Lecture 10 - Insect Origins & Flight

Question 1

What are the 2 proposed insect ancestors?

Answer 1

Crustacea and Myriapods

Question 2

Describe Crustacea anatomy

Answer 2

• have 2 more leg pairs than insects
• have 2 primary body parts: head & the rest
• most primitive have more body segments

Question 3

What groups evolved from a crustacean-like ancestor?

Answer 3

Non-insect hexapods and true insects

Question 4

Describe non-insect hexapods

Answer 4

• tiny, soft-bodied animals
• mouthparts internalized in head
• oldest fossil approx. 400 mya

Question 5

What is needed to fossilize insects?

Answer 5

• fine textured mud or fine volcanic ash
• anaerobic conditions
• encasement in sap (amber) or tar

Question 6

4 fossil types

Answer 6

• impression fossils
• mineral replacement
• amber
• asphalt

Question 7

Amber fossils

Answer 7

attempts to extract and sequence DNA from insects in amber

none have been duplicated despite numerous attempts

Question 8

Continental Drift

Answer 8

had profound impact on insect adaptations and distributions

Question 9

Devonian

Answer 9

400-350 mya
Evidence of damage on fossil plant material
conditions poor for fossilization

Question 10

Carboniferous

Answer 10

350-285 mya
extensive evidence of insect radiation
insects large bodied
few fossils from this period

Question 11

Permian

Answer 11

245-285 mya

first major climatic drying and drought

Question 12

Triassic

Answer 12

210-245 mya
all continential masses united in to Pangea
first diptera & hymenoptera fossils
dinosaurs much more diverse

Question 13

Jurassic

Answer 13

145-210 mya
age of dinosaurs
first earwigs
first mammals appeared

Question 14

Cretaceous

Answer 14

65-145 mya
pangea breaks into two: laurasia & gondwanaland
caused by huge asteriod strike
first social insects

Question 15

Tertiary

Answer 15

1.6-65 mya
first parasitic orders: fleas, strepsiptera, lice
diversification within birds, specifically flightless birds

Question 16

Wing Development

Answer 16

• Apterygota - w/o wings (feed primarily on decaying segments, trace of legs on abdominal segrments)
• Paleoptera - primitive wings (most primitive, can’t fold wings, lack 3rd wing muscle
• Neoptera - folded wings (folded over back, winglessness also common)

Question 17

Evolution of Wings - 4 Theories

Answer 17

• Flying Fish
• Flying Squirrel
• Thermoregulation
• Mating Display

Question 18

Flying Fish Theory

Answer 18

moveable thoracic gills, climbed out of water to feed & escape enemies, used gills to glide with flapping motion, gill plates enlarged serving as wings
Advantages: dont have to create new muscles & articulations, easy to shift positions
Disadvantages: reasons to leave water unconvincing

Question 19

Flying Squirrel Theory

Answer 19

developed expansions on thorax for gliding, developed hinges and muscles for flapping
Advantages: expansions of thoracic dorsal plates
Disadvantages: developing new muscle attachments & wing articulations, requires moving muscle attachments from elsewhere

Question 20

Thermoregulation Theory

Answer 20

Wing precursors were used to capture heat
Advantage: heat leads to aid in developing wing articulation & muscles
Disadvantage: ?

Question 21

Mating Display Theory

Answer 21

wings evolved as display structures to attract mates

Not clear how you go from display to flight