Types of Insect Predators and Adaptations

What are the problems/obstacles that predators face?

Find it, grab it, and ingest the food.

What is the predation pathway?

Encounter → Detection → Attack → Capture → Processing → Ingestion

A ________ must succeed at every step.

Predator.

A ____ only has to break one.

Prey.

What mode sets encounter?

Foraging.

Sit-and-Wait:

Wait for prey to arrive (mantis, ambush bugs, ant lion larvae).

Active Searchers:

Cover space (ground beetles, lacewing larva, coccinellids).

Vision:

Dragonfly interception of moving targets is predictive not reactive.

What is stereopsis?

3D vision, mantis use.

Chemical Cues:

Herbivore-induced plant volatiles (HIPVs), prey pheromones.

What purpose do mandibles serve in predators?

To hold and chew.

What are examples of attack and capture mechanisms (mandibulate predation)?

Raptorial forelegs (mantodea, strike in tens of milliseconds), Cursorial pursuit (tiger beetles, up to ~120 body lengths with stop-and-go relocation), and pitfall trapping (ant lion larvae).

What are examples of attack and capture mechanisms (piercing predators - Hemiptera)?

Mandibular and maxillary stylets in a fascicle, labium as sheath, saliva injected (paralytic venom plus digestive enzymes).

What are examples of attack and capture mechanisms (piercing predators - Neuroptera)?

Mandible and maxilla paired into sucking jaws (venom/enzymes injected through jaw canal).

What does the labium function as in attack and capture?

A jointed arm folded into the head (the odonate labium, works only underwater and at close range).

Digestion Mechanisms (Chewing Predators):

Gut digestion of solid food.

Digestion Mechanisms (Extra-oral Digestion):

Enzymes injected, prey liquefied outside of the body.

Primary Defenses (before attack):

Crypsis, masquerade, aposematism, mimicry, phenology, avoiding detection.

Secondary Defenses (after attack):

Escape, startle/deimatic display, autotomy, chemical defense, armor.

Aphid Defense:

Alarm pheromone triggers dropping and dispersal.

Bats:

Echolocation calls, up to ~100+ kHz.

Moths:

Tympanal ears tuned to ultrasound (Noctuoidea, Geometroidea, Pyraloidea, and others).

Moth Ultrasound Responses:

Evasive flight, tiger moths make clicks that warn, startle, or jam bat sonar.

Counter-adaptations to Moth Ultrasound:

Stealth echolocation, shifting call frequency.

What is the classic ecological theory?

Models assume a predator and prey that interact continuously, in mixed populations, with no delay, insects violate many assumptions (discrete generations, stage structure, ectothermy, spatial structure, dispersal).

Why are insects useful?

They test the models.

Lotka-Volterra x:

The size (density) of the prey population.

Lotka-Volterra y:

The size (density) of the predator population.

Lotka-Volterra a (alpha):

The natural growth rate of the prey population in the absence of predators.

Lotka-Volterra B (beta):

The rate of mortality of prey caused by encounters with predators (predation rate).

Lotka-Volterra Y (gamma):

The natural death rate (mortality) of predators in the absence of food (prey).

Lotka-Volterra & (delta):

The efficiency and rate of growth of the predator population through consuming prey.

Type I Functional Response:

Linear (filter feeders).

Type II Functional Response:

Decelerating, most invertebrate predators.

Type III Functional Response:

Sigmoidal, prey switching, learning, refuges.

Aggregative:

Predators move to dense prey.

Reproductive (numerical):

Predators increase by births.

What shrinks the lag between prey outbreak and predator increase (but not to zero)?

Short generation time.