Entomophagous Entomophagous Insects – The Insect-Insects – The Insect-Consuming InsectsConsuming Insects

Predators and ParasitoidsPredators and Parasitoids

What is “Natural Control” ?What is “Natural Control” ?

Natural Control is the everyday occurrence of predation of one insect upon another. In so

doing, populations of predators effect populations of prey and vice versa.

This is analogous to the classic relationship between the arctic hare and

fox populations.

In the Natural World Predators Are Abundant and Are Always Searching For

a Meal

A Ground Beetle Attacking a Land Snail

Ground Beetle Attacking Ground Beetle Attacking CaterpillarCaterpillar

As you can see, ground beetles are not very choosy. They will eat about anything that they can overpower.

Forest Tent Caterpillar

Yellow Jacket Wasp Collects Yellow Jacket Wasp Collects Many Insects for its NestMany Insects for its Nest

Wasp Feeding on Birch Wasp Feeding on Birch Leafminer LarvaLeafminer Larva

Birch Leaf Miner

Wasp

Sometimes Humans Are Active Predators of Insects,

Too!

What is Biological Control?What is Biological Control?

► Biological Control is natural control that Biological Control is natural control that involves manipulation of predator populations involves manipulation of predator populations to control pest populations in agro-ecosytems.to control pest populations in agro-ecosytems.

► ““Biocontrol” has been an active area of Biocontrol” has been an active area of applied population ecology for about 50 years.applied population ecology for about 50 years.

► Today it is highly commercialized and is a Today it is highly commercialized and is a viable addition to the arsenal used to combat viable addition to the arsenal used to combat pests. pests.

► It is part of a larger approach called It is part of a larger approach called “Integrated Pest Management” or I.P.M.“Integrated Pest Management” or I.P.M.

““Beneficials”Beneficials”

►May be predators, parasitoids or May be predators, parasitoids or pathogenspathogens

►May serve singly or in combination as May serve singly or in combination as “natural enemies” but populations often “natural enemies” but populations often have to be manipulated.have to be manipulated.

► Reduce pest populations to economically Reduce pest populations to economically tolerable levels rather than eliminating tolerable levels rather than eliminating the pest.the pest.

►Environmentally compatible.Environmentally compatible.►Costs are comparable to pesticides. Costs are comparable to pesticides.

PredatorsPredators

►Commonly used predators include Commonly used predators include lady-bird beetles, green lacewings, lady-bird beetles, green lacewings, mantids and predatory mites.mantids and predatory mites.

►Commercially available from Commercially available from insectaries.insectaries.

Qualities of Good PredatorsQualities of Good Predators

► Considerably larger in size than the prey. Considerably larger in size than the prey. Why?Why?

► Feed in juvenile stage as well as in the adult.Feed in juvenile stage as well as in the adult.► Focused feeding habits - specific predators Focused feeding habits - specific predators

are better than general ones usually.are better than general ones usually.► Ability to switch to an alternative food source Ability to switch to an alternative food source

when prey populations are reduced.when prey populations are reduced.►Must be able to adapt to local environmental Must be able to adapt to local environmental

conditions.conditions.

Examples of Predators Examples of Predators FollowFollow

Twelve-spotted Lady Bird Beetle Attacks An Aphid

Close-up of Predator and Prey

Female Ovipositing on Leaf After Consuming Many

Aphids

First Instar Larvae Hatch From Eggs

Older Instar Larva Preying on an Aphid

Multicolored Asian Lady Multicolored Asian Lady BeetleBeetle

The Mealybug Destroyer – An The Mealybug Destroyer – An Australian ImportAustralian Import

A member of the ladybird beetle family.

Green Lacewing Adult

Green Lacewing EggsGreen Lacewing Eggs

Eggs Are Laid on Stalks to Lessen Cannibalism

Lacewing Larva Scouting For Dinner (in this case a

bollworm)

Predator Uses Sickle-Like Mandibles That are Hollow to Suck Out Contents of

Bollworm

A Short Time Later – Predator is Engorged and Prey is

Drained!

Flower Fly Larva and AdultFlower Fly Larva and Adult

Other Well-Known Predators – Other Well-Known Predators – Most Available CommerciallyMost Available Commercially

►Preying MantidsPreying Mantids►Some stink bugs (Hemiptera)Some stink bugs (Hemiptera)►Minute pirate bug ( “ )Minute pirate bug ( “ )►Some nabid bugsSome nabid bugs►Some mites are predatorySome mites are predatory

Why Aren’t All Insect Predators Why Aren’t All Insect Predators Effective As Good Biological Effective As Good Biological

Control Agents? Control Agents? ►??

History of Control of the Cottony Cushion Scale in California

ParasitoidsParasitoids

►Generally a non-social wasp (braconids Generally a non-social wasp (braconids and ichneumonids are commonly used) and ichneumonids are commonly used) or a tachinid fly or a tachinid fly

►Egg(s) are laid on/into host by female Egg(s) are laid on/into host by female using a modified stinger (ovipositor)using a modified stinger (ovipositor)

►Larvae hatch and consume tissues of Larvae hatch and consume tissues of prey.prey.

►Move to surface of prey, pupate and Move to surface of prey, pupate and emerge as adultsemerge as adults

Trichogramma wasp Pupae Covering Tomato Hornworm

Typical Posture of Ichneumonid Wasp Female Preparing to

Oviposit

After ovipositing, the wasps deposits a pheromone on surface that deters oviposition by a 2nd. female. Why is this behavior very adaptive?

Wasp Inserting Egg Into Wasp Inserting Egg Into Caterpillar PreyCaterpillar Prey

Wasp Eggs In PreyWasp Eggs In Prey

Wasp Larva Emerging From Wasp Larva Emerging From Caterpillar PupaCaterpillar Pupa

Trichogramma Wasp Ovipositing Into Abdomen of Aphid (Note egg at lower

left)

Aphid Mummies

Tachinid Fly AdultTachinid Fly Adult

Note numerous bristles on abdomen

Tachinid Eggs on CaterpillarTachinid Eggs on Caterpillar

Female Fly Attaches Eggs to Exterior of Body. They Hatch and

Bore In.

Tachinid Larva EmergingTachinid Larva Emerging

Pupation Outside of Host

Host Caterpillar Containing Half Dozen Tachinid Pupae

In this example, pupation is occurring inside the

host.

Sometimes Parasitoids Work Very Hard to Find Their Hosts!

Parasitoids Attack All Parasitoids Attack All Developmental Stages of Developmental Stages of

InsectsInsects►EggEgg►LarvaLarva►PupaPupa►AdultAdult

Egg ParasitoidsEgg Parasitoids

Annual White Grub Parasitoid

NasoniaNasonia Wasp Emerges From Wasp Emerges From Dying Flesh Fly PupaDying Flesh Fly Pupa

The following 5 slides illustrate a sequence from one generation to the

next.

Adult Wasp Hatches From Cocoon

Annual White Grub Parasitoid

Last Larval Instar of the Next Generation Exits from Host

Caterpillar

Larva Spins Cocoon – Dead Host at Right

Pupal Cocoon Completed

In nature, it turns out that different species of wasps occupy

different trophic levels ...

some wasps attack caterpillar hosts while other wasps attack

the wasps that attack the caterpillars.

How are Parasitoids Different How are Parasitoids Different From Hyperparasitoids?From Hyperparasitoids?

►A parasitoid attacks a host organism.A parasitoid attacks a host organism.►What is the impact of a parasitoid What is the impact of a parasitoid

population on a host population?population on a host population?

►A hyperparasitoid attacks a parasitoid.A hyperparasitoid attacks a parasitoid.►What is the impact of a What is the impact of a

hyperparasitoid population on a host hyperparasitoid population on a host population?population?

Parasitoids and Hyperparasitoids Associated With Cecropia

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