insect defences part 1 Flashcards
what is considered the first line of defence from predators
Hiding which employs a range of cryptic approaches such as mimesis and camouflage
what is meant by a cryptic approach
A cryptic approach in insect defense refers to a strategy employed by certain insects to avoid detection or recognition by potential predators. The word “cryptic” comes from the Greek word “kryptos,” meaning hidden or concealed.
what is meant by the term deimatic display which is emplyed as a secondary line of defence in insects
goal of startling or intimidating potential predators. The term “deimatic” is derived from the Greek word “deimos,” meaning fright. The primary purpose of a deimatic display is to startle or deter a predator momentarily, giving the prey an opportunity to escape.
what are the prey defence strategies and relate them to time costs
1) Fight
2) Run
3) Hide
= as you go down the list time costs decrease
outline predator foraging strategies and relate them to energy costs
1) active search
2) Trap
3) sit and wait
= as you go down the list energy costs decrease
give some examples of visual defences used by insects
colour and pattern evolved as part of a predator avoidance strategy
1) crypsis= disruptive colouration and countershading
2) mimicry = appearing like another organism
3) mimesis = appearing like an inedible object
4) aposematism = warning colouration
5) deimatic display = sudden display of bright colours or eye spots
6) deflection marks = small eyespots
= there can be overlap between the different types of visual defence
give examples of species which show crypsis in terms of disruptive coloration and countershading
colouration
1) lime hawkmoth
2) angle shades
countershade
1) Hummingbird hawk moth
2) smoky wave
give an example of species which show mimicry/mimesis
1) orange tip butterfly
give an example of a spp which uses deimatic displays
1) peacock butterfly
2) eyed hawkmoth
= use of eyespots
3)Large yellow underwing
= colour
give an example of spp which use deflection marks
1) small heath
2) purple hairstreak
3) elephant hawkmoth
give an example of a species which uses aposematism
1) cinnabar
2) 6-spot burnet
3) red and black from hopper
give some examples of spp which use batesian mimicry
1) large red belted clearwing
2) bee hawk moth
give an example of spp which use mullerian mimicry
1) hornet
2) buff-tailed bumble bee
what is the difference between mullerian and batesian mimicry
Müllerian mimicry occurs when two or more harmful or unpalatable species evolve to resemble each other.
Batesian mimicry occurs when a harmless or palatable species evolves to resemble a harmful or unpalatable species
what are chemical defences
defencive compounds of some type prodcued in nearly all insects (allelochemicals)
= vary in size and volatility, chemical class and mechanism of action
= can contain substances which increase effectiveness
how may defence compounds be delivered
1) exist passivley in haemolmph and urticating hairs
2) be secreted from limbs
3) be activle yejected or exploded from the body
4) occur as venom and administered via sting
outline passive toxins in terms or urticating hairs
= may have setae/spines along the body containing toxins from poison gland cells
- hairs fracture when touched and toxins spill out onto the body surface causing stinging or dermatitis erucism
outline chemical defences secreted from limbs
= common in coleoptera such as ladybirds or bloody nosed beetle
- usually secrete toxic oily haemolymph from leg joints
- haemolymph taste is bitter so predator spits out insect
aka reflex bleeding
outline the chemical defence which invloves activley ejecting
- Bombardier beetles eject mixture of
boiling-hot toxic chemicals, including
p-benzoquinones, hydrogen peroxide
and enzymes, from special glands in
posterior - Some Isoptera (Nasutitermitinae)
possess hose-like projections on head
that produce sticky fluid from glands - Abdomen tips of Formicinae ants
adapted for spraying formic acid (lost
stingers)
outline venom in terms of chemical defences in insects
Stings evolved from ovipositor in some
Aculeata (Apocrita: Hymenoptera)
* Eusocial species display altruistic
behaviour in defence of colony (loss of
stinger causes death)
* Venom contains cocktail of enzymes to
produce immediate pain, inflammation and
tissue breakdown
* Releases alarm pheromone
* Barbed stinger gets lodged in flesh and
continues to pump driving stinger further in
and releasing venom
outline some behavioural defences
1) avoidance
2) grooming
3) basking in sun = elevates body temp killing pathogens which cant survive above 30 degrees, UV radiation kills many microbes
what is thanatosis
aka death feigning
= tonic immobility and is an anti-predator tactic not needing movement
= insect may fall to the ground or tuck in legg/antennae
= common in beetles
= elicited by contact, restraint and substrate vibrations
what is faecal defence
Physical or chemical defence against natural
enemies
o Tortoise beetle (Chelymorpha alternans)
covers itself for protection
o Termites (Coptotermes formosanus)
incorporate faeces into nest wall to avert
pathogens
* Predator-prey interactions
o Anti-feedant by pine weevil (Hylobius abietis)
* Habitat location – cockroaches use faeces to relocate and return home
* Mate attraction by beetles, Hylotrupes bajulus
outline some physical defences
- Modified mouthparts and spiny legs
can be defensive - Some cuticular horns or spines can
be used to deter predator. - Body shape can be used to prevent
dislodging from their hosts. - Many insects make retreats
