Entomophagous Insects – The Insect-Consuming Insects Predators and Parasitoids

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

Yellow Jacket Wasp Collects Many Insects for its Nest

Wasp Feeding on Birch Leafminer Larva

Sometimes Humans Are Active Predators of Insects, Too!

What is Biological Control? Biological Control is natural control that involves manipulation of predator populations to control pest populations in agro-ecosytems. “Biocontrol” has been an active area of applied population ecology for about 50 years. Today it is highly commercialized and is a viable addition to the arsenal used to combat pests. It is part of a larger approach called “Integrated Pest Management” or I.P.M.

“Beneficials” May be predators, parasitoids or pathogens May serve singly or in combination as “natural enemies” but populations often have to be manipulated. Reduce pest populations to economically tolerable levels rather than eliminating the pest. Environmentally compatible. Costs are comparable to pesticides.

Predators Commonly used predators include lady-bird beetles, green lacewings, mantids and predatory mites. Commercially available from insectaries.

Qualities of Good Predators Considerably larger in size than the prey. Why? Feed in juvenile stage as well as in the adult. Focused feeding habits - specific predators are better than general ones usually. Ability to switch to an alternative food source when prey populations are reduced. Must be able to adapt to local environmental conditions.

Examples of Predators Follow

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 Beetle

The Mealybug Destroyer – An Australian Import A member of the ladybird beetle family.

Green Lacewing Adult

Green 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 Adult

Other Well-Known Predators – Most Available Commercially Preying Mantids Some stink bugs (Hemiptera) Minute pirate bug ( “ ) Some nabid bugs Some mites are predatory

Why Aren’t All Insect Predators Effective As Good Biological Control Agents?

History of Control of the Cottony Cushion Scale in California

Parasitoids Generally a non-social wasp (braconids and ichneumonids are commonly used) or a tachinid fly Egg(s) are laid on/into host by female using a modified stinger (ovipositor) Larvae hatch and consume tissues of prey. Move to surface of prey, pupate and emerge 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 Caterpillar Prey

Wasp Eggs In Prey

Wasp Larva Emerging From Caterpillar Pupa

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

Aphid Mummies

Note numerous bristles on abdomen Tachinid Fly Adult Note numerous bristles on abdomen

Tachinid Eggs on Caterpillar Female Fly Attaches Eggs to Exterior of Body. They Hatch and Bore In.

Tachinid Larva Emerging Pupation Outside of Host

In this example, pupation is occurring inside the 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 Developmental Stages of Insects Egg Larva Pupa Adult

Egg Parasitoids

Annual White Grub Parasitoid

Nasonia Wasp Emerges From Dying 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 From Hyperparasitoids? A parasitoid attacks a host organism. What is the impact of a parasitoid population on a host population? A hyperparasitoid attacks a parasitoid. What is the impact of a hyperparasitoid population on a host population?

Parasitoids and Hyperparasitoids Associated With Cecropia

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