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ENT 101 - Insect-Human Interactions > Module 4 - Insect Locomotion > Flashcards

Module 4 - Insect Locomotion Flashcards

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1
Q

Passive Dispersal

A

When insect movement is aided by external sources
- wind, water, other organisms, planes, trains, automobiles

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2
Q

Passive dispersal on human-made structures has been linked to the introduction of many what?

A

invasive species

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3
Q

Why is passive dispersal highly advantageous? Disadvantages?

A
  • less energy required to move long distances
  • no control over the direction of movement so may not reach a suitable habitat or survive the journey
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4
Q

Phoresy

A

The passive dispersal transportation of an organism by a larger organism of a different species
- commensalism: the insect being transported reaches distant habitats while the carrier experiences neither harm nor benefit
- ex. mites and pseudoscorpions

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5
Q

Active Dispersal

A

An organism expends energy to move itself
- norm for most insects, increases chances that an insect will find suitable habitat
- requires efficient locomotory appendages and muscular control to move
- ability to assess habitat suitability requires a sophisticated nervous system with specialized sensory receptors

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6
Q

Marangoni propulsion

A

an escape mechanism used by rove beetles that dwell near bodies of water and are prone to falling in; excrete a mix of hydrophobic chemicals reducing the surface tension of the water and propels them back to land faster than they are capable of swimming.

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7
Q

Do insects have more muscles than humans?

A

Yes, each body segment contains its own musculature

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8
Q

Apodemes

A

Ridges of thickened cuticle on the inner surface of the exoskeleton to which muscles are attached

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9
Q

Resilin

A

allow flexibility of the muscle attachment site, elastic proteins
- common at joints such as wings and legs

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10
Q

What makes the musculature more efficient than that of larger animals?

A

The small size of insects makes their musculature more efficient because of the relationship btw power and mass.

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11
Q

Many larval insects have a relatively soft integument, to which muscles are attached. How are these insects moving?

A

Using a Hydrostatic Skeleton which functions with turgidity in place of rigidity.
- utilises the incompressible nature of the hemocoel fluid to oppos muscle contractions in the body wall
- since the hemolymph is incompressible, muscle contraction in one part of the body causes extension in a relaxed part of the body
- sequential waves of muscle contraction and relaxation allow directional movement of the insect which can be aided by hooks or mouthparts

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12
Q

How many legs do hexapods have?

A

6
- located in pairs on each of the 3 thoracic segments; prothorax, mesothorax, metathorax

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13
Q

What are the six segments of each leg?

A

Most proximal segment is the Coxa, then the Trochanter, Femur, Tibia, Tarsus, and Pretarsus
- the musculature to move the whole leg attaches from the sternum to the coxa, while separate internal musculature in each segment allows them to be moved independently

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14
Q

Tripod gait, Retraction, and Protraction

A

TRIPOD GAIT: 3 legs (the fore and hind legs of one side and the mid leg of the opposite side) remain in contact with the ground during walking; very stable motion

RETRACTION: the motion of the 3 legs pushing the insect forward

PROTRACTION: the motion of the other 3 legs being lifted off the ground to move forward

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15
Q

What is the most basic form of insect legs called?

A

Cursorial Legs (or running legs)
- elongated profile allows a long stride length
- well-developed femur and tibia used to propel the insect
- distal leg segments are slim to reduce wt and increase stride frequency
- combo of increased stride length and frequency allows rapid movement over the ground
- legs have been modified for use in a variety of enviros

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16
Q

Raptorial legs

A
  • example of a non-locomotory adaptation of legs
  • modified for grasping and holding
  • tibia and femur feature prominent spines to assist the grip
  • ex. Mantises
  • occurs most often in forelegs
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17
Q

Fossorial Legs

A
  • forelegs modified for digging with a flattened, enlarged, and hardened tibia that have tooth-like projections to assist with movement of soil
  • tarsi highly reduced so they don’t impeede digging
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18
Q

Saltatorial Legs

A
  • jumping legs
  • femur and tibia are greatly enlarged as they contain powerful muscles that store and rapidly release large amounts of energy to launch the insect
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19
Q

Natatorial legs

A
  • specialized legs for swimming
  • typically the mid or hind legs, and the leg segments are generally flattened with rows of setae or hairs to act like oars
    -legs are rotated in a particular pattern while swimming such that SA is maximized on the power stroke and minimized on the recovery stroke for efficient movement through the water
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20
Q

Prolegs

A

Locomotory appendages of some larvae groups
- Prolegs, or larvapods, are modified extensions of the body wall
- ends of these lobe-like extensions often bear hooks called crochets to improve grip on the substrate
- not “true” legs since they are not attached to the thorax and do not bear the 6 segments of true legs since they are not derived from the same structures

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21
Q

What are the 2 major groups of winged insects?

A
  1. Paleoptera
  2. Neoptera
22
Q

Paleoptera

A
  • refers to the old or ancestral state of being unable to rotate the wings so that they can be folded over the abdomen; these insects hold their wings out to the side or vertically over their bodies
23
Q

Neoptera

A
  • means “new wing” and includes all other groups of winged insects
  • the wings of these insects have flexion lines that allow them to be folded flat over the abdomen
  • evolution of these lines of flexion is what distinguish the Neoptera from the Paleoptera and come with several advantages
24
Q

What distinguished the Neoptera from the Paleoptera? What are the advantages?

A

Evolutions of lines of flexion
- wings are protected from physical damage when held against the body and insect is more compact
- wings are only present in adult insects, although the development of the wings can be visible on some exopterygote hemimetabolous insects like dragonfly nymphs

25
Q

Wing Structure

A
  • most insects have 2 pairs of wings; the forewings are appendages of the mesothorax while the hindwings are appendages of the metathorax
  • wing membrane consists of two thing layers of tightly appressed cuticle and these membranous structures are supported by a system of veins
  • the veins are hollow tubes of cuticle and contain tracheae, nerves, and hemolymph
  • in addition to providing support, the veins allow nutrient transportation and gas exchange within the wing
26
Q

Ventation patterns of wings

A
  • patterns are often distinct which allows entomologists to use wing venation to identify different insects
  • more evolutionarily derived insects have lost many cross veins, which results in a more flexible wing that changes airflow around the wing
  • to maintain wing strength the longitudinal veins tend to be thicker in insects that have a reduction in cross veins
27
Q

Sclerites

A

Wings are articulated on the thorax through hinged joints called sclerites, which combine cuticular plants with elastic structures to provide the necessary mobility to wings

28
Q

Tegmina

A
  • evolution of thick, leathery forewings
  • grasshoppers, mantises, cockroaches
  • used for protection, and symmetry in the beats of the forewings help steer the insect in flight
  • also fxn in sound production and amplification in orthopterans
  • can be variously coloured to aid in camouflage
28
Q

Hemelytra

A
  • half leathery, half membranous forewings
  • colour variation
  • additional protection
28
Q

Scales

A

Highly modified hairs, or setae, which cover both the upper and lower surfaces of the wings, and are set in sockers at an angle to the wing surface
- attribute the wide array of colours and patterns displaced on lepidopteran wings
- some specialized lepidopteran wing scales called androconia contain aphrodisiac-producing glands that secrete pheromones to attract a male
- lepidopteran wings serve many fxns: camouflage, mimicry, mate attraction, thermoregulation, protection

28
Q

Halteres

A
  • uniquely modified hindwings of true flies
  • knob-like structures are characteristic of the order Diptera
  • halteres are reduced hindwings modified into small, knobbed stalks which are used like gyroscopes to improve stability in flight
  • the sensory capacity of these reduced hind wings makes flies extremely agile in flight
  • beat during flight, although to a lesser degree than normal wings, and provide sensory info about the insect’s flight; speed and direction
  • CAMPANIFORM SENSILLA on the stalk of the halteres respond to perturbations in flight, wherever the stalk is deformed
28
Q

Elytra

A
  • forewings that are completely sclerotised to form protective structures
  • unique to coleopterans
  • can be completely hardened bc of the protein cross-linking that occurs in the cuticle during sclerotization
  • hindwings along power flight in beetles = weak flyers; elytra can provide some lift and stability in flight
29
Q

Aperous Insects

A

Wingless insects
- some do not have wings, others have lost their wings secondarily

30
Q

What are the 2 major mechanisms employed by insects to produce the basic up and down motion of flight?

A
  1. direct musculature
  2. indirect musculature
31
Q

Direct flight

A
  • the first type of muscular architecture is one in which the flight muscles attach directly to sclerites to power wing movement
  • in this arrangement, the direct flight muscles control both the up and down strokes of the wings directly by movement of the sclerites
  • up stoke is produced by contraction of a muscle attached proximally to the pivot point, while the downstroke is produced by contraction of a muscle attached distally
  • the direct control of the sclerites and wing movement allows some insects with direct flight muscles to control each wing independently for high agile flight
32
Q

Indirect flight

A
  • indirect flight muscles fxn by distorting the thorax to initiate wing movement, rather than being directly connected to the wing base
  • indirect flight muscles connect to ridges of cuticle within the thorax
  • DORSOVENTRAL MUSCLES produce the upstroke of indirect flight
  • DORSAL LONGITUDINAL MUSCLES produce the downstroke
33
Q

Synchronous Muscles

A
  • Insects that have a relatively low wing-beat frequency, less than 100 beats per second, can produce each of these wing-beats with direct nervous control over the flight muscles with one nerve impulse to drive each wing-beat. The muscles of these insects are termed synchronous muscles, as each contraction cycle is directly stimulated by a neural impulse
34
Q

Asynchronous Muscles

A
  • Many insects can beat their wings at a frequency of over 100x per second. Asynchronous muscles enable such high wing frequencies, as they do not require direct nervous stimulation for each contraction cycle.
  • Instead, stimulation of asynchronous muscles releases tension in one muscle which stimulates the contraction of the other, to perpetually drive the contraction cycle on with very few nerve impulses
  • THESE MUSCLES ONLY OCCUR IN INSECTS WITH INDIRECT FLIGHT
35
Q

3 Types of Movements of the Wings

A
  1. vertical motion
  2. rotated
  3. tilted in a figure-8 pattern
36
Q

Tools for studying insect flight

A
  1. Advancements in camera technologies
    - assisted researchers to determine the movement patterns of insect wings, but did not help with quantitative measures about the forces produced or experienced by insect wings
  2. Digital Particle Image Velocimetry (DPIV)
    - ability to track the movement of parker particles using high resolution imaging and recording systems
    - combined with measurements from sensitive strain gauges attached to the insect which allow the flow field around an insect wing and the forces to be precisely analysed
  3. Flight mills
    - constructed with a central post with a sensor
    - number of flight bursts, length of flight, distance flown, and speed can be determined using computer software linked to the flight mils
    - used to determine if treatments applied before or during flight influence flight propensity or distance
    - not used to predict the distance insects will disperse in nature
  4. Wind tunnels
    - used to study the response of insects to olfactory and visual cues
    - provides insights into the behavioural response of insects to various cues in flight
37
Q

Migration Criteria

A
  1. persistent movement away from the home habitat powered primarily by the animal’s locomotion, although many also use wind or air currents
  2. relatively direct movement toward a destination
  3. individuals are unresponsive to resource stimuli during migration, only stopping when necessary
  4. distinguishable pre- and post-migration behaviours
  5. physiological changes in the allocation of energy for different biological processes

*foraging, phoresy, dispersal, range expansion, mate finding, or human-associated movement is not migration

38
Q

Biological adaptations of migration

A

Suite of behaviours and traits that allow insects to offset the cost associated with migration and increase the probability of success are called a MIGRATORY SYNDROME

Reproductive diapause
- prominent in females, in which the development of eggs and sometimes the maturation of the repro system is postponed = OOGENESIS-FLIGHT SYNDROME
- many migratory insects aren’t capable of repro until after migration
- reduced levels of juvenile hormone provide the physiological mechanism for the delay in repro development associated with migration

39
Q

Physical adaptations of migration

A

Presence of wings in species which are otherwise wingless, and larger than average wings in species that are normally winged.

40
Q

Phases of migration

A
  1. Initiation
    - takeoff of migrants; begins migration
    - cues for takeoff include light intensity temperature, wind speed, and air pressure
  2. Transmigration
    - long-distance travel portion during which sustained flight occurs with few rest and feeding stops
    - some migrants are DIRURNAL (daytime-flyers); fly at low altitude; common amongst large-bodies and large-winged insects
    - other migrants are NOCTURNAL; fly at high altitudes to take advantage of stable and consistent air currents; use wind direction, moonlight, and the earth’s magnetic field to orient
  3. Termination
    - final phase
    - occurs when fuel reserves are depleted, with changes in photoperiod or temp, or with the location of suitable habitat
41
Q

Migration in locusts
- induced by…
- bold…
- increased…
- shorter…
- reduced…

A
  • Migratory grasshoppers are called LOCUSTS
  • The type of phenotypic plasticity responsible for the shift btw solitary and migratory forms in locusts is called POLYPHENISM
  • Phenotypic plasticity is the phenomenon whereby a single organism’s behaviour, physiology, or morphology changes based on enviro conditions, while polyphenism is a specific case that occurs when an organism has 2 or more discrete forms based on enviro conditions
  • migratory forms often have bolder or darker colouration
  • behaviour changes include aggregation rather than avoidance of conspecifics, flight during the day instead of night, and long-distance migrations
  • physiological changes: higher metabolic requirements, shorter lifespans, fewer eggs per egg pod
  • SWARM that feeds and moves as a unit
  • Locusts threaten crop production; insecticides applied to early swarms are the most commonly used control method and predicting when/where locust outbreaks will occur
42
Q

Monarch migration

A
  • conservation of this species is an international effort, benefits of understanding migration
  • monarchs are unable to diapause so cannot survive the winters or northern and central regions of North America; so they move south
  • Changes in photoperiod that preempt low temps prior to winter trigger physiological changes for the migration south
  • Oogenesis-flight syndrome is induced in migratory females so eggs are not produced before migration; triggered by a suppression of JH
  • Southward part of the migration is made by a single generation
  • Temps still drop enough at the overwintering sites that monarchs are largely inactive and aggregate to maintain a suitably warm microclimate
  • Changes in temp and photoperiod are used to terminate reproductive diapause, and initiate the return migration north
  • The return migration north is made by multiple subsequent generations (2-5); overwintered adults mate before initiating the trip north, during which they oviposit on milkweeds before death; next generation develops and continues this cycle as they head north
43
Q

Monarch navigation

A
  • Dependent on multiple interlinked systems which allow them to orient in a seasonally appropriate direction
  • Form a genetic memory that allows recognition of flight path, or landmarks to which they haven’t been exposed
  • Methods that monarchs likely use for navigation include a solar compass, a circadian rhythm, and air currents
  • Air currents propel them in a seasonably favourable direction and help them cover greater distance
    -Use an internal compass based on solar cues which can be calibrated with a circadian clock
  • Elements of the circadian clock are based in the antennae, and allow the insects to correct for the differeing positions of the sun
44
Q

Monarch Conservation

A
  • Populations have experienced declines, and the major threat has been to their overwintering and migratory habitats
  • Sites in Mexico and Cali have been removed or altered for urban development or logging; overwintering monarchs exposed to environmental extremes = mortality
  • Limitation in available overwintering sites also prevents normal movement of the overwintering colony
  • The treatment of milkweeds with herbicides may be beneficial for land managers and producers, however it reduces the availability of the monarch’s larval food-plants = declines in monarch abundance
  • Weather also had a major impact on monarch populations, as either unseasonably high or low temps can be detrimental or lethal to monarch development
  • Monarchs have garnered attention across North America, resulting in large-scale monitoring efforts, and the production of a multinational conservation plan
  • Conservation of forests in overwintering grounds and land use practices that maintain milkweed pops are being enacted across national boundaries to support the unique migratory phenomenon of monarchs
45
Q

Insect leg modifications

A
  1. cursorial legs
  2. raptorial legs
  3. fossorial legs
  4. saltatorial legs
  5. natatorial legs
  6. prolegs
46
Q

Insect wing modifications

A
  1. tegmina
  2. hemelytra
  3. elytra
  4. scales
  5. halteres

ENT 101 - Insect-Human Interactions (12 decks)

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