ENTOM 2011 Exam 2

What percent of insects are herbivores?

50%

What are the “Big 5” orders that are mostly herbivorous?

Hemiptera, Coleoptera, Lepidoptera, Diptera, Hymenoptera

Monophagous insects

specialists that feed on a single plant species/plants in the same genus

Oliogophagus

species that feed on plants in several genera, but within the same family

Polyphagous

generalists that exploit plants in more than one family

Modes of plant feeding

leaf chewing:

leaf mining: feeding in palisade parenchyma

gall inducers: gall structures that arise from aberrant plant tissue growth

peircing/sucking: feeding/sucking on flowers, fruits, and seeds

What is Coevolution?

a reciprocal evolutionary change in interacting species

• species A evolves in response to selection by species B, and vice versa

Plant defense mechanisms

• low nutrient value

• physical defenses (spines, hairs, spurs, thorns, sand)

• repulsive phytochemicals

• inducible defenses

• “talking trees"

• infochemicals & plant parasitoid “communication”

Phytophagous insects

only 9/29 insects orders are phytophagous = plant defenses work once insects evolve to eat the plants, they diversify

What problems do phytopagous insects face?

1.) they obtain nutrients from nutrient poor food

2.) they must process & eliminate excess amounts of carbon in doing so

Physical plant defenses

physical barriers: toughness, waxes, resins

structures: thorns, trichomes, architectures

latex

Constitutive defenses

plant secondary metabolites are only present all the time

Inducible defenses

plant secondary metabolites are only present when herbivores are attacking host plant tissues

Protease inhibitors

produced by plants, block insect proteases making insects incapable of digesting plant proteins

Parasitism

a relationship between two species in which the parasite obtains its nutritional requirements from the body of the host

• the relationship is always detrimental to the host, beneficial to the parasite

Which orders are primarily parasitic?

Siphonaptera, Diptera, Hymenoptera, Strepsiptera (all or mostly endoparasites)

Ectoparasites

feed on the blood/sections of the host, generally do not kill the host, generally smaller than the host

Endoparasites (parasitoids)

generally live within host’s body, generally consume host’s organs leading to the host’s death, generally attack other insect/arthropod hosts

What biological problems do endoparasites face?

1.) respiration: how to respirate when in host tissue

2.) digestion/excretion: how to excrete nitrogenous waste when doing so will kill the host

3.) host endocrine system: how to isolate one’s system from a host

Hyperparasitism

when parasites attack other parasites & become hosts

Superparasitism

when hosts are attacked by multiple parasitic species

Polyembryony

when one parasitoid agg hatches into multiple of endoparasitic larvae

How do parasites use polyDNA viruses

certain groups of Hymenoptera females inject a virus into the host, causing:

• immune suppression

• developmental arrest

What percentage of insects are predatory?

10%

Mechanisms of prey location

sit and wait

active hunting: use visual & olfactory cues to locate prey

lures

Examples of predators in other orders

ephemeroptera: mayflies

plecoptera: stoneflies

grylloblatodea: ice/rock crawlers

Katydids as predators

they mimic the female cicada click to attract male cicadas to eat them

Extra oral digestion

involves injecting salivary secretions/digestive enzymes into a host & liquifying the innards. remains are withdrawn through piercing/sucking mouthparts

Microbes and insects

microbes provide defense against pathogens, parasitoids, and predators; usually by producing chemicals that provide defense against enemies

Paederus beetles (rove beetles)

• pseudomonas produces toxins (pederin) which protects beetle larvae from predators

• the endosymbiont is transmitted vertically from mother —> daughter

• when beetles brushed/crushed against skin, can cause paedrusderm

Philanthus triangulum (bee wolf)

symbiont: Streptomyces

• bacteria is applied to brood cell walls before provisioning

• bacteria is consumed by larvae & is incorporated into the cocoon, protecting from pathogenic fungi & bacteria

• emerging reacquire the bacteria by rubbing antennae on the exterior of the cocoon

Leaf cutter ants (tribe attini)

fungi: basidiomycetes

• fungi is cultivated within the nest & fertilized w/ plant materials

• vertical transmission of fungi by queens in “infrabuccal pockets”

• fungi relies on ants for propagation

• pseudonocardia & streptomyces grow as a biolayer on ants and prevent against escovopsis infections of ant gardens

Escovopsis

specialized parasitic fungal pathogen

Agriculture

the production/processing of any food & non food items for human consumption

Types of crops

• food crops: things we eat

• cash crops: tobacco, tea, coffee, sugar, spices

• field crops: grains (wheat and rice), fiber crops (cotton, flax, hemp)

• seed crops: plants grown for seeds

• industrial crops: grown for non-food purposes

Direct damage

insects eating/destroying the fruit of a plant

Indirect damage

Insects eating/damaging the leaves/others parts of the plant

Integrated Pest Management

integrating the use of chemical/cultural/biologically relevant tools to manipulate the movement of insects within a field

• only utilizing chemical control when target insects are present

Citrus greening (HLB)

insect vectored pathogen: asian citrus psyllid (diaphorina citri)

• infect using piercing/sucking mouthparts

• candidatus liberibacter (CLas): phoelem limited bacteria, disrupts normal transfer of nutrients

wide spread in Texas and Florida

Mitigation strategies for agricultural pests

1.) vector control

• insecticide (e.g., spraying timed w/ tree phenology)

• biological control

2.) development of new technologies

• peptides to target pathogen

• double stranded RNA to target pests

• development of tolerant/resistant cultivars through breeding

How do insects impact health?

• physical nuisance

• venom

• entomophobia

• delusional parasitosis

• direct parasitism

Vector(s)

an insect/related animal that actively/passively transmits a pathogen from one organism to the next

Malaria

host(s): numerous vertebrates (including humans)

pathogen(s): species of the Plasmodium genus (protozoa)

vector(s): species of the Anapheles genus are the main vectors of the human malaria

What makes a good malaria vector?

• frequency of feeding on people (behavioral)

• longevity of adult female (physiological/ecological/molecular)

• vetor population density (ecological)

• vector competence (physiological/molecular)

Sterile Insect Technique (SIT)

release of lab reared sterile males to compete w/ fertile local males

• pros: species specific, evolution of resistance is unlikely

• cons: low fitness of lab reared/chemically sterilized males is a major problem

Gene Drive

two types: population suppression & population replacement

• pros: the intro threshold is very low, modifications are (fairly) precise & controlled

• cons: difficult to limit spread or recall once released, resistance can still arise

Invasive species

non-native/alien to the ecosystem under consideration whose introduction causes/can cause economic & environmental harm or harm to human health

Honey

a saturated solution of carbohydrates

• about 18% water & 81.5% sugar

• some acids (gluconic acids)

• various phytochemicals

How is honey made?

1.) collection by foragers

• plant nectar from flowers

2a.) processing by workers

• chemical modification by honey bee enzymes (sucrase → sucrose, glucose → fructose)

• glucose oxidase breaks down some glucose → gluconic acid & hydrogen peroxide

2b.) more processing by workers

• dehydration to 18% water content

3.) Storage in combs

• cells capped w/ wax when full & dyhydrated

Active evaporation

regurgitation & exposure to air (a few minutes)

Passive evaporation

fanning to further reduce water content of honey in cells

Why is pollination important?

60% - 70% of all flowering plant species require it

35% of food production depends on animal pollinators

• includes apples, almonds, peaches, squash, coffee, alfalfa, cocoa

Wind pollination

mostly ineffective, most gymnosperms & angiosperms rely on it

Animal pollination

much more efficient if you can use a high fidelity vector, like an animal

• birds, mammals, insects

Biomass

total mass of organisms can vary based on # of individuals or the weight of those individuals

How do insects deal with extreme temperatures?

Option 1: find/make optional conditions, or avoid them

Option 2: tolerate extreme conditions

Option 3: sit it out