Of course, not all members of the insect family are pests of plants. Some of them are predators and parasites of other insect species. These can be the gardener's friends and go by the name of beneficial insects.

In nature, everything eventually comes into a balance unless some outside factor interferes. For every insect that eats on plants, there are other living organisms that feed on them.

Beneficial insects have many positives for the home landscape gardener. First of all, they can do that job that many people rely on pesticides to do. This can helps save money and prevent contamination of the environment with sprays. Once established, they do not have to be reapplied like pesticides.

Of course, there are also some difficulties associated with relying on beneficial insects to control your pests. As with any "organic" approach, they will not totally eliminate the pests. They will eventually form a relationship with their prey so that when pest numbers are high, beneficial insect numbers will rise to meet the challenge. However, they cannot eat them all or the beneficial insect would be out of business too. So, there are always at least some of the pests around resulting in some damage to the landscape plants.

Also, if you are going to depend on beneficials, you have to go all the way. Spraying pesticides for other problems on your property (or maybe even on adjacent properties) may kill off the beneficial insects along with the targeted pests.

PREDATORY INSECTS

Just like in the larger animal kingdom, predator insects make their living by killing and eating other insects. They are usually larger than their prey and do them in by chewing them up or sucking the juices out of their bodies. To develop fully, predators need a lot of food so they need large populations of their prey (i.e. plant pests) to survive and multiply.

  • Syrphid Fly Larvae - These insects are related to bee flies or hover flies. They are brightly covered with yellow and black stripes that look like yellow jackets. The larvae feed on aphids, scale and small caterpillars and can keep low populations in line.
     

  • Cecidomylid Larvae - Members of this fly family are predators of aphids, scales, thrips and spider mites. The adults are nocturnal and are not often seen. Larvae kill their prey by sucking out the body fluids. They go through about six generations per growing season.
     

  • Ladybird or Ladybug Beetles - These members of the Coccineilladae Family are good predators of aphids, scales, whiteflies and spider mites. About 400 species are native to North America and they are voracious eaters. More on Ladybugs...
     

  • Lacewings - Known for its lacy, net veined wings, this member of the Chrysopidae Family is a predator of aphids, mealybugs, leafhoppers, thripss, scales, spider mites and the eggs of moths. As the larvae develop, their sticky bodies accumulate dead bodies and debris from their environment which give them a strange appearance. There are two generations per year.
     

  • Predaceous Bugs - Some of the group of insects called "true bugs" such as the tarnished plant bug are plant pests. However, there are several others in the group that are predators. These good guys fall into two categories. The assassin bugs are large, brown or black bugs. They eat aphids, leafhoppers, scale and caterpillars. The second group called damsel bugs have the same menu of insects. Both types will also feed on other predators such as ladybird beetle larvae.
     

  • Predaceous Mites - These creatures feed on others of their kind, i.e. spider mites. If the population of the prey increases, these predaceous mites can reproduce rapidly to respond.

PARASITIC INSECTS

These are mostly species of wasps and flies that are smaller than the prey insects that they live on. Adults lay their eggs either on or in the victim. The larva feed on the juices and organs of the host. Unlike other parasites who do not kill their hosts, parasitic insects generally continue to eat until their host is dead.

The group of parasitic insects would include:

  • Tachinidae Flies - There are over 1,300 species of this type of fly in North America. Most of them are parasitic insects that feed on caterpillars and the larvae of beetles. They tend to be medium to large as adults with dull coloring and prominent bristles.

    Unlike most other insects, this group of flies generally do not lay eggs. Instead, the inject fully develop tiny instar larvae directly in or onto the host insect. When they are done feeding, only the "skin" of the host is left. They attack several different species of hosts.
     

  • Ichneumon Wasps - These slender bodied wasps have long antennae and permanently extended ovipositor (rear end egg depositer) which may be as long as the wasp's body. This is a very large size group of wasps that vary quite a lot. Generally, they are either internal or external parasites caterpillars, beetle larvae and sawflies.
     

  • Braconid Wasps - This is another group of parasitic, non-stinging wasps similar to the Ichneumon wasps but smaller. Their hosts include caterpillars, beetles (larvae and adults), maggots, sawflies and aphids.
     

  • Egg Parasites - Many of the tiny wasps also attack the eggs of members of the Family Lepidoptera which includes most caterpillars that turn in to butterflies and moths. They spend the winter inside the eggs of the host species.

Note: We have provided some general information and observations on this topic aimed at the home gardener. Before you take any serious action in your landscape, check with your state's land grant university's Cooperative Extension Service for the most current, appropriate, localized recommendations.

Types of Insects

"Name That Bug Page"

 

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