Arthropods III. Insect diversity: wings, larvae and pupae

Question 1

Describe wings

Answer 1

• evolved once in the insects
• NOT segmental appendages with articles; evolved de novo

Question 2

Describe termite wings

Answer 2

• only have wings at certain life history stages
• workers do not have wings

Question 3

Describe parasitic lice wings

Answer 3

• lost
• complete life cycle on host

Question 4

Describe the two theories for the origin of insect wings

Answer 4

• paranotal theory: wing develops from outgrowths of nota
• Endite-Exite theory: wing develops from exites of primitive leg segments

Question 5

Describe the paranotal theory

Answer 5

• proto wing
• notum
• sternum

Question 6

Describe the endite-exite theory

Answer 6

• sternum
• expicoxa
• proto wing
• subcoxa
• coxa
• exites
• prefemur
• femur
• tibia

Question 7

Describe powered flight

Answer 7

• cycle of power and recovery stroke
• need angle change of wing, and up-down flapping
• edge of wing towards front of insect is leading edge
• veins made of cuticle for strengthening function
• actively generates lift

Question 8

power stroke

Answer 8

down & forward

Question 9

recovery stroke

Answer 9

up and backwards

Question 10

Describe the innovation of powered flight

Answer 10

• only appeared four times in the history of life
• insects first (in mid-Carboniferous 330Mya)
• Pterosaurs in Triassic 225Mya
• Avialans in Jurassic 150Mya
• Bats in Tertiary 60Mya

Question 11

Describe powered flight in the Paleoptera - the basics

Answer 11

• controlled by direct flight muscles
• e.g. dragonfly

Question 12

Describe the direct flight muscles

Answer 12

• antagonistic muscles
• anterior and posterior direct muscles

Question 13

antagonistic muscles

Answer 13

contract in turn to give cyclic movement

Question 14

anterior and posterior direct muscles

Answer 14

control forward and backward movements

Question 15

Describe the Paleopteran flight - the specifics

Answer 15

• elevator muscles pull wings up
• depressor muscles pull wings down

Question 16

Describe powered flight in non-Paleopterans

Answer 16

• recovery stroke by indirect vertical flight muscles
• power stroke by indirect longitudinal flight muscles
• steering achieved by direct
  muscles
• sensors key to controlling flight

Question 17

Describe the indirect vertical muscles

Answer 17

• pull on roof of thorax
• wings rise, thorax widens & lengthens
• stretches longitudinal muscles

Question 18

Describe the indirect longitudinal muscles

Answer 18

• pull on anterior and posterior ends of thorax
• wings lower, thorax narrows and shortens

Question 19

Describe the likely evolution of powered flight

Answer 19

• likely from gliding ancestor
• gliding generates lift through fixed angle, non- flapping wing or lobe
• hinge, venation, muscle and respiration adaptions needed for flapping flight in insects
• folding of wings in non- Paleopterans opened up habitat opportunities
• asynchronous muscle
  evolved few times independently to increase wing beat frequency and allow a decrease in body size

Question 20

Describe the Crematogaster ant

Answer 20

parachuting

Question 21

Describe the Cephalotes ant

Answer 21

• gliding sensu lato
• directed aerial descent
• provided by glide angle

Question 22

Describe the Draco lizard

Answer 22

• gliding sensu lato
• classic gliding controlled by drag and lift resultant forces

Question 23

Flapping flight found in

Answer 23

hummingbird

Question 24

Describe the advantages of wings and powered flight

Answer 24

• mobility: food, niche, habitat space (microhabitats)
• dispersal: competition & speciation
• predator avoidance

Question 25

Powered flight is an evolutionary innovation that is

Answer 25

one reason for the huge diversity and abundance of insects

Question 26

Describe Ametaboly

Answer 26

- no metamorphosis - immature is a miniaturised version of adult - 1% of species

Question 27

Describe Hemimetaboly

Answer 27

- incomplete metamorphosis - immature (nymph) is a miniaturised, wingless version of adult - wings appear with new moults in late nymphs - 16% of species

Question 28

Describe Holometaboly

Answer 28

- complete metamorphosis - immature (young larva) is very different from adult - terminal larva - larva transforms into pupa (quiescent stage) - winged adult emerges from pupa - 83% of species

Question 29

Describe the metamorphosis of a locust

Answer 29

- hemimetaboly - 1st-instar nymph has a pronotum and a coastal margin of hind wing - 5th instar nymphe has pronotum, coastal margin, underside of hid wing, femur, tibia and tarsus - adult locust has coastal margin and upper surface of fore wing

Question 30

Describe the specifics of Holometabolous development

Answer 30

- adult form = imago - metamorphosis during pupal stage where larval organs are hydrolysed and reformed into adult organs - larvae moult several times to get larger during development, forming larval instars of different stages

Question 31

Describe the evolution of holometaboly

Answer 31

- enigmatic - pupae thought to be highly modified larval state

Question 32

Give an example of a holometabolous species

Answer 32

silkworm (moth)

Question 33

Describe the development and regulation of holometaboly

Answer 33

- hormonally controlled - most adult structures develop from imaginal discs

Question 34

imaginal discs

Answer 34

- clusters of embryonic reserve cells - unique to holometabolous insects

Question 35

Describe the advantages holometabolous development

Answer 35

- larvae and adults of holometabolous insects are ecologically very different - mechanism to control speed of development - diapause - parasitoidism in four families of wasps and flies

Question 36

Describe diapause

Answer 36

insects can pause development depending on environment (can be at any life stage)

Question 37

Describe the importance of niche partitioning in metamorphosis

Answer 37

- allows specialisation to different niches (e.g. mouthparts) - resource partitioning (e.g. different food sources) - avoidance of competition between different life stages - larvae for feeding and growth; adults for reproduction and dispersal

Question 38

Describe parasitoidism

Answer 38

- larvae parasitoids on host - adults free living (feed on nectar) - smaller than host - long term exposure - association leads to host death - every hexapod has its own parasitoid - hyperparasitoids - most important method for controlling insect populations

Question 39

Describe wasp parasitoids

Answer 39

use ovipositor to lay eggs in host

Question 40

Describe insect adaptations

Answer 40

- adaptations for a terrestrial existence - co-evolution with angiosperms - eusociality

Question 41

How are insects adapted for terrestrial existence?

Answer 41

waxy cuticle, trachea & spiracles, hyperosmotic excreta

Question 42

Describe eusociality

Answer 42

- Ants/Bees/Wasps, Termites & others - Honeybees form eusocial colonies of close relatives

Question 43

Describe insect coevolution with angiosperms

Answer 43

- phytophagous insects - pollinators

Question 44

Describe a phytophagous insect

Answer 44

Caterpillars produce enzymes to help them neutralise plant anti- herbivory toxins