Insect bio: phenology and functional morphology

outline phenology

the study of the timing of periodic plant and animal life cycle events and how these are influenced by seasonal and interannual variations in climate

these phenomena are very sensitive to small variations in climate and can be a useful proxy for studying climate change

what regulates phenology?

temperature

photo period

outline photoperiodism

clock phenomena to distinguish long days/short nights

noise-free cue to synchronise seasonal activities

identified in most organisms (plants, animals, insects, etc)

outline polyphenism in aphids

seasonal polymorphism

long days, aphids = viviparous parthenogenetic (only females producing live young asexually)

plants growing well, food supply good during long days- take advantage and grow population

short days = males + ovipare (reproductive morph of aphid = females)

egg stages survive the winter

outline migration in monarchs

decreasing day length = migration south

increasing day length = migration north

transgenerational

outline dormancy in insects

diapause: monarch butterfly have a period of diapause at the end of their migration

what are the different insect mouthparts?

sponging

siphoning

sucking

chewing

outline insect mouthparts

example of diversity in form and function

specific mouthparts adapted to feed on different substrates

different mouthparts can be modified to feed on the same type of food (liquid, solid, etc)

what are the two categories of insect mouthparts?

mandibulate (chewing)

haustellate (piercing-sucking, sponging, siphoning)

give an example of a biting and chewing insect

cockroaches

give an example of a piercing and sucking insect

mosquitos

stylet

give an example of a sucking insect

aphids

stylet

give an example of a spit and sponge insect

housefly

uses labellum

give an example of the mouthpart varations within an order

hymenoptera: wasps bite and lick, bees lick and suck (proboscis)

give an example of mouthpart variation within a lifecycle

lepidoptera: caterpillars chew (mandibulate), adult butterflys and moths siphon (haustellate)

give an example of functional morphology

Bees:

leg morphology

Bees have baskets on their hindlegs for pollen

sting (ovipositor) morphology:

queen bee: uses stinger to lay eggs, repeated use

worker bee: uses stinger to barbs to inject venom to defend colony

symphyta (sawflies) have valves adapted to saw and cut into plant tissues for egg laying

give an example of hearing sound

preying mantis

has an eardrum on the ventral side of the abdomen, detects echolocation calls of bats

give examples of sound production

stridulation in crickets, rubbing their wings together creates sound and attracts mates

cicadas use tymbal organs to produce loud rhythms for mating calls

how do insects detect photoperiod

through specialised photoreceptors in the brain and internal circadian rythyms

outline photoperiodic induction

insects using the number of hours of day or night to regulate seasonal cycles of activity, morphology, reproduction or development

is sexual reproduction always determined by photoperiod?

no, stress factors can trigger it- poor quality/limited plant sources, high population density for example

give an example of the synchrony of organisms under normal phenology

1. butterflies and host plants: when synchronised, larvae have access to fresh nutritious food during crucial growth period

2. bees and flowering plants: bees emerge in spring when flowers start blooming, bees can collect nectar and pollen whilst flowers receive pollination

3. aphids: appear when leaves are on plants and crops, can start colonisation. when aphids start feeding, ladybirds and wasps appear as they feed on them

what are the consequences of climate change on phenology?

it causes phenological desynchronisation between organisms

mismatches can cause the extinction of species:

• if plants bloom earlier due to temperature shifts, but pollinators (bees etc) remain synchronised with photoperiod, pollination fails

• if caterpillars emerge early due to temperature shifts, migratory birds who use photoperiod could arrive too late to feed on peak caterpillar pops.

why were early insects so big?

elevated oxygen levels supported their large bodies and metabolic rates (which needed high oxygen levels to sustain them)

passive diffusion of oxygen through their exoskeletons

lack of large predators, warm and humid climate, lush vegetation.

what is the advantage of emerging periodically?

example: cicadas

reduce the chance predators adapting and learning to hunt them effectively, increasing the chance that individuals will survive and reproduce.

give an example of convergent evolution

aphids and mosquitos: both adapted mouthparts designed for piercing and feeding, aphids for sap and mosquitos for blood

what are some mating behaviours insects display?

courtship displays-dragonflies

mating flights-dragonflies

sound production-crickets

pheromone release- moths

explain swarming behaviour for mating

insects swarm for mating purposes, ex mayflies and mosquitoes gathering in swarms during specific times of year to mate

often in specific locations ie near water

why are insects so successful?

• Exoskeleton

• Long history

• Short generation time AND fecundity

• Metamorphosis

• Adaptability to changing environments

• Small size

• Evolutionary interactions with other organisms

• Mobile winged adults (+ passive dispersal)

• Sociality