Locomotion - Aerial Flashcards
lec 3 - Peer
What are the different types of aerial locomotion?
Flight
Gliding
Ballooning
What is Flight?
Insects are the only invertebrates that have evolved flight (a key innovation in the evolutionary history of insects) - enabled diversification of this group.
Flight ability is variable across insect speciesThe wings are connected to the thorax via a complex join (the wing hinge shown below in fig. A)
The join contains resilin, a highly elastic protein that allows for rapid sustained movement. Insect wings are flexible and have multiple veins with circulating hemolymph.
Optimal function of cells in the wings requires that nutrients, waste and signaling molecules be transported into and out of the wings via the hemolymph.
Taxonomists used the configuration of the veins and specific landmarks (see areas within white dots or letters on the pictures below) to obtain important taxonomic keys used to identify insects.
Examples of flight in insects?
Wingless insects belong to groups that have secondarily lost their wings (e.g. fleas, some scale insects). Other wingless hexapods belong to primitive taxa (Apterygotes: Collembola, Protura, Diplura (bristletails) and Thysanura (silverfish).
Most insects have two pairs of wings (Odonata, Orthoptera, Hemiptera, Hymenoptera, etc.) (see left panel below)
But in several groups, the wings are reduced to a single pair (see right panel below)
In beetles (Coleoptera): the forewings (front) are modified as a protective dorsal shield (called the elytra) and the hindwings (rear) are the only functional wings
The hind wing is typically longer than the elytra and folds underneath it
In flies (Diptera): the posterior pair of wings are reduced to halteres (shown with red arrows) and assist with flight performance and stability
How does wing size affect flight?
Wing size affects flight aerodynamics (e.g. uplift, drag) and therefore, will affect the individual’s flight performance
Therefore, wing size is likely to be under strong natural selection; for example, particular species will have wing characteristics that are well suited to their lifestyle and/or habitat type.
What is wing loading?
the ratio of body mass (or size) to wing area provides a measure of the energetic costs of flying in an animal. The larger the wing loading, the higher the costs to fly as the insect becomes too heavy for its wings. It has been used widely for all sorts of insect species and birds.
Low wing loading (large wings relative to body size) is typically found in species that require long sustained periods of flight
But large wings are cumbersome in complex habitat structures such as dense forests. Wings will tend to be smaller in complex vegetation to increase manoeuvrability.
invertebrates with small wings with larger body will have a higher wing loading than a invertebrate with larger wings and a large body.
There are 2 types of flight mechanisms in insects:
Indirect flight mechanism
Direct flight mechanism
Explain the indirect flight mechanism?
Muscles are used to raise and lower the wings. The thorax deforms through this process causing the wings to move up and down.
What is indirect flight mechanisms characterised by?
- Two opposing set of muscles
- Flexible thorax
- Energy-efficient flight system
- Most insects
- Synchronous or Asynchronous flight muscles
What are synchronous muscle?
a nerve impulse is required for each and every contraction. This limits the rate at which the muscles can contract, because it takes time for the physiological processes associated with a nervous stimulus to run their course.
What are asynchronous muscles?
they do not require a nerve impulse for every contraction. Instead, a nerve impulse now and then is all that is needed to keep these muscles contracting with regularity (achieve very high wing beat frequencies: bees, flies, beetles). Wings beat faster than neural transmission.
What is the direct flight mechanism?
muscles are directly attached to the wings and serve to raise and lower them as well as to tilt their plane at different angles.
What is gliding?
Some species of tropical ants use a form of gliding to return to their home tree trunk when they fall from branches.
During the fall from a tree branch, a rapid adjustment in abdomen orientation (pointed towards the tree trunk) directs the path of the falling ant through the air in a steep glide ending at the trunk.
This has also been found in tropical arboreal bristletails (‘silverfish’, ‘fishmoth’, Order Thysanura).
What is ballooning?
Some spiders use their own silk to create silk draglines that catch the wind and allows the spider to move around.
There is need for a balance between the gravity effect (which creates down-lift) and a drag force from wind (which creates up-lift).
The velocity of the spider can change depending on body posture or body shape.
