10. Mandibulata 2 - Insects

Question 1

Describe the evolution of matamorphosis. 7

Answer 1

1. no clear difference between extinction rates of holometabolous and hemimetabolous
2. little evidence, but probably ecological factors that led to huge number of insect spp
3. probably exploitation of plants
4. difficult to dislodge once placed
5. expansion into empty terrestrial niches as plants arrived
6. correlation of holomatabola and arrival of seed plants - more food sources?
7. trees and wings coincided - dispersal

Question 2

Describe the evo-devo evidence that related to the number of insect species there are 3

Answer 2

1. Damen el al, 2002 - ancestral gill became wings and spinnerets
2. apterous gene involved in wing production in insects and expressed in book lungs, tracheae and spinnerets in spiders
3. some gene, different functions

Question 3

What are the coeloptera? 10

Answer 3

1. originated 265m years ago
2. 350 000+ spp, 1/3 of all insects
3. beetles
4. forewing hardened into alytron, flies with hind wings hidden underneath
5. phylogeny still debated
6. 4 living suborders
7. 95% in suborder Polyphaga- herbivores
8. eariest were detritus feeders
9. beetle herbivory grew over time
10. few carnivores

Question 4

Describe insect evolution.

Answer 4

1. insects easily survived end-cretaceas extinctions
2. only one order went extinct in permian mass extinction
3. may families affected, some extinct
4. correlation between radiation of lepidoptera and angiosperm appearance
5. lepidoptera (butterflies and moths) eat leaves and suck nectar

Question 5

Describe early insects. 7

Answer 5

1. 196m year olf mandible found in rhynie chert
2. similarities with winged insects
3. flight may have evolved earlier than we thought
4. insects may have evolved in cambrian
5. this has been named rhyniognatha
6. we have another fossil that may be an early insect, but soft bodied and hard to identify

Question 6

Describe the palaeodictyopterida. 6

Answer 6

1. related to odonata (dragonflies)
2. extinct
3. died in end of permian mass extinction
4. gigantism linked with increasing o2 levels in carboniferous, but decreased with arrival of aerial predators
5. increased oxygen diffuse further into body
6. may have had aquatic nymphs

Question 7

What do we know about insects and extinction? 5

Answer 7

1. 4 tribes of long-tongued bee (xylocopinae)
2. modern groups are distantly related
3. some think only a few survived last mass extinction and remaining radiated out
4. diversification linked with eudicots (flowers)
5. question of, without insects ect., how were gymnosperms correlated? by wind

Question 8

What are the mecoptera/scorpion flies? 7

Answer 8

1. now relict group (once numerous)
2. about 600 spp
3. mostly predators or sacrophages
4. used siphon-like mouthparts to drink nectar produced by gymnosperms, perhaps - no flowers at time of evolution
5. insect must have played a role and been rewarded with something, poss. nectar
6. particular plant spp involved had big pollen, not wind dispersed
7. no direct evidence associated with fossils or amber, seed bearing parts of plant have been found

Question 9

What are odonata/dragonflies?

Answer 9

1. damselflies etc.
2. 330myr old
3. carnivorous
4. aquatic stages
5. adult forms in a few hours and bursts out of back
6. good predators - evert appendages - dragonflies
7. dragonflies have perpendicular wings and big eyes
8. damselflies have parallel wings and bulbous eyes
9. very agile in the air

Question 10

Describe odonataa mating. 5

Answer 10

1. male grabs female head, female curves round abdomen to form mating wheel
2. male penis at anterior of abdomen removes sperm from previous mates to reduce competition
3. guards mate for about 1 day, fly in tandem
4. nymphs may eat each other
5. mayflies survive for one day - all emerge at once to confuse predators

Question 11

What are the myrmelecontidae/antlions? 4

Answer 11

1. burrows and excavates a slope
2. insects that fall in can’t escape
3. antlion flicks sand up so insect falls in and is eaten
4. laid as eggs

Question 12

What are lacewing flies? 4

Answer 12

1. larvae are predators
2. silk eggs
3. duck-faced lacewing flies have an extended neck
4. may be due to sexual selection - we don’t know

Question 13

What are mantispidae/mantidflies? 5

Answer 13

1. small neurones
2. mainly tropical
3. some larvae are parasites on spiders/bees
4. not flies or mantids
5. some have predatory legs for grabbing

Question 14

What are hymenoptera? 13

Answer 14

1. mate while flying
2. all diploid/haploid but not all eusocial eg. sawflies
3. 300 000 possible spp, 130 000 described
4. second largest insect order after coleoptera
5. ants, most bees and some wasps are eusocial
6. the female is small, male is winged
7. hamuli are syanomorphy
8. flies have 1 pair wings and halteres (diptera)
9. halteres are rear pair - balance organs that move against movement of front wings
10. hymenopterans couple pairs of wings with hamuli - hook on leading edge of hind wing - fly like flies
11. no halteres
12. most wasps are parasitoids
13. parental behaviour widespread

Question 15

Describe ants. 5

Answer 15

1. 9000 spp described, may be up to 30 000
2. 130m yr old
3. derived from wasps
4. many variants
5. queenless ants exist
6. these are tougher and attack others to prevent egg laying