Movement of individuals from one place to another
Dispersal
benefits of dispersal
Escape from predation and unfavorable conditions.
Enables access to resources over a greater geographic range to reduce competition
Types of Dispersal
Passive Dispersal: Assistance from external sources or human-made structures
Active: Move from one location to another without assistance
Passive Dispersal leads to
Limitation where they have what? and a balance of
Little control over the destination and survivability
balance with high reproductive rate
Adapatations to capture wind currents such as long hair or silken thread
Ballooning behavior
Ballooning behavior characteristics
- Leave egg mass
- Climb to end of branch or shoot & drop down on silk strand
- Wait to be blown by wind to find suitable host
Active Dispersal Characterisitics
Increase the probability of finding suitable habitat
Normal mode for most insects
Adaptation for Locomotion is what?
Efficient locomotory appendages and energy, using specialized sensory and neuromuscular systems
Migration is considered what
specialized behavior
Migration types:
Uninterrupted flight patch
persistent movement
Migration Types:
Specific destination
Straight movement
Migration Types
separate from foraging behavior
unresponsive to most stimuli
Migration Type
physiological changes resulting in reallocation of resources
Observable pre- and post-migratory behaviors
Migration can occur across
multiple generations
This insect is considered a multigenerational migration?
green darner; migrated dragonfly in North America
Green Darner Adapative Strategy
Spreads reproductive effort across multiple, widely separated water
bodies
• Lowers the risk of predation, competition and
drought
Multigenerational Migration
3 types of generations
First generation is migratory, emerges
between February and May
and dies in North
Second generation emerges in North,
migrates South and dies
Third generation: offspring of migratory
individuals in fall,
is non-migratory and
emerges in South in November
Migration
A suite of pre-migratory behaviors that predispose to long movement
Migratory syndrome
Migration Cost/Benefits
- Migration begins before resource depletion, showing it’s anticipatory.
- There’s a trade-off between migration and reproduction.
- Energy is shifted from reproduction to fuel and muscle, reducing future reproductive ability.
Monarch Butterfly Migration
Characteristics
- Triggered by photoperiod and temperature, not population density
- Helps avoid harsh winters and follow milkweed availability
- Caterpillars eat only milkweed; adults feed on various nectar sources during migration
Monarch Buttefly
Adaptations
- Cluster for warmer microclimates, stay mostly inactive until spring
- Females enter reproductive diapause (no egg production before migration)
- Reproductive activity resumes before return trip; eggs laid on milkweed along the way
Monarch Butterfly Navigation
- Monarchs use genetic memory to find ancestral sites
- Navigate with a sun-based compass and circadian rhythms to adjust orientation
Monarch Butterfly Navigation Mechanisms
- Use geographical features and landmarks for navigation
- Follow chemical markers on plants left by past generations
Symbol of conservation in America:
Keystone species
Major threat:
Habitat destruction
Environmental
Constraints Issues
- Habitat loss from overwintering site destruction and fewer host plants
- Limited relocation ability due to reduced habitat
- Insecticides/herbicides harm survival
- Large-scale movement can lead to environmental damage
Migratory Locust
- Orthoptera species example of migratory pest insect
- Generalist herbivores (polyphagous), prefer cereals and grasses
- Major agricultural pests
- Show phenotypic plasticity—change behavior based on environment
Locust
- Increased population density triggers locust phase change via leg stimulation
- Serotonin release from seeing other locusts promotes aggregation
Swarm Formation of Locust
- End of dry season and rapid plant growth boost grasshopper numbers
- Overcrowding triggers shift to gregarious phase
- Swarms lead to mass egg deposition
Locust Swarms
- Locust swarms can cover hundreds of miles
- Climate change alters rainfall, triggering outbreaks in dry regions
- Rapid response needed—management is challenging