Insect biology: lifecycles and development

Coleoptera common name + importance

Beetles, most diverse order, provide examples of almost everything we discuss

Diptera common name + importance

True flies, very diverse order, includes species with largest impact on humans (mosquitos) as well as ecosystem service providers

Hymenoptera common name + importance

Bees, wasps and ants.

Examples of insect social structures, not all highly social. sociality has evolved multiple times within this order, also important ecosystem service providers

hemiptera common name + importance

true bugs. includes many of the most important agricultural pests

lepidoptera common name + importance

moths and butterflies. larvae can be major pests and adults can be important pollinators. unique feeding mechanisms

blattodea common name + importance

cockroaches and termites. termites provide excellent example of sociality

Main features of apterygote insects

No wings- primitive

metamorphosis slight or absent

order: archeognatha

main features of pterygote insects

winged

metamorphosis occurs

contains all the orders that humans love to study

main features of exopterygote insects

simple metamorphosis

immature stages = nymphs

pupa rarely present

wings develop externally

nymphs and adults often feed on same food

main features of endopterygote insects (holometabola)

metamorphosis complex

immature stages = larva

larva assimilates food

pupa present

wings develop internally

types of insect larvae

eruciform (caterpillar)

campodeiform (crawler)

scarabaeiform (white grub)

elateriform (wireworm)

vermiform (maggot)

Ellen Can’t Screw Every Virgin

types of insect pupae

obtect (chrysalis)

exarate (none)

coarctate (puparium)

Occasionally everyone cares

Mechanisms of sexual reproduction

overt displays (species specific): fireflies, cicadas

attraction to resource (eg food): dung, carrion

pheromones (typically female)

swarms (mostly male):

copulation (direct except for apterygotes

Mechanisms of asexual reproduction

parthenogenesis

hermaphoroditism

polyembryony

outline parthenogenesis

development from an unfertilised egg

can be obligatory or facultative

virtually all orders have at least one asexual representative

highly successful means of rapidly exploiting favourable conditions

female only eggs: thelytokous

male only eggs: arrhenotokous

male and female eggs:amphitokous

outline hermaphroditism

male and female reproductive organs in the same organism

method of asexual reproduction

outline polyembryony

two or more embryos from one egg

outline ovoviviparity

egg and yolk = laid = hatch

outline pseudoplacental viviparity

embro (placenta-fed) —>laid/hatch ~simultaneously

outline hemocoelus viviparity

embryo in haemolymph

outline adenotrophic viviparity

larva hatches in female- milk fed —>laid—>pupariation

What are the environmental gradients involved in phenology

photoperiod: consistent recurring gradient = noise free signal

long day and increasing day lengths=good indicators of spring or summer

short day and decreasing day lengths = good indicators of autumn or winter

temperature=inconsistent/variable=noisy signal

warm or cold spell ≠ good indicator

Give an example of an apterygote insect

silverfish- archeognatha

give an example of a pterygote insect

mosquito

given an example of an exopterygote insect

dragon fly, termite

give an example of an endopterygote insect

flies, butterflies, bees, etc

outline eruciform

caterpillar

body cylindrical, short thoracic legs, pairs of fleshy abdominal prolegs

moths and butterflies

outline campodeiform

crawler

elongated, flattened body, antennae/cerci, thoracic legs adapted for running

lady beetle, lacewing

outline scarabaeiform

white grub

body rubust and ‘c’ shaped, no abdominal prolegs, short thoracic legs

june beetle, dung beetle

outline elateriform

wire worm

smooth, long, cylindrical body

hard exoskeleton

very short thoracic legs

click beetle, flour beetle

outline vermiform

maggot

body fleshy, worm-like, no head or walking legs.

house fly, flesh fly

outline obtect

developing apendages visible, held tightly against body by shell-like casing. often found enclosed within silken cocoon

butterflies and moths

outline exarate

all developing appendages free and visible externally

beetles, lacewings

outline coarctate

body encased within the hard exoskeleton of the next-to-last larval instar

flies