy to run metabolic processes. Matter cycles from plants → herbibores → predators → detritivores/decomposers → nutrients in soil →plants again.
How do insects using carrion as a food source for their offspring help us determine the time of death of a body found in the woods?
If you know the amount of time usually required for an insect of a particular type to be attracted to a corpse, or at what stage of decomposition a particular insect is attracted, you can then back calculate time of death by knowing what insects have colonized the corpse. Flies arrive first, then beetles, then moths. Developmental stages of each insect species is also an important clue
Describe two costs of sociality.
Large group of individuals -->food source for predators Some individuals give up reproduction in favor of the group or mother that does all the reproducing. (deterministically unreproducing females)
For insects that feed themselves and their offspring on carrion (dead animals), list and briefly describe 2 aspects of development that are a direct response to using this ephemeral resource.
Lay larvae instead of eggs, cutting out the time eggs rest on resource before hatching. Hatch within female larvae and are ready to go consuming host immediately after laying Plastic development time: maggots may speed up development to pupate sooner as 'resource' quality deteriorates; results in a smaller adult than if they pupate later (in higher quality carcass, more flesh, fewer competitors, less waste product)
You know the method of information transfer between a scout bee and those bees that will be recruited to go collect the nectar/pollen discovered by the scout is the "waggle dance." How does it transmit "distance" from the hive to the pollen/nectar source? How does it transmit "direction" from the hive?
Linear length (or duration) of the dance on the comb gives an indication of distance from the hive Angle from perpendicular on the comb indicates the angle from the sun relative to the hive as the direction to the pollen/nectar source
What distinguishes a biological vector from a mechanical vector in disease transmission among insects?
Mechanical: picked up on feet (tarsi), may ingest/transmit when walking on food or regurgitate ingested material on food, contaminating it Biological vector: insect serves as host in life cycle of pathogen; chiefly blood sucking insects
Describe the two ways insects transmit disease.
Mechanical: they pick up pathogens on their feet/mouthparts when in contact with pathogen on food source or other substrate harboring the pathogen. Transmit the pathogen when they walk or feed at another location by physically touching another substrate. Biological: the insect serves as a host for part of the pathogen's life cycle. Ex.) Mosquito and malaria parasite → malaria parasite completes part of its lifecycle in the fly before being transmitted to a 2nd host when the mosquito takes its next blood meal. The pathogen then continues its life cycle in the 2nd host before returned to the mosquito again when another mosquito takes another blood meal.
How do insects colonizing the remains of a homicide tell us how long ago the victim died?
Order of colonization: various insects arrive at different times, some early after death, some later after death, specializing on different stages of decay. Depending on what insects have colonized the cadaver and which have not, we have an approximate time of exposure (and possibly death) of the cadaver to insect colonization. Rate of development: we know how fast various insects develop at a given temperature. By knowing what stage of development various insects are in, we know how long ago they found the corpse.
Describe the evolution of pesticide resistance in an insect species. Is it a trait that is pre- existing in the pest population or does a previously sensitive population become insensitive or resistant to the pesticide in response to application of the pesticide?
Pesticide resistance is a product of evolution. Insects can begin to detox the pesticide over time, have a change in chemical receptors involved with the pesticide, or change their behavior according to the pesticide. In this way, through mutation and directional selection, the pests become resistant to the pesticide in response to this application
Why do many of our effective pesticides/insecticides come from compounds found initially in plants?
Plants have long history (over 300 million years) of evolving defenses against herbivores. We have used anti-herbivore compounds isolated from plants to develop many different effective pesticides using the diversity of plants and the herbivorous insects they were protecting themselves from.
How is route following different from path integration in assisting an ant finding its way back to the nest?
Route following is merely following the chemical trail left on the way out away from the nest. Path integration means they have a directional vector in their memory that tells them approximately which direction from where they are to their nest. They constantly integrate which direction they are going relative to the direction back to the nest. Once they decide to return, they leave their trail 'out' and head back on the vector towards the nest.
What is the tradeoff with respect to "longevity" in labeling an insecticide "excellent" or "poor"?
Some insecticides remain in the food chain for awhile, such as DDT. As it moves through consumption levels, its concentration increases, thus, although it is cheap and effective, it's "longevity" causes it to be poor because it had poor effects on birds and their eggs If it lasts a long time, the pest for which it is intended may not be there any more...it may have been killed at the initial application or may not be there any more due to seasonality. By lasting a long time it may be killing insects that are not pests and that may even be beneficial, killing long after the pest outbreak has passed.
From the perspective of the plant, why are there plant pollination syndromes?
Specialized flower types for certain pollinators assures that more pollen from similar plant species will be delivered to the flower increasing the probability that some of that pollen will be from the same species of plant. Pollination syndromes promote the ecosystem function of positive growth rates for plant species w/ minimal loss of pollen going to vastly different speciesàno chance of pollinating those flowers.
Describe two life history traits that could make an insect species vulnerable to endangerment or extinction?
Specialized habitat requirements—easily disrupted life history by elimination of required host plant Climate change→ difficulty finding host plants, find mates, temp wrong for breeding/development, etc.
Worker bees do many specific jobs throughout their lives in the colony. List their jobs in order as they age from youngest to oldest.
Young workers: colony cleaning/maintenance (fecal matter/dead bees) feeding larval bees, producing wax/building comb Last stage of life: guard hive/foragers--finding nectar/pollen sources
Describe the term "ecosystem service".
any function that aids the energy flow/nutrient cycling of the ecosystem: pollination aids the population biology of plants, keeps them functioning as photosynthesizers, accumulating biomass that may be eaten by herbivores, etc. Decomposers return nutrients from complex organic molecules back into simple elements or smaller molecules that can be taken up from soil by plants and put back into the biosphere. Essential element is that organisms provide a service to other organisms that keeps the ecosystem functioning: positive growth rates of species at different trophic levels, passing energy/nutrients from one trophic level to another, recycling nutrients/elements in complex organic molecules back into simple compds or elements for plants to take up from soil.
What two or three taxonomic groups of insects do we seem to know the most about in terms of relative abundance over time?
butterflies, beetles, dragonflies - any other taxon that makes sense as being visible, interesting to human (beauty or economic importance)
The environment where the cadaver is placed impacts arrival time of insects
car adds about a week, shallow grave slows flies less than beetles, sun/shade impacts some species, freezing the body slows all aspects of decomposition
BT
companies placed genes in plants (BT) to form a crystal in the insect's stomach that rips the lining. Resistance cannot develop because the stomach lining needs to be thin to absorb nutrients. Non-target species are still impacted by BT corn because it's wind pollinated--it lands on leaves and is picked up by insects like butterflies. Resistance seen after 5 years within containment. Ways of developing BT resistance: 1. 1 gene—>1 product, but with multiple alleles, multiple variances of the gene are produced. A more effective allele will have more reproductive success 2. gene multiplication 3. efficiency of elimination of toxins 4. efficiency of not allowing toxins through exoskeleton 5. behavior/change in behavior
List and describe 4 general reasons why conservation of biodiversity is important.
economically important—components of prescription and over the counter drugs, pollination of crops, genes for domestic crops from the wild, etc. ecosystem function, known and unknown—for many won't know importance until it is too late ethics/morality—preserve for future generations of humans, every organism has a right to exist aesthetics—for beauty of nature, it is pleasing to look at (which connects to economical importance—vacations to parks, sightseeing, ecotourism)
List 3 traits of an excellent insecticide without any concern for non-target species.
inexpensive to manufacture, purchase, and apply easy to apply effective against intended pest & at low concentration/acre little/no apparent impact on vertebrates long persistence time
Why has DDT been banned in the US, but not abroad?
malaria is high in low GDP countries and DDT is cheap and effective at killing off mosquitos so we sell it to them to help their economy/fight off malaria
How does this list change when you consider non-target species?
needs to be more specific in action against intended pest short persistence time because short persistence time, timing of application to match with occurrence/life history of pest
Describe one important ecosystem service provided by insects.
pollination and detritivore (animal that feeds on dead organic material, especially plant detritus): aid the pop biology of plants either by increasing growth rate of plant populations → food for herbivores or detritivore—keeping manure from accumulating on surface of earth→ aids in breaking down organic molecules to simple ones that can be reused by plants. (1) pollination of flowering plants (positive growth rate of those plants by assisting fertilization of ovaa → seeds) (2) consuming dung/dead organisms, converting complex organic molecules into simpler compounds/nutrients that go back into the soil accessible to plants.
Describe 4 general reasons why humans should be interested in conservation (in general)?
self interest/economics: cmpds from plant/animals are used in Rx and OTC meds, pollinators for our crops, lumber, food, etc. Known impact of species on biosphere Unknown importance of species: next important drug/med; importance to ecosystem function Morality: every living thing has right to exist; following generations deserve to have fully functioning biosphere Natural beauty: we enjoy looking at nature, vacations, ecotourism, relaxation out of doors, etc.
What role does serotonin play in locust swarming? Why is this an important finding?
serotonin (neurotransmitter that affects things like mood/appetite/sleep) causes locusts to swarm. (shift to gregarious phase->increase in serotonin) People throughout the world used to use pesticides, like DDT, to combat the threat of locusts but people discovered that they could instead spray a compound on the gathering locusts that blocks their serotonin receptors to prevent them from swarming
Future of pesticides
shift to biocontrol of predators, parasites is the next option
Many of our food plants are pollinated by the Eurasian honey bee, an insect imported because it has a long coevolutionary history with those same plants. Why then does pollination of these plants drop in the absence of native bees in the habitats surrounding agricultural fields?
Eurasian honey bees change their behavior in the presence of native bees or other bee species. EAHBs change direction of flight when they encounter another bee species, increasing the time they spend in a patch of flowers they are collecting pollen from. The result is that they spend more time in an agricultural field, collecting pollen from more plants, hence pollinating more plants, than if they didn't encounter any other species in the field. They would get on a path through the flower patch and end up visiting fewer flowers.
Insects "trapped" flying in circles around street lights/yard lights appears to be maladaptive. Why does this happen?
Evolutionary, insects have adapted to maintain right angles in flight patterns to distant light sources at night, like the moon. The moon is far away so these angle measures at distance allow for enough flexibility in flight pattern that the insect can move relatively freely. However, yard lights are at close distance that insects can be trapped at right angle flight patterns and spiral close to the light. Its evolutionary orientation mechanism for light appears to be maladaptive since its not designed to move when light is in close range.
Specifically regarding insects, why should we be interested in conserving insect species?
Extremely important to our food production—direct impact on our food supply as result of pollination (fruits, seeds) and indirectly as growth from seed that requires insect pollinator (root crops like carrots) Impact on ecosystem services—nutrient cycling (detritivores, carrion eating insects, dung beetles) and population biology of plants thru their insect pollinators.
List and briefly describe a life history trait (different from development of larvae) exhibited during the adult stage of a carrion exploiting insect.
Females lay lots of eggs Ability to kill competitors (flesh fly maggots kill blowfly maggots) Adults may try to prevent other from laying their eggs on the same carcass
Describe two adaptations/specializations for carnivory/predation found in insects that were discussed in class, and give an example of each.
First adaptation is to become an ambush predator that seeks out insect trails and stealthily goes about picking off other insects-this is found in praying mantis and spiny assassin bugs Some predatory insects, for example cone-nosed bugs, have adapted to feed on blood meal where they feed off vertebrate blood
How might we know if a body had been moved or buried at some point after a murder?
Geographic distributions preventing access If a body has insects on it that do not occur in the habitat where the corpse is found you can infer that it was moved after colonization. If it is missing insects it should have in that particular habitat for the particular stage of decomposition → perhaps was at that stage of decomposition somewhere else, then moved. Burying prevents some insect types from being able to colonize a corpse. If they are present, the corpse was buried after they found the body, if they are absent, the body was buried too quickly for them to colonize the body.
Describe two reasons why some insect species have become endangered?
Habitat loss Introduced species Over harvest Hybridization pollution
How have some of these carrion eating insects been used, both historically and currently, to treat open wounds?
Historically fly larvae (maggots) have infested wounds of victims of battle. Too many wounded for hospital staff to get to all wounded—flies had opportunity to lay eggs → larvae consume dead flesh—wounds no worse than if medical staff could treat them right away. This observation lead to deliberate exposure of wounds to flesh eating fly larvae. Initially because it reduced dead rotting tissue that could lead to increase in wound size. Fell out of favor with the advent of antibiotics, but returned as a gentler method of reducing amount of dead/rotting tissue w/ less damage to healthy tissue than if medical staff mechanically tried to remove the tissue w/ instruments.
Insects can detect polarized light in some parts of their compound eyes, but not others. How is this capability distributed across the eye? Why has natural selection favored this arrangement?
Individual facets viewing the upwards portion (sky) of their field of view are sensitive to polarized light, but not those viewing the downward (ground) field of view The ground surface is extremely uneven. Polarized light reflecting from many different aspects of ground, vegetation would give tremendous number of polarized light flashes reflected upward into the eyes of insect that would be confusing. Better to deal with unpolarized light from the ground
The Red Queen in Alice in Wonderland says, "It takes all the running you can do to keep in the same place." How does this relate to insect and plant coevolution?
Insect and plant coevolution is essentially an arms race of constant mutation and counter mutation in which the predator (herbivore) and prey (plant) continue to evolve in response to one another in order to survive. One responding to the other's evolutionary changes, it seems like nothing is really happening (running in place). Since many pesticides are modified plant products, the red queen hypothesis explains why we expect resilience.
Describe two reasons why we should be concerned about potential insect extinctions.
Insects are decomposers and thus vital members to our ecosystem They act as natural pesticides (like ladybugs) who help to control pests Some perform important ecosystem functions such as pollination or predation. We don't know how important some species are at performing ecosystem functions. Won't know until they are gone.
Of all the insect species on the planet the only herbivorous ones that we've discovered switching to predatory have been found on islands. Why might this be so?
Island colonization sequence is constrained. Predators are less successful colonizers until plants and herbivores are well established (latter is predator food) Hence islands are often depauperate in predator species, less competition for a herbivore that switches to predator due to any appropriate mutation that changes behavior or physiology leading to a predator lifestyle compared to the mainland that has many more species of predators
How does the parasite get into a mosquito and how does it get out to infect a mammalian host?
It gets into the mosquito via a blood meal from an infected mammal where the mosquito ingests free-swimming parasite cells produced in the mammalian host. It gets out of the mosquito by exiting from the gut into the body cavity, swimming to the salivary glands, invading the salivary glands where it exits the mosquito and into the mammalian host when the mosquito takes its next blood meal If they tell you the parasite reproduces sexually in the mosquito and asexually in the mammal
We know very little about insect abundance over time in most places around the globe, especially compared to birds and mammals and even plants. Why is that?
It is much harder to achieve fossil records of insects. They are very small and thus decompose very quickly, moreover their skeletal structure differs greatly from birds and mammals. Insects do not possess large, hard bones like those animals do, which again make it difficult to obtain a fossil. It is much harder to achieve fossil records of insects. They are very small and thus decompose very quickly, moreover their skeletal structure differs greatly from birds & mammals. Insects do not possess large, hard bones like these animals do, which again make it difficult to obtain a fossil.
Why is the behavior of dung beetles rolling dung balls in a straight line away from the dung pile before burying it, evolutionary advantageous?
It minimizes risk associated with the dung pile. The dung ball + beetle has mass, so it costs energy to roll it away, so taking the shortest possible path via straight line lets the beetle go the maximum distance away from the dangers associated with the dung pile as quickly as possible. Dangerous egg predators, larvae predators, parasitoids are attracted to the eggs that were lazily laid directly in or under the dung pile, hence rolling the dung ball away from the large pile of dung reduces the risk of predation/parasitism to the egg/larva in the buried dung ball.
List and briefly describe two broad categories of defense from herbivory employed by plants.
Morphology structures: these are physical aspects of the plant that either make it harder for herbivores to ingest or digest the plant being tough, cellulose, lignin, silica; all make the leaf/twig tough to chew or pierce, spines/spikes/trichomes—interfere with getting at the plant. Trichomes are like tiny toothpicks that interfere w/ chewing, may be glandular and substances that fit category #2. Chemical defense: these are secondary plant compounds that the plant employs to either directly kill the herbivore or make it susceptible to predators toxins, resins, can kill, interfere w/ chewing (resins), interfere w/ digestion (tannins chelate proteins
Name the three types of symbiotic coevolution, and give an example of each occurring in nature.
Mutualism: (+/+) species derive fitness benefits from each other. E.g. ants / Acacia tree Commensalism: (+/0) one species benefits, the other is unaffected (hard to prove). E.g. a barnacle on a whale Parasitism: (+/-) one species benefits, the other is harmed. E.g. lice / mammals
Describe the evolution of pesticide resistance in an insect species. Is it a trait that is pre-existing in the pest population or does a previously sensitive population become insensitive or resistant to the pesticide in response to application of the pesticide?
Population resistance in population increases due to greater reproductive success of resistant pests. Insects either begin to detox the pesticide over time, have a change in chemical receptors involved with the pesticide, or change their behavior according to the pesticide. In this way, through mutation and natural selection the pests become resistant to the pesticide in response to its application. In initial population, most individuals have high to moderate levels of sensitivity to pesticide. Some resistance to total resistance is a rare trait prior to exposure to pesticide. With application, sensitive individuals either die or, due to impact of pesticide, have fewer offspring—fewer sensitive genes passed on to future generations. Those that are a little resistant to totally resistant to the pesticide leave proportionately more descendants than the sensitive pests.
How is the term "directional selection" applicable to pesticide resistance?
Presumably w/in a population of pests there are individuals exhibiting a range of sensitivity of to a pesticide from a rare few that are totally resistant to a rare few that are extremely sensitive, the bulk of the pop exhibits something in between the extremes. As the pesticide kills or weakens the more sensitive individuals, the more resistant individuals will survive better and leave more offspring containing their resistant genes. The most sensitive will be reduced in number, the resistant will be a greater fraction of the population, changing the composition from the original in the direction of a more resistant population.
Describe two benefits of sociality.
Provides a mode of communication through pheromones and other means for case of finding mates and defense Large numbers in colony means a lot of foragers and a large, stable food source
Why might natural selection favor the "black widow" trait of females consuming their mate post transfer of sperm?
Provisioning eggs is metabolically expensive. Once the male has passed on his sperm, if he lingers, natural selection favors the behavior of harvesting additional resources to provision either more eggs or the eggs that will be fertilized by the harvested male
What defense mechanism is used by Monarch butterflies to prevent birds from eating them?
The Monarch butterfly lays its eggs on milkweed plants, which contain a toxin that causes birds to vomit. This toxin is consumed by the caterpillar as it eats milkweed leaves post hatching on the plant. It is sequestered within cells of the caterpillar until it pupates to metamorphose int the butterfly form. During metamorphosis, the toxin is moved from the sequestered sites and incorporated into the exoskeleton of the butterfly. After eating a Monarch butterfly, either all of it, or just a bite of wing, abdomen, thorax, or head, a bird learns that the butterfly contains a poisonous compound and avoids eating other Monarch butterflies.
What traits among the first insecticides were at first thought to be good traits, but were soon found to be bad traits.
The ability to last a long time and be a strong pesticide were viewed as good traits originally, but were found to be harmful because a pesticide that lasted for a long time could have killed the target insect in its initial application, and still be working on non-target insects, such as the lady bug, that actually help control unwanted pests. These compounds could also become more concentrated over time through the consumption cycle. Another trait was mass dispersal of the insecticide via methods such as crop dusting. This seemed, in theory, a good way to disperse pesticides, but was later found to be ineffective at targeting pests, and often got blown to different locations by the wind, affecting plots not owned by the distributor or insects that were non-targets. (food contamination, killing other pest-controllers)
Why is Chagas Disease far more common in the subtropics and tropics than in the temperate zone when the vector, the conenose bug, a type of assassin bug, and the pathogen are present in both regions?
The behavior of the bug in the two habitats is different—in the tropics the bug defecates while taking a blood meal from a mammal host (humans too). When the human scratches the site of the bite eggs are picked up by the fingers and either transmitted to eyes or nose - infection follows, or are rubbed into the site of the wound caused by scratching until the site of the bite is now an open sore. The second host basically infects themselves, by scratching. In temperate areas the bug takes a blood meal and poops later, away from the site of the blood meal, thus removing the pathogen from the area and making self-infection very unlikely.
Describe 2 specific structural/morphological defenses that mechanically/physically interfere with insect herbivores.
The first morphological structure is silica: when plants produce silica it makes it harder for animals to ingest and digest the plant by wearing down a mammals teeth and insect mandibles Cellulose and lignin: make up the cell wall of the plant, can be increased in production by the plant to make it harder for herbivores to chew through and also no herbivore produces lingin so it also poses challenges for digestion of the plant material cellulose - very tough chemical, difficult to chew through lignin - same as cellulose silica - even more abrasive on chewing mouth parts resins - gum up mouth parts, sticky substance may trap entire insect trichomes - act as tiny "tooth picks" in mouth of chewing insect, interferes w/ chewing tannins—prevent digestion of proteins due to chelation by tannins
List two mechanisms whereby insects can overcome plant chemical defenses and "keep in the same place".
The first way is to simply avoid ingesting the food and this can be through evolved mechanisms to detect dangerous plan compounds, or in rare cases on islands, evolving to become a carnivore Some insects can evolve digestive mechanisms from genes with multiple alleles to lessen the toxic effect of secondary plant compounds whereby their bodies can avoid absorption of the toxic stuff and break down the toxins more effectively otherwise
There are characteristics of pesticides that make them better or worse environmentally. Describe how such characteristics of the pesticide as "residence time" (how long it lasts in the environment) and "photosensitivity" (how easy it is to break down via sunlight) make a pesticide either environmentally "friendly" or "unfriendly".
The longer the residence of the pesticide, the more unfriendly it is for the environment. Take DDT for example. DDT not only lasts a long time in the food chain, but also becomes more concentrated. A sa result it had a negative effect on bird eggs. However, with the case of photosensitivity, the more sensitive the pesticide is the more short-lived it is making it a more environmentally friendly product.
There are characteristics of pesticides that make them better or worse environmentally. Describe how such characteristics of the pesticide as "residence time" (how long it lasts in the environment) and "photosensitive" (how easy it is to breakdown via sunlight) make a pesticide either environmentally "friendly" or "unfriendly."
The longer the residence of the pesticide, the more unfriendly it is for the environment. Take DDT for example. DDT not only lasts a long time in the food chain, but also becomes more concentrated. As a result, it had a negative effect on bird eggs. However, with the case of photosensitivity, the more sensitive the pesticide is the more short-lived it is, making it a more environmentally friendly product.
A common method of applying pesticide to crops is to 'broadcast' the compound. That is, apply it from some distance above the crop (e.g., from a crop duster airplane or a sprayer on a tractor). Describe two negative aspects of this method of pesticide application.
The pesticide is subject to wind drift which may not allow it to hit all the plants we want or even if it does hit, it may not hit in a great enough quantity We risk non-targeted species being hit such as ladybugs that naturally assist in controlling pests life
A common method of applying pesticide to crops is to 'broadcast' the compound. That is, apply it from some distance above the crop (e.g., from a crop duster airplane or a sprayer on a tractor). Describe two negative aspects of this method of pesticide application.
The pesticide is subject to wind drift which may not allow it to hit all the plants we want or even if it does hit, it may not hit in a great enough quantity. We risk non-targeted species being hit such as ladybugs that naturally assist in controlling pests life
Why would you predict that the Bay and Quino Checkerspot butterflies (subspecies of Euphydryas editha) are potential candidates for being rare in the first place and candidates for greater rarity, even extinction?
They live in a limited habitat (coastal sagebrush in California and northern Baja) and this area is experiencing high human populations and extensive development—limited habitat is being altered for human habitation.
What sort of life history traits might one expect to find in insects that lay their eggs on carrion?
This would include such things as number of eggs laid, stage of development when laid, development time of larvae, time to pupation, offensive/defensive ability against other insect competitors, etc. Carrion eating insects must lay a very high number of eggs because odds are most will be eaten due to other insects or even vertebrate competitors like vultures who eat the eggs when eating the flesh of the carrion. Carrion eating insects have become incredibly flexible in regards to pupating. They can pupate very quickly (10-14 days) because the carrion is an ephemeral resource (plasticity of development). Large number of eggs that hatch quickly May hatch within the female → she says larvae, not eggs, gets a head start on egg-layers Quick development time → resource may not last long Development plasticity → may pupate at 20% of adult size if resources become scarce May kill/eat larvae of competitors Some carrion beetles carry mites that eat fly larvae that would compete with beetle grubs
In dung beetles, describe two different strategies for using dung as a food source for their offspring.
Tunneling: this is where dung beetles tunnel underneath the dung patty directly and lay more larvae because because there is more resource close to the habitat of the larvae. They are at risk, however, of predators who know that there are a lot of larvae concentrated in these areas close to the patty. Rolling: this strategy might involve laying fever larvae, but is more secure because the larvae have a broot ball of dung and are being transported away by females who constructed the dung ball in an area safer from predators.
