ENTM 2050 final exam Flashcards
what percentage of insects are herbivorous?
30-35%
what are herbivorous insects called?
phytophagous insects
polyphagous insects
generalists that feed on many plant groups
-ex: aphids, grasshoppers
oligophagous insects
insects that feed on a few plant groups
-ex: monarch butterflies, caterpillars
monophagous insects
insects that feed on only one plant group
-ex: galls
what are the two types of plant defenses?
constitutive defenses, induced defense
constitutive defense
defenses which are always present
-ex: bark on trees (always devoting energy towards it)
induced defense
activated/synthesized only in the response to injury
-ex: toxins produced which harm feeding insects
what happens when an induced defense is triggered?
when an injury occurs (ex insect saliva enters the plant), there is
1. an up-regulation of genes for producing semiochemicals and/or other defenses, and
2. a down-regulation for photosynthesis and other metabolic processes
mechanical constitutive defenses
physical features of a plant which defend against insects (ex waxy or tough leaves, trichomes or scales, etc.)
-tough leaves impedes feeding due to high levels of indigestible fiber and lignin
-glandular trichomes: induce sticky substances which either trap or injure insects (toxic).
mechanical induced defenses
only occur after injury
-ex: leaf drop or colour change (on leaves affected by herbivorous insects)
pitching out
example of a mechanical induced defense
-only occur after injury
-some trees fill punctures in their bark with pitch (until it runs out); which is why bark beetles use mass attack
what are the two groups of chemical plant defenses?
primary and secondary metabolites
primary metabolites
-produce amino acids, nucleotides, lipids, and/or sugars as deterrents
-ex: some insects do not need high sugar concentrations, so they avoid eating high-sugar fruits
secondary metabolites
produce a diverse array of components as a deterrent (most are metabolic by-products)
-most are toxic to insects, some attract parasitoids, others are feeding/oviposition deterrents, etc
-ex: caffeine, cocaine, essential oils, aspirin
two types of secondary metabolites?
non volatile or volatile terpenes (does/does not warn the insect that it is toxic)
non-volatile terpenes
may be distasteful to herbivores (ex: minonene)
volatile terpenes
warns herbivores that the plant is toxic before feeding occurs (ex: menthol)
phytoecdysones
plant stepids that are chemically similar to insect molting hormones. Can interfere with/inhibit molting when ingested
what do acorn weevils use their “beaks” for?
used as a morphological adaptation
-allows them to create a passage into an acorn and lay their eggs into the acorn to allow their larvae to grow inside.
trenching
example of a behavioural adaptation in response to plant defenses
- insects will chew rings into leaves, which prevents the plant from releasing defensive chemicals into that area
detoxification as an insect response
by detoxification enzymes and saliva
-ex: webworms are able to metabolize toxins using detoxification enzymes
-saliva can be injected into plants to reduce production of toxins or break down the toxins
sequestration
the storage of toxic/distasteful secondary plant metabolites in tissues
-beneficial to the insect, as it is distasteful to predators, reduce competition, and may create a warning coloration
-seen in milkweed bugs, turnip sawflies, monarch butterflies
population level responses
move in large populations
-ex: pine beetles use aggregation pheromones to mass attack pine beetles (thousands of beetles can attack a single tree)
gall insects
insects which form a specialized plant-insect interaction in which the morphology of the plant is altered by the insect
-create “galls” which modifies the plants to grow around their developing eggs, providing food and/or protection for the inhabitant
what are the two processes involved in gall formation? how do they work?
- Initiation: galls can only be grown on living plant tissue
- Growth and maintenance: continued stimulation is needed to maintain the nutritive tissues in the gall. Growth ceases when insect development is complete
how many species of gall forming insects are known?
roughly 13,000
-from hemiptera, diptera, hymenoptera, and lepidoptera
what percentage of insects are predators, parasitoids, or parasites?
roughly 25%
what are some predator adaptations?
- modified mouthparts
-enlarged or modified mandibles - limbs
-modified to grasp and hold prey - camouflage
-ex: some have sticky hairs which allow them to cover themselves in dust and lint; helping them to blend into their environment
how do ant lions hunt?
excavate a pit in very fine sand/dirt, sit at the bottom of the hole to catch ants which fall into the pit. Can throw sand at insects at the top of the pit to make them fall further down into the pit
what are the range of cues which are used to locate host/prey?
- visual
- tactile
- auditory
- chemical (indirect and direct)
how do volatile chemical released by plants after injury function?
-can act as kairomones which attract other herbivores, or
-as kairomones to attract parasitoids and/or other predators
parasitoids
-parasitic while immature, free living as adults
-ultimately kill the host to complete its own life cycle
which orders is the majority of parasitoids found in?
-how many?
-mostly seen in hymenoptera, coleoptera, and diptera (however, seen in 7 orders)
-3/4 of all hymenopterans are parasitoids
-1/4 of all flies are parasitoids
what percentage of all insects are parasitoids?
roughly 10%
example of a parasitoid dipteran
tachinid flies
-primarily attack caterpillars and larval sawflies
-generalist parasitoids, attack any species with the right general body form/size
example of coleopteran parasitoid
staphylinid beetles: not all are parasitoids; but the ones which are parasitoids are ALSO predators (parasitoids as larvae, predators as adults)
-some parasitize larvae of pest flies
examples of hymenopteran parasitoids?
braconid wasps, ichneumonid, wasps, chalcid wasps
braconid wasps
mainly attack larvae of other holometabolous insects or hemipterans
ichneumonid
attack a large range of insects AND non insects (spiders and centipedes)
chalcid wasps
huge superfamily of parasitoids containing roughly 20 families. Most are very small.
ectoparasitoid
larval stage feed from OUTSIDE of the host. common in most concealed hosts
endoparasitoid
larval stage feed from INSIDE the host (adults lay eggs into the body of a host; larvae develops in the host then eats them from the inside out)
solitary parasitoid
one larvae develops on/in the host
gregarious parasitoid
multiple larvae develop in/on the host, results from multiple eggs
polyembryonic parasitoid
multiple larvae from ONE EGG develop in/on the host
(polyembryony)
idobiont
parasitoid which stops the development of host at the time of parasitism
-inject substances into host which paralyzes or impedes development
-seen primarily in ectoparasites and endoparasites of eggs and pupae
koinobiont
host continues development after parasitism
-may inject substances to alter immune system (ex polydnaviruses)
-primarily seen in egg-larval, larval, larval-pupal, and adult parasitoids
primary parasitoids
attack non-parasitoid host (ex herbivore, predator, etc)
hyperparasitoids
attacks other parasitoids
what are ovipositors on parasitoids used for?
allow them to pierce through hosts or other materials to get to their hosts (ex trunks of trees)
host hemolymph defence against parasitoids
if eggs are deposited into hemolymph, hemocytes adhere and form a capsule around the egg. The capsule can then melanize to prevent successful hatching by suffocation
parasitoid venom uses (5)
-sometimes used as a counter-defense against host defenses (hemocytes)
-some can paralyze the host, causing them to become immobilized which allows for easy egg oviposition
-suppresses immune response, ensuring the eggs are more likely to survive
-prevent molting (seen in ectoparasitoids; to prevent being shed off when molting occurs)
-severe metabolic alterations (most of the nutrients go to the parasitoids)
polydna viruses
-some parasitoids inject viruses into hosts (occurs naturally and replicates within the wasps ovaries)
-when injected, the virus incorporates itself into the host’s genome and begins replicating
-causes immune response to breakdown which disrupts encapsulation and prevents nutrient uptake
what are the two categories of insect adaptations to avoid being eaten?
- avoidance
- reactionary
examples of types of avoidance strategies
- crypsis
- warning/startle displays
- aposematism
- mimicry
crypsis (camouflage)
blending into the environment which you exist in (living or non living things)
-includes behavioral and morphological adaptations
warning/startle displays
-used to scare away predators
-ex: eye spots; mainly seen in lepidoptera
Aposematism
-warning colouration (warns predators of danger)
-bright colours/colour combinations seen on body
Mimicry
attempting to appear a different species or object
fighting back
-biting, stinging, aggressive behaviour, spines, etc
Sclerotization
hardened exoskeleton
-most organisms cannot pierce/break through the exoskeleton
Waxes/powders as morphological defense
-some insects are covered substances to defer predators
-ex: lady beetles do not like eating insects covered in waxes
stream drift escape behaviour
-seen in mayflies
-when feeling threatened, they will let go of a rock/substance in order to flee the predator
-get carried away by the current
Feigning death
playing dead
-seen in weevils
how do monarchs use sequestration of plant metabolites?
-monarch butterflies sequester toxins from the leaves they consume instead of metabolizing it. If a predator eats them, it will be harmed from the toxins and learn not to eat monarchs
trash collectors
Pile corpses onto their body to chemically mask their own scent
bombardier beetles
capable of initiating a chemical reaction which produces strong carbon dioxide to spray on predators
-pulsate the gas to avoid being cooked by the hot material
self production of toxins
-created through metabolic processes, and is stored until needed
-ex: blister beetles create a toxin which causes blistering on tissue which come in contact with it.
reflex bleeding
-squeeze hemolymph into certain parts of the body, allows predators to come in contact with the chemicals within the hemolymph without actually being eaten
social/gregarious defenses?
-strength in numbers
-stinging/venom (use alarm pheromones)
-soldier insects
model
organism/object which species attempts to mimic
mimic
species which mimics the model
observer (dupe)
potential predators to models/mimics
Batesian mimicry
-dangerous model, displaying warning colouration
-edible mimic, displaying warning coloration
-negative frequency-dependent selection: the more common the mimic, the less effective the mimicry
Mullerian mimicry:
-model and mimic are both distasteful or defenses + display warning coloration
-no clear identity of the model or mimic (either may be the model)
-rarity of each species has no impact on success (since they are both defended anyway)
visual mimicry
-form of mimicry most obvious to observers
-ex: tephritid flies mimic spider predators by having a banding pattern on their wings which closely resemble the jumping spiders which feed on them. When threatened, they turn their back on the predator to show their wing pattern.
mimicry ring
a group of organisms within a close geographical area which have adapted to have similar appearances
Myrnecomorphy
the mimicry of ants by other organisms
-ex: spiders, bugs, flies, etc evolving to look like ants
Wasmannian mimicry
resembles a model along with which it lives. Mainly chemical
-ex: within an ants nest, you will find silverfish, spiders, etc. Which mimic ants.
Aggressive mimicry
share the same characteristics as a harmless species, allowing them to avoid detection by their prey
-ex: trash carrying insects
-mainly chemical
Reproductive mimicry
actions of the observer (dupe) directly aids the mimics reproduction
-mainly chemical
Automimicry
one part of an organism’s body resembles another body part
-ex: end of wing resembles their head. Can lose part of a wing, but not their head.
Example of chemical and Wasmannian mimicry?
-butterflies lay eggs on plants which are picked up and carried by the ants into their colony
-the eggs hatch and since the caterpillars smell like ants, they will be raised by the ants
Parasites
an organism that lives in or on another organism (its host) and benefits by deriving nutrients at the host’s expense
pathogens
a biological agent that causes disease or illness to its host. May also be referred to as an infectious agent
-includes: bacteria, viruses, fungi, protists, nematodes
-Bacillus thuringiensis (BT)
bacteria naturally occurring pathogen found in soil. Causes disease when ingested by insects.
-used as insecticides (live BT is sprayed onto leaves to kill insects. Very effective against herbivorous insects)
-also used in transgenic plants (ex BT corn; kills insects when ingested)
-american foulbrood
bacteria which causes infection of larvae (only susceptible within the first three days of life)
-occurs if they eat a host with this bacteria. Will grow in the larvae and eventually kill it
why are insect-virus associations important?
- kill/harm beneficial species such as honey bees
- Naturally control forest and agricultural pests
- Can be developed into biological insecticides to control pests
deformed wing virus
RNA virus in which affected cannot fly and have a shortened lifespan
NPVs (nucleopolyhedro viruses)
RNA virus which primarily impact butterflies and moths
-when the caterpillars are about to die, they climb to the top of a plant, and their virus-infected body droops down and infects other insects
-populations in caterpillars tend to build greatly, then crash and remain low for a long time until spiking again
fungi
Can cause mortality in insects when humidity is high
-does not require ingestion
-before dying, insects will climb to the top of a plant, to allow the spores to be dispersed from the body
-Cordyceps: many species which each attack one species of insect
Nosema ceranae
Microsporidians found in honey bees
nematodes
small, parasitic roundworms
-kill their host by releasing bacteria into the body cavity
-some cause mortality, some do not
-most require very moist conditions (commonly seen in soil)
-can be used as an insecticide, as some target pest species