L13 Flight (unfinished)

Question 1

What is the most energy efficient form of flight?

Answer 1

Gliding,especially in orthoptera

Question 2

How does gliding work?

Answer 2

angle of airfoil in relation to air flow is called the angle of attack.
Greater angle of attack = greater lift generated.
Planes have 20 degrees angle, insects have 30 - 50 degrees.
If the angle is too great, airflow is disturbed and stalling occurs.
Also depends on the difference in air velocity above and below the wing.

Question 3

What helps airflow not be disturbed?

Answer 3

Bristles and hairs along wings help channel smooth airflow, to allow a higher angle of attack.

Question 4

What is a different method of flight?

Answer 4

Powered flight

Question 5

What are the stages of powered flight?

Answer 5

1. Downstroke - down and forward
2. Superination - twist
3. Upstroke
4. Pronation - twist

Question 6

how does more advanced insects wing pattern differ?

Answer 6

Less veins in wings so are able to twist more and generate more lift.

Question 7

what are axillary sclerites?

What other sclerites are there?

Answer 7

sclerotised plates at the base of the wing, with muscle attachments to the body and form a hinge.
Also closer to the bosy, there are internal subalar and basalar sclerites. These have a ligament attachment to the subalar and basalar muscles.

Question 8

What are 4 variables affecting flight?

Answer 8

1. Wingbeat frequency
2. Stroke angle
3. Stroke plane angle - anglebtw stroke plane and the vertical axis
4. body angle - angle between longitudinal body axis and the flight path.

Question 9

What are direct muscles and how do they power flight?

Answer 9

Connect directly from the pleuron (thoracic wall) to sclerites. Muscles act directly on the wing.
Wing hinges on a pivot, and contraction of one muscle pulls wing down, contraction of the other pulls wing up.
Most primitive form of wing musculature.

Question 10

What forms the ligaments attaching the muscles to the wing apparatus?

Answer 10

Resilin - highly elastic, 100x greater energy storage capabilities than muscle.

Question 11

how do indirect flight muscles power flight?

Answer 11

Powerful dorsoventral muscles run from Tergal plate to sternum.
When contacted pulls thorax tergal plate down and stores energy in deformed thorax wall.
longitudinal muscles then relax and plate pops back up, flipping to it’s former stable state. Releases energy and wings move down fast.

Question 12

What is synchronous muscle?

Answer 12

Insects that beat their wings less than one hundred times a second use synchronous muscle.
contracts once for every nerve impulse.

Question 13

What is asynchronous muscle

Answer 13

Insects that beat their wings more rapidly use asynchronous muscle.
Contracts more than once per nerve impulse.
Achieved by the muscle being stimulated to contract again by a release in tension in the muscle.
This can happen more rapidly than through simple nerve stimulation alone.

Question 14

What is the fastest Wing frequency of insects?

Answer 14

Mosquito - 300-550 beats/second. gives flight speed of 32 km/hour.

Question 15

Why have some insects evolved not to fly?

Answer 15

Flight is very energetically expensive, eg Tsetse fly only had enough energy in the hemolymph to fly for 20mins a day. Must find host very quickly.

Question 16

What impact does body size have on flight?

Answer 16

Larger flying animals have higher velociy, eg swans and Canada goose, v fast
If smaller, air feels more viscous, allows v small insects eg thrips have fringed wings and can drift about in air currents, not using much energy.
Flight is limited in larger insects by O2 availability and limits of the tracheal system.

Question 17

How did wings evolve?

Answer 17

Would be difficult for wings to evolve de nuovo, so probably evolved from other structures.

Question 18

what is the paranotal theory for wing evolution?

Answer 18

Upper carboniferous terrestrial palaeodictyopteran
(cockroach like creature), had 3 lobes extending from the thorax. Possibly original function for heat absorption, sexual selection.
May have evolved to become larger and then became advantageous in predator escape. ‘Flying squirrel theory’ - able to climb up trees and glide off.

Question 19

What is a problem with the paranotal theory for wing evolution

Answer 19

Difficlt to see how these structures developed muscle attachments for powered flight.

Question 20

What is the gill flap and flying fish theory?

Answer 20

Fossils from lower permian or a mayfly nymph show they have gill plates. these have muscle attachments and been seen to ‘row’ themselves through the water.
The flying fish theory suggests as a predator avoidance strategy they would leap out of the water and glide using their gill plates.